M1 NOTES: NORMAL STRUCTURE AND FUNCTION | NIGEL FONG 2012
A | GROSS ANATOMY
WITH NEUROANATOMY, EMBRYOLOGY & RADIOLOGY
CONTENTS
1 | Early Embryology
2
2 | Upper Limbs
CREDITS
.
Anatomy:
Moore, Grays, Snell
15
Embryo:
Langman, Moore/Persaud
3 | Lower Limbs
51
Neuroanat:
Fitzgerald, Goldberg
4 | Back, Spine & Spinal Cord
81
Radio:
See inside
5 | Thorax
100
Artwork:
Pearl Lee
6 | Abdomen
144
Notes:
Em, Liang En
7 | Pelvis & Perineum
203
8 | Brain, Head & Neck
238
M1 NOTES IN GROSS ANATOMY
1 | EARLY EMBRYOLOGY
CHAPTER 1: NORMAL DEVELOPMENT IN
1 | EARLY EMBRYOLOGY
!
!
1. OVERVIEW
!
A. TIMELINE
Overview
•
•
•
•
•
•
Week 1: Fertilization to implantation
: zygote, morula, blastocyst
Week 2: Bilaminar germ disc
: epiblast, hypoblast
Week 3: Trilaminar germ disc
: ectoderm, endoderm, mesoderm
Week 4-8: Embryonic period, differentiation & organogenesis.
Week 9-Delivery: Fetal period, mainly growth
Organogenesis is the critical period where the fetus is most susceptible and anomalies
lead to severe consequences
Expected date of delivery
•
•
= last normal menstrual period (counting from 1st day) + 40 weeks (9m + 7d)
Assumption: 2 weeks for ovulation & fertilization, 38 weeks for development
!
B. SUMMARY OF STAGES
!
NIGEL FONG 2011/2012
PAGE A2
M1 NOTES IN GROSS ANATOMY
1 | EARLY EMBRYOLOGY
!
!.!
NIGEL FONG 2011/2012
PAGE A3
M1 NOTES IN GROSS ANATOMY
1 | EARLY EMBRYOLOGY
2. THE GERM DISC
!
A. WEEK 1: FERTILIZATION TO IMPLANTATION
!
!
Fertilization & Pre-implantation
•
•
•
Fertilization, forming a zygote, usually occurs in the ampulla of the uterine tube
Cleavage of zygote forms successively smaller blastomeres
A morula (12-32 blastomeres) has an inner & outer cell mass.
•
Blastocyst appears around day 4
•
Nutrition thus far is from nutrients stored in the ovum and the external environment
Blastocyst
•
Outer trophoblast: forms placenta
•
Inner embryoblast: gives the embryo
•
•
Blastocoele: Fluid-filled cavity
Blastocyst implants into the endometrium
of the uterus around day 6 (see later)
Implantation depends on a delicate balance
btw estrogen & progesterone (to thicken the
endometrium. Large doses of estrogen (e.g.
birth control) disrupts this balance.
•
Disorders of implantation
•
•
•
•
Ectopic prenancy: Implantation outside of the uterus occurs in 2% of all pregnancies.
Common ectopic sites are the uterine tubes, ovaries, intestines, or the recto-uterine
pouch (of douglas).
Rupture of uterine tubal pregnancy or attachment of placenta to abdominal organs
results in hemorrhage, and is the main cause of maternal death in the first trimester.
Placenta praevia: Implantation in the cervix is compatible with proper development
of the fetus, but when the cervix softens in preparation for delivery, the placenta may
separate from the uterine wall, resulting in bleeding and the risk that the fetus would
lack oxygen and nutrients during delivery.
Treatment of placenta praevia involves early C-section and complete rest in bed.
NIGEL FONG 2011/2012
PAGE A4
M1 NOTES IN GROSS ANATOMY
1 | EARLY EMBRYOLOGY
B. WEEK 2: THE BILAMINAR GERM DISC
Continuation of implantation
•
•
•
•
•
•
!
Trophoblast differentiates into cytotrophoblast & syncytiotrophoblast
Multinucleated syncytiotrophoblast
erodes endometrial tissue facilitating
implantation.
Maternal blood fr eroded endometrial capillaries fills lacunar networks, establishing
primordial uteroplacental circulation.
Syncytiotrophoblast prod hCG, which maintains hormone secretion by corpus luteum
Cytotrophoblast grows to surround the syncytiotrophoblast and stop the invasion
Clinical: Failure of cytotrophoblast stopping the invasion can result in
- Molar pregnancy: fetus not developing but instead forming grape-like cysts
-
Choriocarcinoma: syncytiotrophoblast invades myometrium and metastasizes to
e.g. the lung, forming a cancerous mass
Bilaminar embryonic disc
•
•
•
Embryoblast
differentiates
into
epiblast and hypoblast.
Epiblast forms the floor of the
amniotic cavity.
- Cont. w amnioblasts that prod
fluid to surround the embryo
Hypoblast moves to surround the
primitive yolk sac (exocoelomic
cavity) and helps to nourish the
epiblast
!
!!!!!!!!!
!
NIGEL FONG 2011/2012
PAGE A5
M1 NOTES IN GROSS ANATOMY
1 | EARLY EMBRYOLOGY
12 days
Secondary yolk sac
•
•
•
•
13 days
!
Hypoblasts forms the extraembryonic mesoderm btw trophoblast & primitive yolk
sac (exocoelomic membrane)
Extraembryonic cavity (chorionic cavity) forms in the extraembryonic mesoderm
- Extraembryonic somatic mesoderm: lining covering cytotrophoblast & amnion
- Extraembryonic splanchnic mesoderm: lining covering yolk sac
Hypoblast produces additional cells that form a smaller secondary (definitive) yolk
sac within the old primitive yolk sac (exocoelomic cavity)
Germ disc connected to trophoblast by connecting stalk, which later forms the
umbilical cord
NIGEL FONG 2011/2012
PAGE A6
M1 NOTES IN GROSS ANATOMY
1 | EARLY EMBRYOLOGY
3. THE TRILAMINAR GERM DISC
A. WEEK 3: DEVELOPMENT OF THE TRILAMINAR GERM DISC
Gastrulation (formation of distinct germ layers)
•
•
•
•
Primitive streak appears in the median plane of the pear-shaped embryonic disc and
later becomes a primitive groove. This results from the proliferation and movement of
epiblastic cells to the median plane.
Differentiation of epiblast into ectoderm and endoderm: Cells leave the deep surface
of the primitive streak and displace the hypoblast, forming the embryonic endoderm at
the roof of the umbilical vesicle. Cells remaining in the epiblast forms the ectoderm.
Formation of mesoderm from ectoderm: Further invagination of cells from the
primitive streak forms a layer of mesoderm between the epiderm and endoderm
Hence epiblastic cells give rise to all 3 germ layers: ectoderm, mesoderm, endoderm
!
!
Buccopharyngeal & cloacal membrane
•
•
2 locations where ectoderm and endoderm are in contact (no mesoderm in between):
[cranial] Oropharyngeal (buccopharyngeal) membrane = future oral cavity
-
•
Prechordal plate forms btw tip of notochord and oropharyngeal membrane, it is
important for induction of the forebrain
[caudal] Cloacal membrane = future anus
-
Allantois: Pos wall of yolk sac forms small diverticulum into connecting stalk.
Serves as a reservoir for excretory products of the renal system in some animals but
remains rudimentary in humans, may abnormally persist as Merkel’s diverticulum
Formation of notochord
•
•
•
•
!
Invagination of cells fr primitive pit forms a
notochordal canal in the median line
Floor of notochordal process fuses with
embryonic endoderm, forming a notochordal
plate in communication w umbilical vessel.
Notochordal plate infolds again to form the
notochord
The notochord eventually develops into the
nucleus pulposus of the intervertebral discs
and is important in signalling axial
musculoskeletal development
NIGEL FONG 2011/2012
!
PAGE A7
M1 NOTES IN GROSS ANATOMY
1 | EARLY EMBRYOLOGY
B. OVERVIEW: DERIVATIVES OF GERM LAYERS
!
Ectoderm
•
•
•
Epithelial tissue: epidermis & derivatives (hair, nail, sebaceous glands)
Nervous tissue: CNS & PNS, sensory epithelium, pituitary gland
Connective tissue of head (lens of eye, enamel of teeth)
Mesoderm
•
•
•
•
Epithelial tissue: blood vessels
Muscle tissue: All muscles
Most connective tissue: bones, joints, cartilage, mesothelium (pleura, pericardium,
peritoneum), blood, suprarenal cortex, spleen, kidneys, gonads and their ducts
Mesoderm divided into [med-lat]:
- Paraxial mesoderm
- Intemediate mesoderm
- Lateral mesoderm: divided into parietal (somatic) & visceral (splanchnic) layers
Endoderm
•
Epithelial tissue: Gut and derivatives, i.e. GI tract, respiratory tract, middle ear,
parenchyma of tonsil, thyroid, parathyroids, thymus, liver, and pancreas.
NIGEL FONG 2011/2012
PAGE A8
M1 NOTES IN GROSS ANATOMY
1 | EARLY EMBRYOLOGY
C. EARLY DEVELOPMENT
!
The CNS and CVS the only 2 organ
systems that develop in the 3rd week.
Neurulation
•
•
Ectoderm overlying the neural plate differentiates into neuroectoderm and forms
the neural plate
Day 18: Neural plate invaginates to form neural folds, which then fuse into a neural
tube and separates from the ectoderm (fusion progresses in cranio-caudal seq)
-
•
Narrow caudal 1/3 forms the spinal cord
Broader cephalic 2/3 forms the brain
- Closure of ant neuropore occurs before closure of pos neuropore (by end of wk 4)
Neural crest cells migrate laterally as the neural folds meet, entering the mesoderm
-
•
Become sensory ganglia, sympathetic & enteric neurons, Schwann cells, cells of
adrenal medulla, cranial ganglia, melanocytes.
Clinical: Neural tube defects result in the failure of the neural folds to fuse and form
the neural tube.
- Failure to close ant: defects in brain formation, e.g. anencephaly
-
Failure to close pos: defects of spinal cord, e.g. spina bifida
Somite formation
•
•
•
Somites = segmented blocks of paraxial mesoderm
In 3rd week, the thick longitudinal paraxial mesoderm cell column differentiates,
condenses and divides into paired cuboidal bodies in a cephalocaudal sequence.
- Age of embryo can be determined by counting somites
Somites give rise to most of the axial skeleton, skeletal muscles, and dermis [see limbs]
NIGEL FONG 2011/2012
PAGE A9
M1 NOTES IN GROSS ANATOMY
Vasculogenesis
•
•
•
•
1 | EARLY EMBRYOLOGY
!!
!
Cardiovascular system develops early due to the urgent need for gas exchange and
nourishment as the embryo grows
Cardiovascular system develops from mesoderm.
Angiogenetic blood islands derv fr mesenchymal cells appear in the umbilical vesicle
and allantois during wk 3. Multiple blood islands eventually fuse into blood vessels
The outermost cells of the angioglenetic blood islands develop into the endothelial
lining of blood vessels, while the innermost cells become hematopoietic cells and
eventually blood.
Heart tube formation
•
•
•
•
Cardiogenic area located cranial to the buccopharyngeal membrane, this develops into
the heart and great vessels
Paired endocardial heart tubes develop during the third week and fuse to form a
single primordial heart tube
Heart tube joins up with the blood vessels in the embryo, connecting stalk, chorion,
and umbilical vesicle to form a primordial cardiovascular system; the heart begins to
beat on the 21st and 22nd day.
Gas and nutrient exchange between fetal and maternal circulations occur through the
development of blood vessels in chorionic villi covering the surface of the chorionic sac.
Cephalocaudal & lateral folding
•
•
•
•
Sides of embryonic disc grows faster than growth in long axis
“Wrap around” cephalocaudal folding occurs simultaneous to lateral folding
Amniotic cavity enlarges, yolk sac gets smaller.
Septum transversum & primordial heart move onto the ventral surface of the embryo
!
NIGEL FONG 2011/2012
PAGE A10
M1 NOTES IN GROSS ANATOMY
1 | EARLY EMBRYOLOGY
!
!
Formation of gut tube
•
Endodermal layer forms gut tube: foregut, midgut, hindgut
- Midgut communicates with yolk sac through vitelline duct
•
Allantois partially incorporated into body of embryo,
forming cloaca
Endoderm later gives rise to:
- Epithelial lining of resp sys
- Parenchyma of thyroid, parathyroid, liver, pancreas
- Reticular stroma of tonsils, thymus
- Epithelial lining of bladder & urethra
- Epithelial lining of tympanic cavity & auditory tube
•
!
!
Subsequent development
•
•
•
•
Week 4-8: Organogenesis of all other organs (except heart & CNS)
Development results from genetic plans and tissue interactions
Fetal period from Week 9 – birth is characterized mainly by growth.
Length of fetus usually indicated as crown-rump length (from tip of skull to base of
buttocks)
NIGEL FONG 2011/2012
PAGE A11
M1 NOTES IN GROSS ANATOMY
1 | EARLY EMBRYOLOGY
4. FETAL CIRCULATION & MEMBRANES
Development of the placenta
•
•
!
Maternal part: formed by decidua basalis, which forms from the endometrium
Formation of lacunar / intervillous spaces btw the chorionic & decidual plate
-
•
Erosion of materal spiral arteries in uterus transforms vessels fr small-diameter
high-resistance into larger-diameter low-resistance vessels for greater blood supply.
- Via cytotrophoblastic cells replacing maternal endothelial cells to form a hybrid of
fetal & maternal cells
- Blood released into lacunar / intervillous spaces
Fetal trophoblast forms villious chorion, ext into the lacunar (intervillous spaces)
-
•
initially has 4 layers: endothelium, connective tissue (from extraembryonic
mesoderm), cytotrophoblast and syncytiotrophoblast (syncytium)
- By week 20, middle 2 layers thin out to leave just the endothelium and some
syncytium separating fetal blood from maternal blood in the sinusoids
- Syncytial knots are aggregations of syncytiotrophoblastic nuclei that have broken
off and may be carried into the maternal circulation.
Development of blood supply complete by end of 1st trimester (12-13 wks)
Final placenta
•
•
•
•
Discoid structure, 15-20cm diameter, 500g weight
Placental membrane separates blood (mixing might result in immune reaction)
- Fetal blood in villi (capillaries)
- Maternal blood in sinusoids (intervillous spaces), bathing villi in blood
4th/5th month: Decidua forms decidual septa, projecting into intervillous spaces but do
not reach chorionic plate.
- Divides placenta into compartments: 15-20 cotyledons
Maternal side of placenta has characteristic cobblestone appearance due to cotyledons,
while fetal side is smooth.
- Upon delivery, it is important to check that the placenta is complete as retention of
a cortyledon in the uterus can cause severe uterine hemorrhage
NIGEL FONG 2011/2012
PAGE A12
M1 NOTES IN GROSS ANATOMY
1 | EARLY EMBRYOLOGY
Fetal circulation
•
•
•
Circulate to the yolk sac: Vitelline arteries & veins
- Yolk sac is a less significant source of nutrition in humans than in e.g. birds
Circulate to placenta: 2 Umbilical arteries & 1 umbilical vein
- Umbilical arteries arise from int iliac arteries (deoxygenated blood)
- Umbilical vein drains into inf vena cava (oxygenated blood)
- Initially 2 umbilical veins develop but only the left remains
Blood returning from the umbilical vein travels into the ductus venosus (bypass
liver), inferior vena cava, right atrium, and bypasses the uninflated pulmonary
circulation by being
- Shunted from right atrium to left atrium via foramen ovale
-
•
Enters the right ventricle, pulmonary trunk, and is shunted to the aorta through
the ductus arteriosus
The umbilical cord is eccentrically attached to the placents
-
Length ave 55-60cm. If too short, may restrict fetal movements; if too long, may
coil around neck/body of fetus
Fates of fetal vessels
•
Right-to-left shunts close
- Ductus arteriosus closes and becomes ligamentum arteriosum
-
•
Foramen ovale closes and becomes oval fossa
Umbilical vessels close
- Umbilical arteries become the medial umbilical ligaments (note: urachus forms
the median umbilical ligament
- Umbilical vein becomes the ligamentum teres (round ligament)
-
Ductus venosus becomes ligamentum venosus
!
The foetal circulation
arch of aorta
superior vena cava
ductus arteriosus
The ductus arteriosus and
foramen ovale allow blood
to bypass the lungs.
foramen ovale
pulmonary trunk
lung
pulmonary veins
left atrium
right atrium
inferior vena cava
descending aorta
right hepatic vein
Oxygenated blood flows
through 3 shunts, the:Ductus venosus,
Foramen ovale, and
Ductus arteriosus.
ductus venosus
The ductus venosus allows
blood to bypass the liver.
left hepatic vein
sphincter
portal
sinus
portal vein
umbilical vein
placenta
gut
Oxygen saturation of blood
kidney
High
Medium
umbilicus
Low
umbilical
arteries
urinary bladder
superior vesical artery
internal iliac artery
external iliac artery
lower limbs
NIGEL FONG 2011/2012
PAGE A13
M1 NOTES IN GROSS ANATOMY
1 | EARLY EMBRYOLOGY
Amnion
•
•
•
•
•
When first formed (see cephalocaudal / lateral folding), in
contact with body of embryo.
Amniotic fluid begins to accumulate in week 4-5
As the amnion expands and ultimately adheres to the inner
surface of the coleum, the chorionic (extraembryonic) cavity
is obliterated
Function: absorbs jolts, prevents adherence of embryo to
amnion, allow for fetal movement
Fetal urine added to amniotic fluid, which is then
swallowed by the fetus (mainly water as placenta is
functioning as exchange for metabolic wastes)
NIGEL FONG 2011/2012
!
PAGE A14
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
CHAPTER 2: NORMAL STRUCTURE AND DEVELOPMENT OF THE
2 | UPPER LIMBS
!
!
1. BONES, REGIONS & MUSCLE ATTACHMENTS
Principle: Bones form an outward projection (known alternately as tuberosity/tubercle/trochanter etc) at the
attachment of muscles and ligaments. This strengthens the bone at the point where the muscles pull on them.
A. CLAVICLE
!
Bone
•
•
•
•
•
•
Enlarged sternal (med) end articulates w manubrium of sternum at sternoclavicular jt
Flat acromial (lat) end articulates w acromion of scapula at acromioclavicular jt
Medial 2/3 convex anteriorly, lateral 1/3 concave anteriorly.
Superior surface smoother than inferior surface
Serves as a moveable strut from which the scapula and free limb are suspended.
First long bone to ossify and does so by intramembranous ossification: has no marrow
cavity.
Muscle attachments
1
2
3
-
Trapezius
Deltoid
Subclavius
Sternocleidomastoid
Ligaments
L1
L2
Conoid (med. coracoclavicular)
Acromioclavicular (lat coracoclavicular)
L3
L4
Sternoclavicular
Costoclavicular
Clinical notes
•
•
Tends to fracture at the point where the curvature changes
Patients with clavicular fracture often supporting their injured upper limb with the
other upper limb
!
NIGEL FONG 2011/2012
PAGE A15
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
B. SCAPULA
!
Bone
Ligaments
L1
L2
L5
L7
L8
Conoid (med. coracoclavicular)
Acromioclavicular (lat coracoclavicular)
Glenohumeral lig
Coracohumeral lig
Coracoacromial lig
Muscle attachments
5
6
7
8L
9L
10
11
Levator scapulae
Rhomboid min
Rhomboid maj
Triceps brachii (long h)
Biceps brachii (long h)
Teres min
Teres maj
12
13
14
15
9S
16
17
Supraspinatus
Infraspinatus
Subscapularis
Seratus anterior
Biceps brachii (short h)
Pectoralis min
Coracobrachialis
Movements of shoulder girdle
•
•
Shoulder girdle = scapula + clavicle
Shoulder girdle can move on top of the thoracic wall and contributes significantly to
the mobility of the upper limb
!
NIGEL FONG 2011/2012
PAGE A16
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
C. HUMERUS
Bone
Muscle attachments
8T
8M
9L
Triceps (lat h)
Triceps (med h)
Tendon of biceps (long h)
passes through bicipital groove
Teres maj
Latissimus dorsi
Pectoralis maj
11
4
19
10
12
13
14
18
20
21
Teres min
Supraspinatus Rotator cuff
muscles
Teres min
Subscapularis
Brachialis
Brachioradialis
Ext carpi radialis longus
22
23
24
Common extensor origin
(all sup. forearm extensors ex.
brachiorad, ex carpi rad long)
Common flexor origin
(all sup. forearm flexors)
Anconeus
Clinical notes
•
•
Surgical neck is the weakest point of the bone and is commonly fractured. As the
surgical neck is in direct contact with the axillary nerve and ant & pos circumflex
artery, surgical neck fractures endanger these structures
Radial groove is in direct contact with the radial nerve, the distal humerus with the
median nerve, and the medial epicondyle with the ulnar nerve. Fractures may endanger
these structures
NIGEL FONG 2011/2012
PAGE A17
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
Arm region
•
Compartments of arm: Anterior (flexor), Posterior (extensor)
D. RADIUS & ULNA
Bone
•
•
•
•
•
•
•
Ulna is larger proximally, radius is larger distally
Humeroulnar joint: Radius articulates with capitulum of humerus as the radial head
fits into the radial fossa of the humerus, Ulna articulates with trochlea of humerus as
the olecranon fits into the olecranon fossa and coronoid process fits into the coronoid
fossa of the humerus
Radius can pivot about the radial notch of ulna in supination and pronation
Only the radius articulates with the carpal bones
Ulnar styloid process is smaller than the radial styloid process, so more adduction is
possible than abduction
Interosseous membrane between radius and ulna run obliquely, passing inferiorly from
the radius into the ulna, so as best to transmit forces received from the hands by the
radius to the ulna
Transmission of force: Metacarpals - Carpals – Radius – Interosseous membrane – Ulna
– Humerus – Scapula – Clavicle – Thorax
NIGEL FONG 2011/2012
PAGE A18
M1 NOTES IN GROSS ANATOMY
Muscle attachments
8
9
18
20
24
Triceps brachii
Biceps brachii
Brachialis
Brachoioradialis
Anconeus
2 | UPPER LIMBS
25
26
27
28
29
Flexor digitorum superficialis
Pronator teres
Flexor pollicis longus
Flexor digitorum profundus
Pronator quadratus
30
31
32
33
54
Supinator
Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus
Extensor indicis
!
Clinical notes
•
Radius and ulna are tightly bound, so a fracture of one is likely to lead to a dislocation
of the other.
Forearm region
•
Compartments of arm: Anterior (flexor), Posterior (extensor)
NIGEL FONG 2011/2012
PAGE A19
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
E. HAND
Bones
•
•
Hamate has a hook
Pisiform is a sesamoid bone in the tendon of flexor carpi ulnaris
Muscle attachments (anterior surface)
23U
Flexor carpi ulnaris
34
Abductor pollicis brevis
23R
Flexor carpi radialis
35
Opponens pollicis
39
Adductor pollicis
36
Flexor pollicis brevis
40
Flexor pollicis longus
43
Flx digitorum profundus
41
Abductor digiti minimi
44
Flx digitorum superficialis
40
Opponens digiti minimi
45
Palmar interossi
42
Flexor digiti minimi
Muscle attachments (posterior surface)
46
Extensor carpi ulnaris
49
Extensor digitorum
47
Extensor carpi radialis longus
54
Extensor pollicis indicis
48
Extensor carpi radialis brevis
55
Extensor pollicis longus
50-53
Dorsal interossi
56
Extensor pollicis brevis
Clinical notes
•
•
Thenar eminence
Hypothenar
eminence
Not shown: Lumbricals (4)
Scaphoid fractures: The scaphoid is the most commonly fractured carpal bone and
avascular necrosis of the proximal fragment, which has poor blood supply, may result.
Fractures are easy to miss on radiographs – do ask for ‘scaphoid view’.
Falls on outstretched hand also tends to cause dislocation of the lunate
NIGEL FONG 2011/2012
PAGE A20
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
2. JOINTS OF THE UPPER LIMBS
movements of joints are covered under muscles
A. GLENOHUMERAL JOINT
!
Articulation
Distally: rounded humeral head
Proximally: shallow, pear-shaped glenoid cavity of the scapula, which is deepend by the
glenoid labrum
•
•
Cartilage
Articular surfaces covered by hyaline cartilage
•
Type
•
Synovial ball & socket joint
Synovial membrane
•
•
•
•
Lines capsule, attached to margins of articular surfaces
Produces viscous synovial fluid to lubricate joint
Tubular sheath surrounds the tendon of the long head of biceps brachii as it descends
through the bicipital groove
Synovial membrane extends through the anterior capsule wall, forming the
subscapularis bursa beneath the subscapularis.
Capsule
•
•
•
Fibrous capsule encloses the joint and
is attached the the margin of the
glenoid labrum on the scapula, and the
anatomical neck of the humerus
Inferior aspect is weak and lax, having
enough slack to accomodate abduction
Strengthed by fibrous slips from rotator
cuff muscles
Ligaments
LIGAM.
LOC
SCAPULAR ATT
GLENOID ATT
Glenohumeral
(sup, med, inf)
Ant
Glenoid labrum at
supraglenoid tubercle
Anatomical neck
Coracohumeral
Ant
Coracoid process
Ant. greater tubercle
Coracoacromial
Sup
Coracoid process
Acromion
Prev sup displacement
Transverse hum.
Dist
Greater tubercle
Lesser tubercle
Hold biceps tendon
NIGEL FONG 2011/2012
FUNCTION
Reinforcement
PAGE A21
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
Blood supply
•
•
Ant & Pos circumflex humeral arteries
Branches of suprascapular artery
Nerve supply
•
•
Axillary
Suprascapular
Stability
•
•
•
Stability is sacrificed to permit a wide range of movement
Stability depends on tone on the rotator cuff muscles to hold the humerus in the
glenoid fossa.
Joint is weakest inferiorly, where the rotator cuff is deficient.
Clinical notes
•
•
Inferior dislocation: Most glenohumeral dislocations are anterior-inferior, due to the
strong coraco-acromial arch and rotator cuff superiorly, but its deficiency inferiorly.
The glenohumeral joint is most vulnerable to dislocation when abducted.
Frozen shoulder (adhesive capsulitis): Adhesive fibrosis and scarring of the joint
capsule, rotator cuff, and deltoid results in difficulty in abducting arm (except via
scapular rotation). The supraspinatus tendon is particularly vulnerable to calcification
due to poor blood supply
!
NIGEL FONG 2011/2012
PAGE A22
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
B. HUMEROULNAR (ELBOW) & PROXIMAL RADIOULNAR JOINT
!
Articulation
Humeroulnar joint: Btw pulley-shaped trochea & trochlea notch of ulnar, capitulum of
humerus & head of radius. Wrench-shaped olecranon prevents hyperextension.
Proximal radioulnar joint: Btw head of radius and radial notch of ulna
•
•
Cartilage
Articular surfaces covered by hyaline cartilage
•
Type
•
•
Humeroulnar joint: Synovial hinge joint
Proximal radioulnar joint: Synovial pivot joint
Synovial membrane
•
•
•
•
•
Lines capsule, attached to margins of articular surfaces
Produces viscous synovial fluid to lubricate joint
Synovial cavity of the two joints are continous
Synovial mem covers fatty pads in the floor of the coronoid, radial, and olecranon
fossa, which accommodate the bony processes during flexion & extension of the elbow
Sacciform recess of synovial membrane protrudes from inferior free margin of the joint
capsule to facilitate rotation of the radial head during pronation and supination
Capsule
•
•
Capsules of both joints are continous
Attached to margins of fossas, in front of epicondyles, margin of coronoid process and
anular ligament
Ligaments
LIGAM.
LOC
SUPERIOR ATT
DISTAL ATT
Radial
Lat
Lat epicondyle
Anular lig.
Ulnar
Med
Med epicondyle
Coronoid, Olecranon
Anular lig of rad
Dist
Encircles head of radius
NIGEL FONG 2011/2012
FUNCTION & NOTES
(ant, pos, transv bands)
Pronation / supination
PAGE A23
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
Blood supply
•
Anastomosis around elbow joint derived from brachial, ulnar, and radial artery
Nerve supply
•
•
•
•
Musculocutaneous
Radial
Median
Ulnar
Clinical notes
•
•
•
Fracture of radial head: Common with a fall on the outstretched hand.
Radiologically, this fracture may not be visible. However, fluid filling the synovial
cavity may elevate the fatty pads, showing a “fat pad sign” i.e. area of lucency instead.
Epicondylitis: Overuse strain on the common flexor and extensor origins on the
epicondyles. In tennis players the pain occurs on common extensor origin at the the
lateral epicondyle (“tennis elbow”), while in golfers it occurs on the common flexor
origin at the medial epicondyle
Subluxation of radial head (pulled elbow): When children are suddenly lifted by
their upper limb while the forearm is pronated, the distal attachment of the anular
ligament may be torn.
C. RADIOCARPAL (WRIST) JOINT
!
Articulation
•
•
Proximally: Distal end of radius and articular disc of the distal radioulnar joint
(triangular ligament) which binds the ulnar and radial ends
Distally: Proximal carpal bones except the pisiform
Cartilage
•
Articular surfaces covered by hyaline cartilage
Type
•
Synovial ellipsoid / condyloid joint.
Synovial membrane
•
•
•
Lines capsule, attached to margins of articular surfaces
Produces viscous synovial fluid to lubricate joint
Does not communicate with the distal radioulnar joint and intercarpal joints.
Capsule
•
Surrounds wrist joint and attached to distal ends of radius, ulna, and proximal carpal
bones except the pisiform
NIGEL FONG 2011/2012
PAGE A24
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
Ligaments
LIGAM.
LOC
SUPERIOR ATT
DISTAL ATT
Palmar
Ant
Radius
Carpals
Dorsal
Pos
Radius
Carpals
Ulnar collateral
Med
Ulnar styloid process
Triquetrium
Radial collateral
Lat
Radial styloid process
Scaphoid
FUNCTION
Stabilization
Blood supply
•
Dorsal & palmar carpal arches
Nerve supply
•
•
•
Median
Radial
Ulnar
D. OTHER JOINTS
JOINT
TYPE
LIGAMENTS & CAPSULE
MOVEMENTS
NOTES
Sternoclavicular
Saddle
Ant & pos sternoclavicular,
Interclavicular, Costoclavicular
Articular disc
Protract & retract
Elevate & depress
Strong
Acromioclavicular
Plane
Acromioclavicular
Coracoclavicular: conoid &
trapezoid
Gliding
Distal radioulnar
Pivot
Articular disc (see C)
Pronate & Supinate
Plane
Common articular cavity
Palmar lig btw carpometac 2-5
Limited
Carpometacarpal 1
Saddle
Separate cavity
Fx/Ext, Ab/Ad/Op
Metacarpophalangeal
Condyloid
Palmar aponeurosis
Fx/Ext, Ab/Ad
Interphalangeal
Hinge
Intercarpal
Carpometacarpal 2-5
NIGEL FONG 2011/2012
Unique fr 2-5
Fx/Ext
PAGE A25
M1 NOTES IN GROSS ANATOMY
Anterior
19
Pectoralis maj
NERVE
2 | UPPER LIMBS
ORIGIN
INSERTION
ACTION ON
SCAP/C
ARM
Ad, MedR
[sternocostal h]
Lat &
med
pectoral n
16
Pectoralis min
Med pect
Ribs 3-5
Scapula: coracoid proc
Depress
Retract
3
Subclavius
N to
subclavius
1st rib
1st costal cartilage
Clavicle: inf mid 1/3
Depress
15
Serratus ant
Long
thoracic
Ribs 1-8:
ext surf of lat part
Scapula:
ant med border
Protract
SupRot
[clavicular h]
Clavicle: ant med 1/2
Sternum, costal
cartilage 1-6
Humerus: lat lip,
intertubercular sulcus
-
Fx if ext
Ext if fx
!
!
!
!
Clinical notes
•
Winged scapula: Paralysis of serratus anterior due to injury to long thoracic nerve
gives a winged scapula – med. border of scapula moves laterally and posteriorly away
from the thoracic wall. Abduction of the upper limb above the horizontal may be
difficult as the serratus anterior is unable to completely rotate the scapula to allow
complete abduction. The long thoracic nerve is vulnerable to damage as it supplies the
serratus anterior from its superficial surface (most nerves supply from deep surface)
!
!
NIGEL FONG 2011/2012
PAGE A27
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
B. SCAPULOHUMERAL (INTRINSIC SHOULDER) MUSCLES
!
MUSCLE
2
ORIGIN
INSERTION
Axillary n
Clavicle: lat 1/3
Scapula: spine, acromion
Humerus: deltoid
tuberosity
Scapula: subscapular fossa
Humerus:
lesser tubercle
Deltoid
[ant fibres]
ACTION
ON ARM
NERVE
[post fibres]
Abd 15º+
Fx, MedR
Ex, LatR
Rotator cuff:
14
Subscapularis
12
Supraspinatus
13
Upper/lower
subscapular
Scapula: supraspinous fossa
Infraspinatus
Suprascapular
10
Teres min
Axillary n
Scapula: lat border, mid part
11
Teres maj
Lower
subscapular
Scapula: inf angle, pos surf
Scapula: infraspinous fossa
Humerus:
greater
tubercle
Sup. facet
Mid facet
Inf facet
Humerus: medial lip,
intertubercular sulcus
MedR
Abd 0-15º
LatR
Add,
MedR
!
!
!
Clinical notes
•
•
•
Supraspinatus is responsible for initiating the first 15º of abduction, after which the
detoid takes over. With a dysfunctional supraspinatus, the arm can still be abducted
by tilting the body to allow the hand to passively abduct to 15º, before the deltoid
takes over.
Scapulo-humeral mechanism: For every 3º of abduction of the arm, a 2º abduction
occurs in the shoulder joint and 1º occurs by rotation of the scapula. At about 120º of
abduction, the greater tuberosity of the humerus comes into contact with the lateral
edge of the acromion. Further elevation of the arm above the head is accomplished by
rotating the scapula
Rotator cuff muscles: The supraspinatus, infraspinatus, teres minor, and
subscapularis are responsible for stabilizing the glenohumeral joint, holding the large
humeral head in the shallow glenoid cavity. Inflammation of the rotator cuff or
calcification of the supraspinatus tendon is a common cause of shoulder pain.
!
NIGEL FONG 2011/2012
PAGE A28
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
C. ARM MUSCLES
!
Anterior
9
NERVE
Biceps brachii
ORIGIN
Scapula:
[long h]
Musculocutaneous
[short h]
17
Coracobrachialis
18
Brachialis
ACTION ON
INSERTION
Supraglenoid tubercle
Coracoid process
Humerus: ant surf
SHLDER
HUM
RAD/UL
Radial
tuberosity
Flex
Flex
Supinate
-
Flex
Hum: midshaft
Flex
Ulnar tuberos.
-
-
-
Flex
-
!
Posterior
8
NERVE
Triceps brachii [long h]
[lat h]
[med h]
ORIGIN
INSERTION
ACTION ON
SHLDER
HUM
Ext
Ext
Scapula: infraglenoid tubercle
Radial
Hum:
pos surf
Sup to radial
groove
Ulna:
olecranon
Inf to radial groove
Clinical notes
•
•
•
•
•
Biceps tendon reflex (tapping on the biceps tendon at the cubital fossa) tests for
integrity of the C5/C6 spinal segments and the musculocutaneous nerve.
Triceps tendon reflex (on the triceps tendon at the olecranon) tests for integrity of
C6-C8 (esp. C7) and the radial nerve
Musculocutaneous nerve pierces the coracobrachialis.
Brachioradialis (in pos forearm) works to flex the forearm when mid-pronated
Tendon of long head of biceps is enclosed in a synovial sheath and moves back and
forth in the intertubercular sulcus (bicipital groove) between the greater and lesser
tuberosities of the humerus. Wear and tear can cause shoulder pain and inflamation.
NIGEL FONG 2011/2012
PAGE A29
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
D. FOREARM MUSCLES
!
Anterior
NERVE
ORIGIN
INS
Ulnar
Olecranon
Via pisohamate lig
to hamat hook &
metacarp 5
ACTION ON
RAD/UL
WRIST
FING.
Superficial layer:
23U
Flx carpi ulnaris
[ulnar h]
[humeral h]
Palmaris longus
23R
Flx. carpi radialis
26
Pronator teres
Hum: med
epicondyle
Intemediate layer:
25
Flx digitorum sup.
[humeral h]
-
Palmar aponeurosis
Flex
Metacarp 2
Flx Ab
Rad: lat midshaft
Median
[ulnar h]
Flx Ad
Pronate
Flex
mid p
2-5
Mid. phalanges 2-5
Coronoid p
Deep layer:
28
Flx digitorum prof.
27
Flx pollicis longus
29
Pronator quadratus
-
-
Dist. phalanges 2-5
Ulnar
Ulna: prox
ant surf &
interos mem
Flex
p 2-5
Median
Rad: ant surf
interos mem
Dist. phalanx 1
Flex
p1
[lat 1/2]
[med 1/2]
-
Dist. ant surf of radius & ulna
Pronate
-
!
!
NIGEL FONG 2011/2012
PAGE A30
M1 NOTES IN GROSS ANATOMY
Posterior
NERV
2 | UPPER LIMBS
ORIGIN
INS
Hum: Lat. supraepicondylar ridge
Rad: lat dist
ACTION ON
RA/UL
WRIST
FING.
Superficial layer:
20
Brachioradialis
47
Ext carpi rad longus
48
Ext carpi rad brevis
Metacarp 3
49
Ext digitorum
Ext. hood 2-5
Ext digiti minimi
Ext hood 5
46
Ext carpi ulnaris
24
Anconeus
Deep layer:
30
Humerus: lat.
epicondyle
Flex
Metacarp 2
-
Ex, Ab
-
Metacarp 5
Olecranon
-
-
Ex 2-5
Ex 5
Ex, Ad
Abd.
Radial
-
Supinator
[humeral h]
[ulnar h]
Ulna: Supinator crest
Rad: lat surf
prox 1/3
31
Abd pollicis longus
Ulna: pos prox 1/2
Metacarp 1
32
Ext pollicis longus
Ulna: pos mid 1/3
Dist phalx 1
33
Ext pollicis brevis
Radius: pos dist 1/3
Prox phalx 1
34
Ext indicis
Ulna: pos dist 1/3
Ext hood 2
Supin.
Ab/Ex 1
-
Ex
Ex 2
!
!
NIGEL FONG 2011/2012
PAGE A31
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
Pronation & Supination
The most powerful supinator (especially when the arm is flexed) is the biceps brachii.
!
Movements of the wrist
Combinations of movements of the flexor/extensor carpi ulnaris/radialis muscles work together
to generate movements of the wrist.
Clinical notes
•
•
!
Palmaris longus is absent in 15% of people
The flexor retinaculum holds the tendons of flexor muscles in place, preventing
bowstringing, while the extensor retinaculum holds that of the extensor muscles.
NIGEL FONG 2011/2012
PAGE A32
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
E. INTRINSIC HAND MUSCLES
!
MUSCLE
NERVE
ORIGIN
INS
ACTION
Thenar eminence
34
Abd pollicis brevis
36
Flx pollicis brevis
35
Opponens pollicis
Median
Ab 1
Flexor retinaculum,
scaphoid/trapezium
tubercles
Prox phalanx 1: lat
Metacarpal 1: lat
Opp 1
Tendon of flexor
digitorum profund.
Ext hood 2-3
Fx metacar,
Ex interphlx
Prox phlx
, ext hood
Fx 1
Hand muscles
Lumbrical
1/2 (lat)
3/4 (med)
50-53
Dorsal interossi
Adjacent metacarp.
3x 45
Palmar interossi
Metacarp 2, 4, 5
Adductor pollicis*
Capitate & adjs
Metacarp 3
39
Ulnar
Ext hood 4-5
2, 3, 3, 4
Ab 2, 3, 3, 4
2, 4, 5
Ad 2, 4, 5
Prox phalanx 1: med
Ad 1
Hypothenar eminence
41
Abd digiti minimi
Pisiform
42
Flx digiti minimi brevis
40
Opponens digiti minimi
Flexor retinaculum,
hook of hamate
Prox phalanx 5: med
Metacarp 5: med
Ab 5
Fx 5
Opp 5
*The adductor pollicis is sometimes considered to be a thenar muscle, even though it does not really contribute to the
thenar eminence
NIGEL FONG 2011/2012
PAGE A33
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
!
Fine movements of the hands
•
•
•
Abduction of the fingers is defined with respect to the middle finger. The middle finger
has two dorsal interossi (to abduct to either side) but no palmar interossi (adduction is
fulfilled by the opposite dorsal interossi)
The thumb is the most important digit and opposition of the thumb is crucial in
gripping. Its axis is rotated 90º wrt the other fingers so that it can be brought into
contact with the palm and pads of other fingers.
The lumbricals and interossei are important in precision hand movements, e.g. in the
upstroke when writing ‘t’
!
NIGEL FONG 2011/2012
PAGE A34
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
4. NERVES OF THE UPPER LIMB
Principle: nerves & vessels tend to travel together in neurovascular bundles. Nerves exhibit the least
anatomical variations, veins the most. Nerves usually supply muscles from their deep surface, except the
serratus anterior.
!
A. BRACHIAL PLEXUS
!
Formation
•
•
Somatic plexus formed from the anterior rami of C5-C8 & T1.
Anatomical variation: prefixed brachial plexus includes C4 contributions, postfixed
brachial plexus includes T2 contributions
!
Organization
•
•
•
•
•
•
Roots are the anterior rami of C5-C8
Roots merge into superior (C5-6), middle (C7) and inferior (C8-T1) trunks
Trunks divide into anterior and posterior divisions
Anterior divisions of the superior and middle trunks unite to form the lateral cord,
while that of the inferior trunk continues as the medial cord.
Posterior divisions of all trunks unite as the posterior cord.
Identification of the lateral & medial cord, and its division into musculocutaneous,
median, and ulnar nerves is assisted by looking for the ‘M’ formed.
NIGEL FONG 2011/2012
PAGE A35
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
Branches of the brachial plexus
NERVE
ORIGIN
COURSE
INNERVATION
Dorsal scapula
Root, C5
Pierces middle scalene
Scapula: med border (w artery)
Rhomboids
Long thoracic
Root, C5-C7
Axilla: med wall
Serratus ant.
Scapular notch (w artery)
Supra/infraspinatus
Suprascapular
N to subclavius
Trunk, sup.
Subclavius
Sup. subscapular
Inf subscapular
Subscapularis
Cord, pos
Thoracodorsal
Lat. pectoral
Cord, lat
Med pectoral
Med cutan. n of arm
Med cutan. n of forearm
NIGEL FONG 2011/2012
Subscapularis, Teres maj
Axilla: pos wall
Latissimus dorsi
Name follows origin. Lat
pectoral n is the medial one.
Pectoralis maj
Cord, med
Pectoralis min
Skin: med arm
With ulnar n then basilic vein
Skin: med forearm
PAGE A36
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
Clinical notes
•
Waiter’s tip position (Erb’s palsy): Superior parts of the brachial plexus may be
injured from an increase in the angle between the neck and shoulder, e.g. being thrown
from a motorcycle and landing on the shoulder, or excessive stretching of the neck
during delivery. As a result, the adducted limb hangs by the side in medial rotation
and extension of elbow.
B. MAJOR UPPER LIMB NERVES
ORIGIN
COURSE
TERM
BRANCH
SS
Motor
Sensory
CLINICAL
!
Axillary Nerve
Musculocutaneous Nerve
Brachial plexus: pos cord
Brachial plexus: lat cord
Enter quadrangular space
Pierces coracobrachialis (identification key)
Descend btw biceps brachii and brachialis
• With circumflexhumeral pos hum art
Winds round surgical neck of humerus
deep to deltoid
Pierces deep fascia above elbow to cont as
lat cutaneous n of forearm
Articular branches to shoulder joint
Articular branches to elbow
Superior lateral cutaneous n of arm
Muscular branch to arm flexors
Deltoid, teres min.
Ant arm flexors
Skin over inferior part of deltoid
Shoulder jt
Skin of lat forearm
Elbow jt
Important not to injure when giving
intramuscular injections into the deltoid
NIGEL FONG 2011/2012
PAGE A37
M1 NOTES IN GROSS ANATOMY
!
2 | UPPER LIMBS
Sensory supply of hand
ULNAR!
!
MEDIAN!
RADIAL!
PALM!
!
!
!
DORSAL!
!
!
!
Radial nerve
ORIGIN
COURSE
TERM
BRANCH
!
Brachial plexus: pos. cord
• Exits thru triangular interval btw lat. margin
of long head of triceps, humeral shaft, and
inf. margin of teres maj
• Runs in spinal (radial) groove of humerus w
profunda brachii artery
• Pierces intermuscular septum
• Cont in ant compartment of arm
• Passes ant. to lat epicondyle
• Divide into deep and superficial branches
Deep branch (motor)
Wind lat around radius (pierce supinator)
Run in & supply pos forearm muscles
Superficial branch (cutaneous)
Wind lat around radius (pierce supinator)
Cont to hand, crossing anatomical snuffbox
Articular branches: elbow joint
Muscular branches: to all muscles supplied
Cutaneous: Pos. cut nerve of arm, lower lat. cut nerve of arm, pos. cut nerve of forearm
SS
Motor
Sensory
CLINICAL
All muscles in pos. compartment of arm & forearm
Skin of posterior and inferolat arm, post. arm
Skin of dorsum of hand
Injury e.g. due to humeral shaft fracture, pressure in axilla region (badly fitting crutch)
• Wrist drop: inability to ext wrist & fingers; unable to flex strongly for power grip
• Loss of ext of elbow (if lesion is in the axilla)
• Loss of sensation to lat 2/3 of dorsum (note: cutaneous branches given off before the
neck of the radius, if lesion is at neck of radius this does not occur)
NIGEL FONG 2011/2012
PAGE A38
M1 NOTES IN GROSS ANATOMY
!
2 | UPPER LIMBS
Ulnar Nerve
ORIGIN
COURSE
TERM
BRANCH
Brachial plexus: medial cord
•
•
•
•
•
•
•
Runs medial to axillary artery
In middle of arm, penetrate intermuscular septum and enters pos compartment
Passes elbow post to med epicondyle
Ent ant compartment of forearm by passing between flexor carpi ulnaris heads
Descends behind flexor carpi ulnaris, medial to ulnar artery
At wrist, pass between tendon of flexor carpi ulnaris & flexor digitorum profundus
Enter hand sup to flx retinaculum, in Guyon’s canal btw pisiform and hamate hook
Divides into sup & deep terminal branches
Articular br: elbow joint
Muscular br: to flexor carpi ulnaris, med. flexor digitorum profundus
Cutaneous br: Palmar cut br to supply hypothenar, dorsal cut br to dorsum of hand
SS
Motor
Sensory
CLINICAL
Intrinsic hand muscles except thenar muscles and 2 lateral lumbricals
Flexor carpi ulnaris and med 1/2 of flexor digitorum profundus
Hand: medial 1.5 digits
Commonly injured at subcutaneous locations behind the medial epicondyle (e.g. with
fracture of epicondyle) and at the wrist (e.g. slashed wrist)
• Clawed hand (see below)
• Loss of sensation to medial 1/3 of palm & dorsum
• Atrophy of hypothenar eminence
Clawed hand:
• Check whether it is a partial (ulnar/median) claw or complete claw
• Ulnar claw: hyperextension of 4th-5th digit at metacarpophalangeal joints and
hyperflexion at interphalangeal joints due to atrophy of interossei and lumbricals but
unopposed action of extensors and flexor digitorum profundus
• Ulnar paradox: The higher the lesion, the less obvious the clawing deformity. In
wrist lesions, flexor digitorum produndus is not paralyzed, causing marked flexion of
terminal phalanges. But in higher lesions, FDP paralysis decreases flexion of terminal
phalanges, making the claw less obvious
Guyon/Ulnar canal syndrome: compression of ulnar nerve at Guyon’s canal, leading
to weakness of hand muscles and hyposthesia in medial 1.5 fingers
NIGEL FONG 2011/2012
PAGE A39
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
Median Nerve
ORIGIN
COURSE
TERM
BRANCH
Medial root: from medial cord of brachial plexus
Lateral root: from lateral cord of brachial plexus
•
•
•
•
Runs lat to brachial artery, before crossing over to med side
Run through cubital fossa below bicipital aponeurosis, med to brachial art.
Enter forearm btw heads of pronator teres
Cont. btw flexor digitorum sup & prof
At wrist – behind palmaris longus tendon
Pass through carpal tunnel deep to flexor retinaculum
Articular br: elbow joint
Muscular br: to ant forearm muscles
Ant interosseous n: to flexor pollicis longus, lat flexor digitorum profundus, wrist jt
Palmar cutaneous br: to lateral part of palm
SS
Motor
Sensory
CLINICAL
All forearm ant muscles except flexor carpi ulnaris & med 1/2 of flexor digitorum prof
Hand: Thenar muscles, first 2 lumbricals
Hand: lat 3.5 digits
Carpal tunnel syndrome (see carpal tunnel)
In wrist slash injury
•
•
•
•
Loss of sensation of lat 3.5 digits
Paralysis and wasting of the thenar muscles and 1st 2 lumbricals
Opposition of the thumb and fine control of 2nd & 3rd digits is not possible.
Ape-like hand: thumb laterally rotated and adducted
Supracondylar fracture or other damage to the median nerve at the elbow region also
results in (in addition to signs due to injury at wrist)
• Benediction sign: Loss of flexion at interphalangeal joints of 2nd and 3rd digits
• Loss of flexion of wrist
• Forearm kept in supine position as pronator muscles paralysed
!
!
NIGEL FONG 2011/2012
PAGE A40
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
Overview of ant forearm
!
Dermatomes & Myotomes of upper limb
•
•
•
•
!
Based on C5-T1 of brachial plexus
Dermatomes (right): start from shoulder, lateral
side, go round fingers, medial side, axilla.
Myotomes: segmental pattern proximal to distal
(instead of lateral to medial)
- Shoulder abduction: C5
- Flexors of forearm: C5-6
- Extensors of forearm: C6-8 (esp C7)
- Muscles in forearm: C7-8
- Intrinsic muscles of hand: T1
Clinical: Lesion of nerve root – e.g. T1 motor root
lesion results in claw hand without sensory loss.
Distinguish from ulnar claw
!
!
NIGEL FONG 2011/2012
!
PAGE A41
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
5. BLOOD SUPPLY OF THE UPPER LIMB
A. ARTERIAL SUPPLY
!
Axillary Artery
ORIGIN
COURSE
TERM
BRANCH
Continuation of subclavian art at lat border of first rib
1st part: From lat border of first rib to med border pectoralis min
2nd part: Deep to pectoralis min
3rd part: From lat border pectoralis min to inf border of teres maj
Continues as brachial art at inf border of teres maj
1st part:
Sup. thoracic art
Small, upper med & ant axillary wall
2
Thoraco-acromial
Pierces clavipectoral fascia, divide into pectoral,
deltoid, acromial, and clavicular branches
Lat thoracic
Axillary border of pec min, onto thoracic wall
Subscapular
Large, gives:
Circumflex scapular art: pass through
triangular sp. to supply dorsum of scapula
Thoracodorsal art: on lat border of scapula
Ant circumflex hum art
Smaller
Pos circumflex hum art
Quad space, then
nd
part:
3 part:
rd
CLINICAL
Encircle surgical neck of
humerus
Anastomoses: important scapular anastomosis between subclavian & axillary artery
allows bypass of 2nd part of axillary artery, ensuring adequate blood flow regardless of the
position of the arm. However, the anastomosis is deficient between the subscapular
artery and profunda brachii artery, and sudden occlusion does not allow sufficient time
for adequate collateral circulation to develop.
*Branches of the axillary artery: “Some Times Life is Such A Pain”
NIGEL FONG 2011/2012
PAGE A42
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
Brachial Artery
ORIGIN
COURSE
TERM
Continuation of axillary artery inferior
to inf border of teres maj
Medial side of prox arm
• With median nerve & brachial vein
Passes through cubital fossa
• med to biceps tendon, lat to median
nerve
Divides into ulnar and radial arteries
BRANCH
Profunda brachii art: accompanies
radial nerve in radial (spiral) groove
Muscular branches to muscles
Nutrient artery to humerus
Collateral arteries to elbow anastomosis
CLINICAL
Brachial pulse can be felt halfway on the
med arm between the biceps and triceps.
Compression of the brachial artery here
is used to measure blood pressure.
!
ORIGIN
COURSE
TERM
BRANCH
Radial artery
!
Ulnar Artery
Terminal branches of brachial artery in cubital fossa (ulnar is larger)
Deep to brachioradialis
Pos forearm, resting on deep muscles
• Lat to ulnar nerve
Lat to flx carpi radialis
Dist forearm: becomes superficial
Wind round lat. radius
Wrist: btw flx carpi ulnaris & flx dig sup
Cross floor of anatomic snuffbox
Sup to flx retinaculum
Guyon’s canal btw pisiform & hamate
Forms superficial & deep palmar arches, which then give branches to fingers
Recurrent branches to arterial anastomoses of elbow joint
Muscular branches
Muscular branches
Ant & pos interosseous art: on ant/pos
surf of interosseous mem.
CLINICAL
Radial pulse: wrist, lat to flx carpi radialis
NIGEL FONG 2011/2012
Ulnar pulse: wrist, lat to flx carpi ulnaris
PAGE A43
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
B. VEINOUS DRAINAGE
!
ORIGIN
COURSE
TERM
BRANCH
CLINICAL
!
Cephalic vein
Medial
Dorsal venous network of hand
Wind round lat border of forearm
Ascend in deltopectoral groove
• Btw deltoid & pec maj
Pierces deep fascia to drain into the
axillary vein in the clavipectoral triangle
Lateral
Wind round med border of forearm
Up front of arm on med. side of biceps
Pierces deep fascia to join venae
comitantes of the brachial artery
Bec. axillary vein at inf border teres maj.
Median cubital vein: highly variable branch of cephalic vein, drains into basilic vein
Lies on bicipital aponeurosis, sup. to brachial artery and median nerve
Median cubital vein is used for drawing blood, IV injections, and blood transfusions.
Care has to be taken not to puncture the bicipital aponeurosis, which may result in
injury to the brachial artery and median nerve
!
Deep Veins
•
•
Basilic vein
Deep veins accompany major arteries and their branches as paired venae comitantes.
Clinical: The vein punctured in a ‘subclavian vein puncture’ is the terminal part of the
axillary vein. At this point, the axillary vein is anteroinferior to axillary artery and
brachial plexus.
!
NIGEL FONG 2011/2012
!
PAGE A44
M1 NOTES IN GROSS ANATOMY
C. BREASTS
!
(geographically in thorax region, but clinically related to axilla)
Outer structure
•
•
•
•
•
•
!
2 | UPPER LIMBS
The breasts are milk-secreting modified sweat glands.
Well-developed and hemispherical only in women under hormonal influence
Extends horiz from lat border of sternum to midaxillary line, vert from 2nd to 6th rib
Lies on top of retromammary space, then the pectoral fascia.
Axillary tail extends upward and laterally into the axilla
Nipple is surrounded by the coloured areola.
Contents
•
•
•
•
Milk-secreting alveoli
15-20 lobules, drained by lactiferous ducts that converge independently on the axilla.
Most of the volume of the breast is produced by subcutaneous fat
Cooper’s ligaments (suspensory ligaments): fibrous septa separate the lobules attach
mammary gland to dermis.
Lymphatic drainage
•
•
!
Most lymph, especially from lateral quadrants of the breast, drain into anterior
(pectoral) lymph nodes in the axilla
Medial quadrants may drain into the parasternal lymph nodes (internal thoracic nodes)
Clinical notes
•
•
•
•
Breast enlarges normally during pregnancy and menstruation due to e.g. branching of
lactiferous ducts
Skin should feel completely mobile over breast, except with a carcinoma or abscess
Peu de orange (orange peel appearance): Puffy skin between dimpled pores may
result from breast cancer, they arise from cancerous invasion and fibrosis, which causes
shortening or pulls on the Cooper’s ligaments.
Metastasis: axillary lymph nodes are common metastatic sites from breast cancer due
to the pattern of lymphatic drainage
NIGEL FONG 2011/2012
PAGE A45
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
D. LYMPHATICS
!
Axillary lymph nodes
•
•
•
•
•
Anterior (pectoral) nodes on med axilla wall drain the ant thoracic wall and breast
Posterior (subscapular) nodes on the pos axillary fold drain the back
Lateral (humeral) nodes on the lat axilla wall drain most of the upper limb
Central nodes drain anterior, posterior, and lateral nodes.
Apical nodes receive efferent vessels from entral nodes
NIGEL FONG 2011/2012
PAGE A46
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
6. KEY REGIONS
Axilla
LOC
Pyramidal space inf to glenohumeral joint.
Passageway for neurovascular str to upper
limb, protected by adducted arm
BORD Apex
Passwageway for neurovas to enter fr neck
Base
Skin of armpit
Ant wall
Pectoralis maj & min
Pos wall
Subscapularis, Teres maj, Latissimus dorsi
Med wall
Lat wall
STR
Thoracic wall, serratus ant.
Humerus, bicipital groove
Axillary sheath containg axillary artery,
vein, and brachial plexus nerves
Axillary lymph nodes
CLINICAL
The neurovascular structures of the axilla
are vulnerable when the arm is abducted, a
tickle reflex causes most people to resume
the protected position when threatened.
Cubital fossa
LOC
BORD Sup
STR
Triangular depression on ant elbow
Imaginary line btw epicondyles
Med
Pronator teres
Lat
Brachioradialis
Floor
Brachialis, supinator
Roof
Bicipital aponeurosis
Lat
Tendon of biceps brachii
Brachial Artery
Med
Median Nerve
Roof
Median cubital vein
CLINICAL
Median cubital vein punctured for
drawing blood or intravenous
injections
!
NIGEL FONG 2011/2012
!
!
PAGE A47
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
Carpal tunnel
LOC
BORD Lat
Anterior surface of wrist, carpal arch formed by carpal bones
Scaphoid tubercle, trapezium
Med
Pisiform, hook of hamate
Roof
Flexor retinaculum bridging the med and lat sides of the arch
STR
Tendons of flexor digitorum superficialis (ant row to middle and ring finger, pos row to
index and little finger) and flexor digitorum profundus, in a common synovial sheath
Tendon of flexor pollicis longus, in a separate synovial sheath
Median nerve
NOT STR
CLINICAL
!
!
Not inside carpal tunnel: ulnar nerve & artery pass superficial to the flexor retinaculum
Carpal tunnel syndrome: compression of median nerve in carpal tunnel results in
• Sensory: paraesthesia, hypoaesthesia or anesthesia in lat 3.5 digits
• Motor: Paralysis or weakness of thenar muscles: loss of opposition
Anatomical snuffbox
LOC
BORD Med
Lat
Triangular depression, most apparent when
thumb extended, formed on posterolat wrist
by extensor pollicis tendons. Base of triangle
at wrist and apex directed into thumb.
Tendons: abductor pollicis longus, extensor
pollicis brevis
Tendon: extensor pollicis longus
Base
Scaphoid, trapezium
STR
Radial artery
Raidal nerve: terminal subcutaneous parts
CLINICAL
Scaphoid is palpable within snuffbox, with
hand in ulnar deviation, allowing assessment
of scaphoid fractures.
Radial pulse also palpable
NIGEL FONG 2011/2012
PAGE A48
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
7. DEVELOPMENT OF THE LIMBS & AXIAL SKELETON
!
A. SOMITE DEVELOPMENT
!!!!!!
!!
Somite differentiation
•
•
•
Division of paraxial mesoderm occurs at the end of the 3rd week, forming two blocks of
somites
Initial differentiation forms ventromedial sclerotome and dorsolateral dermomyotome
Dermomyotome later differentiates into myotome and dermotome
Somite derivatives
•
•
•
Sclerotome (medial) give rise to the vertebrae. The two sclerotomes on either side of
the neural tube later grow to surround the neural tube and fuse. Failure of the halves
of the vertebral arch to fuse results in spinal bifida.
Myotome (middle) gives rise to skeletal muscle (note smooth muscle differentiates from
splanchnic mesenchyme not somites)
Dermotome (lateral) gives rise to the dermis
Development of dermatomes & myotomes
•
•
•
Somatic nerves arise segmentally (motor neurons from neural tube and sensory neurons
from neural crest) in association with somites
Somatic nerves travel into the developing limbs along with the myotome & dermotome
Hence the same spinal nerve supplying a dermatome/myotome during development
supply the muscles & skin developing from that somite, forming anatomic dermatomes
& myotomes in the adult (see neuroanatomy of spine)
NIGEL FONG 2011/2012
PAGE A49
M1 NOTES IN GROSS ANATOMY
2 | UPPER LIMBS
B. LIMB DEVELOPMENT
!
Limb buds
•
•
•
Forelimb bud appears at the end of the 4th week, and the hindlimb bud 1-2 days later
(cephalocaudal sequence)
Digital rays (from mesenchymal condensations) form the fingers/toes (week 6)
Apoptosis of interdigital webs gives distinct fingers. Disorders here can result in
syndactaly or webbing of fingers/toes
Rotation of the upper limb
•
•
•
•
Early in week 7, the flexor aspect of the limbs is ventral and the extensor aspect dorsal,
thumb and great toe cranial (i.e. palms and feet facing each other)
Upper limbs rotate laterally 90º on their longitudinal axis
Hence the elbows point dorsally and the extensor muscles lie on the lateral & posterior
aspects of the limb.
Note that the lower limbs rotate medially 90º (see lower limbs)
!!!!!!!!!!!
NIGEL FONG 2011/2012
PAGE A50
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
CHAPTER 3: NORMAL STRUCTURE AND DEVELOPMENT OF THE
3 | LOWER LIMBS
!
!
1. BONES, REGIONS & MUSCLE ATTACHMENTS
A. PELVIS
Bone
•
•
•
The pelvic bone is a fused bone formed by the ilium, ischium, and pubis
The acetabulum, at the junction of the ilium, ischium, and pubis, articulates with the
head of the femur.
Surface anatomy: the anterior superior iliac spine and pubic tubercle are palpable.
Muscle attachments
1
2
3
4
5
6
Gluteus maximus
Gluteus medius
Gluteus minimus
Sartorius
Rectus femoris (straight h)
Rectus femoris (reflected h)
NIGEL FONG 2011/2012
7
8
9
10
11
12
Adductor longus
Adductor brevis
Adductor magnus
Pectineus
Gracilis
Obturator externus
13
14
15
16
17
18
Obturator internus
Gemellus superior
Gemellus inferior
Quadratus femoris
Semimembranosus
Semitendinosus &
biceps femoris (lat h)
PAGE A51
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
B. FEMUR
Bone
•
•
•
•
The femur descends at an oblique angle of 7º to the vertical.
The neck of femur is about 125º relative to the shaft
Note that the intertrochanteric line is continuous with the the pectineal line
Surface anatomy: the greater trochanter is palpable and constitutes the hip width
Ligaments
A
B
C
D
X
Y
Pubofemoral ligament
Iliofemoral ligament
Ischiofemoral ligament
Ligament of head of femur
Anterior cruciate ligament
Posterior cruciate ligament
NIGEL FONG 2011/2012
Muscle attachments
1
2
3
7
8
9
10
12
13
16
Gluteus maximus
Gluteus medius
Gluteus minimus
Adductor longus
Adductor brevis
Adductor magnus
Pectineus
Obturator externus
Obturator internus (+gemelli)
Quadratus femoris
20
21
22
23
24
25
29
30
31
32
Psoas
Iliacus
Vastus lateralis
Vastus intermedialis
Vastus medialis
Articularis genus
Biceps femoris (short h)
Gastrocnemius (med & lat h)
Plantaris
Popliteus
PAGE A52
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
Clinical notes
•
Radiography: Do not mistake the femur’s epiphyseal plates for fractures.
•
Fractures of the neck of femur (hip fracture) in adults tear the retinacular arteries
arising from the medial circumflex femoral artery and disrupt the main blood supply to
the head of the femur. As the artery to the ligament of the femoral head tends to be
inadequate in maintaining the femoral head, such a fracture tends to result in avascular
necrosis (but not in children, who have adequate blood supply to the femoral head).
Intertrochanteric fractures are of lesser consequence.
•
Thigh region
•
•
•
Borders of femur: Lateral, Medial, Linea Aspera
Surfaces of femur: Anterior, lateral, medial
Compartments of thigh: Anterior (extensor), Posterior (flexor), Medial (adductor)
C. PATELLA
Bone
•
•
•
•
Triangular bone with apex inferiorly directed
Largest sesamoid bone in the body. articulating with the femur
Attached superiorly to the quadriceps femoris tendon and distally to the patellar
ligament, which then attaches to the tibial tuberosity.
Provides a bony surface able to withstand the compression placed on the quadriceps
tendon during kneeling and the friction when the knee is flexed and extended during
locomotion
D. TIBIA & FIBULA
!
Bone
•
•
•
Fibula is non weight bearing: functions is muscle attachment and ankle joint stabilizer.
Interosseous membrane connects the tibia and fibula
Surface anatomy: Anterior border and medial border of tibia is subcutaneous
NIGEL FONG 2011/2012
PAGE A53
M1 NOTES IN GROSS ANATOMY
Muscle attachments
22-25
Ligamentum patellae (Quadriceps femoris tendon via patella)
4, 11, 18
Pes anserinus: [la] Sartorius, Gracilis, Semitendinosus [med]
17 Semimembranosus
37
Fibularis longus
26 Soleus
38
Fibularis brevis
32 Popliteus
39
Fibularis tertius
!
3 | LOWER LIMBS
27
28
33
34
35
36
Tibialis posterior
Tibialis anterior
Flexor hallucis longus
Flexor digitorum longus
Extensor hallucis longus
Extensor digitorum longus
!
Leg region
•
•
•
•
•
Surfaces of tibia & fibula:
lateral, medial, posterior.
Borders of tibia: anterior,
interosseous, medial
Borders of fibula: anterior,
interosseous, posterior
Compartments
of
leg:
anterior, posterior, lateral
Posterior compartment is
split into deep and superficial
by transverse intermuscular
septum
NIGEL FONG 2011/2012
!
PAGE A54
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
!
E. FOOT
Bone
•
•
•
•
•
Metatarsals and phalanges numbered 1-5 from medial to lateral (great toe to little toe)
Abduction and adduction defined with respect to the axis of the 2nd toe.
Each cuneiform articulates with its corresponding metatarsal, while the cuboid
articulates with metatarsal 4 & 5
The 1st and 5th metatarsals have tuberosities for tendon attachment
Surface anatomy: the tuberosity of the 5th metatarsal projects laterally over the
cuboid and is palpable.
NIGEL FONG 2011/2012
PAGE A55
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
Function of the arches of the foot
•
•
•
Foot has 3 arches: medial longitudinal, lateral longitudinal, and transverse
Allows foot to better support body: pliable and can adapt itself to uneven surfaces
Better propel body forward: long flexor muscles and small foot muscles can plantarflex
foot & toes, assisting forward propulsive action of gastrocnemius and soleus in takeoff.
Support of medial longitudinal arch
Bones:
Ligaments:
Concave proximal medial cuneiform receives navicular
Concave proximal navicular surface receives rounded talar head
Talus is the keystone
Sustentaculum tali of the calcanus holds up the talus
Plantar calcaneonavicular ligament (spring ligament)
Plantar aponeurosis
Tendons of flexor digitorum longus & brevis, flexor hallucis longus & brevis
Support:
Tibialis anterior & posterior
Medial ligament of ankle joint
Support of lateral longitudinal arch
Bones:
Ligaments:
Cuboid is keystone
Long & short plantar ligaments
Plantar aponeurosis
Tendon of flexor digitorium longus & brevis
Support:
Peronus longus & brevis
Clinical notes
•
Flat foot (pes planus): Collapse of longitudinal arch due to congenital reasons or
fatigue of muscular support results in stretched ligaments and pain on walking.
NIGEL FONG 2011/2012
PAGE A56
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
2. JOINTS OF THE LOWER LIMB
movements of joints are covered under muscles
A. HIP JOINT
!
Articulation
•
•
•
•
Between the hemispherical head of femur and the lunate surface of the deep
hemispherical acetabulum formed by the ischium, ilium, and pubis
Acetabulum cavity is deepend by fibrocartilaginous acetabular labrum
Articular surface of acetabulum deficient inferiorly at the acetabular notch, but this is
bridged by the transverse acetabular ligament
Highly stable joint: 2/3 of the femoral head fits into the deep acetabulum and its
labrum
Cartilage
•
•
Articular surfaces covered by hyaline cartilage
Except fovea on femoral head to which ligament of femoral head is attached
Type
•
•
Synovial triaxial ball & socket joint
Allows flexion, extension, abduction, adduction, medial and lateral rotation
Synovial membrane
•
•
•
•
Lines capsule, attached to margins of articular surfaces
Produces viscous synovial fluid to lubricate joint
Ensheaths ligament of head of femur
Covers neck of femur & reflects onto fibrous membrane
NIGEL FONG 2011/2012
PAGE A57
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
Capsule
•
•
•
•
Fibrous capsule encloses the joint
Proximal attachment: acetabular labrum
Distal attachment: Intertrochanteric line (ant) and intertrochanteric crest (pos)
At the attachment to the intertrochanteric line, some capsule fibres and accompanying
blood vessels are reflected upwards along the neck as retinacula; these contain
retinacular blood vessels supplying the head and neck of femur
Ligaments
•
Iliofemoral, pubofemoral, and ischiofemoral ligaments are oriented in a spiral fashion
and are taut when the joint is extended to stabilize the joint.
LIGAM.
SHAPE
PELVIC ATT
FEMUR ATT
LOC & FUNCTION
Iliofemoral
Y
Ant inf iliac spine
Intertroch. Line
Ant/Sup: Prev. hyperextension
Pubofemoral
∆
Obturator crest &
sup. Pubic ramus
Continous with
iliofemoral lig
Ant/Inf: Prev. overabduction
Ischiofemoral
∆
Ischium
Greater troch.
Posterior support
Acetabular fossa
Fovea
Synovial fold with blood vessel
Lig of head of femur
(lig teres)
Fatty pad
•
Fatty pad in acetabular fossa fills part of the acetabular fossa not covered by the
ligament of head of femur
Blood supply
•
•
Mainly from an anastomosis formed by the medial & lateral circumflex femoral artery
Artery to head of femur (a branch of the obturator artery) transverses the ligament of
head of femur, but this is insufficient supply for the head of femur in adults.
Nerve supply
•
•
•
•
Femoral
Obturator
Nerve to quadratus femoris
Sciatic nerve (superior gluteal nerve)
NIGEL FONG 2011/2012
PAGE A58
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
Relations
•
•
•
•
•
[ant] Iliopsoas, pectineus, femoral artery/nerve/vein
[pos] Piriformis, obturator internus, gemelli, quadratus femoris, sciatic nerve
[lat] Iliotibial tract, gluteus maximus
[sup] Gluteus maximus/medius/minimus
[inf[ Obturator externus
B. KNEE JOINT
!
Articulation
•
•
Between the lateral & medial femoral condyle (rounded in flexion, flat in extension)
and the lateral & medial tibial condyle
Between patellar surface of distal femur and patella
Cartilage
•
Articular surfaces covered by hyaline cartilage
Type
•
•
•
Femoral-tibial articulation: synovial modified hinge joint
Allows flexion, extension, limited medial & lateral rotation
Femoral-patellar articulation: plane joint, allows gliding movements only
Menisci
•
•
•
•
•
2 (medial & lateral) C-shaped fibrocartilage plates improve congruency between
femoral and tibial condyles by deepening articular surface of tibial condyles to receive
convex femoral condyles
Distally: attached to facets in the intercondylar region of the tibial plateau
Superiorly: surfaces in contact with tibial condyles
Thicker at periphery and thinner towards interior
Medial meniscus attached to joint and ligament
Synovial membrane
•
•
•
•
1 common synovial cavity for both articulations
Lines capsule, attached to margins of articular surfaces and superior & inferior outer
margins of menisci
Separated from patellar ligament by infrapatellar fatty pad
Produces viscous synovial fluid to lubricate joint
Capsule
•
•
•
•
Fibrous capsule encloses the joint
[ant] Deficient, replaced by quadriceps tendon, patella, and ligaments
[med] Blends with tibial collateral ligament
[lat] Separated from fibular collateral ligament
NIGEL FONG 2011/2012
PAGE A59
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
Ligaments
LIGAMENT
FEMUR ATT.
TIBIAL ATT.
FUNCTION & NOTES
Patellar
Patella, inferior border
Tibial tuberosity
Cont. of quad. Fem.
Tendon
Tibial collateral
Med epicondyle
Med prox tibia
Att. To capsule & med
meniscus: higher injury
Fibular collateral
Lat epicondyle
Fibula, head
Not attached to capsule
Ant cruciate
Lat wall
Ant
Pos cruciate
Med wall
Prev ant
•
Prev pos
Oblique popliteal
Pos tendinous expansion of semimembranosus
intercondylar
fossa
Pos
intercondylar
area
displacement of
tibia on femur
Strengthen pos. capsule
Bursa
•
•
•
•
•
Bursa help to reduce friction between moving surface and include
Suprapatellar: large continuation of articular cavity between distal end of femur and
quadriceps femoris tendon, pulled away from joint by articularis genus during extension
of knee
Prepatellar: Between skin & patella
Superficial infrapatellar: Between skin & patellar ligament
Deep infrapatellar: Between patellar ligament & tibia
Blood supply
•
Genicular anastomosis from branches of femoral, popliteal, ant & pos recurrrent tibial,
circumflex fibular artery
Nerve supply
•
•
•
•
Femoral
Tibial
Common fibular
Obturator
NIGEL FONG 2011/2012
PAGE A60
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
Locking & Unlocking
•
•
•
When weightbearing knee is fully extended, medial rotation of femur on tibia (lateral
rotation of tibia on femur) locks the knee.
Locking makes the joint more stable, so the thigh and leg muscles can relax briefly
To unlock, the popliteus muscle contracts, rotating femur laterally on a fixed tibia
Clinical notes
•
•
•
•
•
•
Lateral collateral ligament injury: Forced adduction of the tibia tears the lateral
collateral ligament
Medial collateral ligament injury: Forced abduction of the tibia tears the medial
collateral ligament. They are usually accompanied by medial meniscus damage due to
the firm attachment of the tibia collateral ligament to the medial meniscus.
Anterior cruciate ligament tears: Hyperextension may tear the anterior cruciate
ligament, giving the anterior drawer sign: femur can slide posteriorly on tibia.
Posterior cruciate ligament tears: Less common
Prepatellar bursitis: Inflammation due to friction between skin and patella, e.g. in
housemaids who work on their knees (hence “housemaid’s knee”).
Infrapatellar bursitis: Inflammation due to friction between skin and tibial
tuberosity, e.g. in excessive kneeling of clergymen (hence “clergyman’s knee”).
!
!
C. ANKLE (TALOCRURAL) JOINT
!
Articulation
•
•
•
•
Superiorly: mortise formed by deep bracket-shaped socket of inferior tibia, medial
malleolus of tibia and lateral malleolus of fibula
Inferiorly: Articular half-cylindrical superficial talar end
Mortise is deep and malleoli grip talus tightly
More stable when dorsiflexed
Cartilage
•
Articular surfaces covered by hyaline cartilage
Type
•
•
Synovial hinge joint
Allows dorsiflexion and plantarflexion
Synovial membrane
•
•
Lines capsule, attached to margins of articular surfaces
Produces viscous synovial fluid to lubricate joint
Capsule
•
Fibrous capsule encloses the joint
NIGEL FONG 2011/2012
PAGE A61
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
Ligaments
LIGAMENT
SUPERIOR ATT
INFERIOR ATT
Medial (Deltoid) ligament – Large & Strong
Tibionavicular
Ant. Tibiotalar
Pos. tibiotalar
Navicular tuberosity
Tibia, Medial malleolus
Tibiocalcaneal
Talus, ant
Talus, med tubercle
Calcaneus, sustentaculum tali
Lateral ligament
Ant. talofibular
Pos. talofibular
Calcaneofibular
Talus, neck
Fibula, Lateral malleolus
Talus, lateral tubercle
Calcaneal, lat. side
Blood supply
•
Malleolar branches of fibular, anterior & posterior tibial arteries
Nerve supply
•
•
Tibial
Deep fibular
NIGEL FONG 2011/2012
PAGE A62
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
D. SUBTALAR (TALOCALCANEAL) JOINT
!
Articulation
•
•
Proximally: Large posterior facet on inf. talar surf
Distally: Corresponding talar facet on sup. Calcaneal surf
Cartilage
•
Articular surfaces covered by hyaline cartilage
Type
•
•
Synovial plane joint
Allows gliding and rotation, as involved in inversion and eversion
Synovial membrane
•
•
Lines capsule, attached to margins of articular surfaces
Produces viscous synovial fluid to lubricate joint
Capsule
•
Fibrous capsule encloses the joint
Ligaments
•
•
Reinforced by medial, lateral, and posterior talocalcaneal ligament
Interosseous talocalcaneal ligament (from sulcus tali to sulcus calcanei) in tarsal sinus
binds the bones together
!
Blood supply
•
Posterior tibial & fibular arteries
Nerve supply
•
•
Medial / lateral plantar nerve
Deep fibular nerve
!
NIGEL FONG 2011/2012
!
PAGE A63
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
3. MUSCLES OF THE LOWER LIMBS
!
A. POSTURE AND GAIT
The lower limbs are designed for maximum
stability and minimum muscular activity when
standing at ease.
Standing at ease
•
•
•
•
Hip joint at its most stable: extension of
thigh makes ligaments taut
Knee joint at its most stable: Centre of
gravity anterior to knee, facilitating
extension, joint surfaces become larger
and more stable in extension
Forward sway resulting from centre of
gravity being anterior to the leg is
countered by periodic bilateral calf
muscle plantarflexion
Lateral sway contered by hip abductors
acting through iliotibial tract
Walking
•
Gait cycle illustrates a stance and a swing phase.
•
•
Heel strike: Tibialis anterior eccentrically contracts, lowering forefoot to ground
Loading response: Quadriceps eccentrically contracts to accept weight (esp. downhill
walk) and absorb shock of heel strike
Midstance & push-off: Triceps surae (gastrocnemius & soleus) plantarflex foot
Swing phase: Iliopsoas & rectus femoris flex hip, knee follows by momentum, tibialis
anterior dorsiflex to clear foot of ground
Swing phase: If against gravity e.g. uphill, quadriceps femoris contract to extend knee
Note that gluteus medius and minimus of the stance foot abduct the hip to prevents
excessive pelvic tilt on the contralateral side
Arches of foot continually supported by leg muscles
Gluteus maximus is reserved for rising from a sitting position or walking uphill, it is
unused when standing, and only minimally when walking on level ground
•
•
•
•
•
•
!
NIGEL FONG 2011/2012
PAGE A64
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
B. GLUTEAL MUSCLES
!
Deep
NERVE
ORIGIN
19
Piriformis
L5-S2 Br
Ant. sacrum
13
Obturator Internus
Obturator membrane
14
Gemellus sup.*
N. to
obturator int.
15
Gemellus inf.*
16
Quadratus femoris
N. to quad.
femoris
Ischial spine
Ischial tuberosity
INSERTION
ACTION ON
HIP
Trochanteric fossa &
med. side greater
trochanter
LatR
& Ab
Intertroch. crest
LatR
KNEE
-
* Obturator internus and the two gemelli may together be termed triceps coxae
!
Superficial
1
Gluteus maximus
2
Gluteus medius
3
Gluteus minimus
4
Tensor fascia lata
NERVE
ORIGIN
INSERTION
Inf gluteal
Sacrum, coccyx, ilium
pos. to pos gluteal line
Ext ilium btw. ant &
pos gluteal line
Sup. gluteal
Ext ilium btw. ant &
inf gluteal line
Iliac crest
ACTION ON
HIP
KNEE
Gluteal tuberosity &
Iliotibial tract
Ext
Ext
Greater trochanter
Abd,
MedR
-
Iliotibial tract
-
Ext
!
Clinical notes
•
•
!
Weakness of the gluteus medius and minimus or superior gluteal nerve injury results in
a gluteal gait (list of the body over to the weakened side to place centre of gravity
over supporting limb), and positive Trendelenburg test (when standing on one leg,
pelvis on unsupported side descends).
Gluteus maximus provides a large absorption area for intramuscular injections. These
should be given in the upper outer (lateral) quadrant to prevent sciatic nerve damage.
Note that the gluteal region is not restricted to the most prominent part of the buttock
and in fact extends up to the anterior superior iliac spine.
NIGEL FONG 2011/2012
PAGE A65
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
C. ANTERIOR THIGH MUSCLES
Muscle
NERVE
ORIGIN
INSERTION
L1-L3:
ant rami
T12-L5: transverse process,
bodies, intervertebral discs
ACTION ON
HIP
KNEE
Lesser trochanter
Flex
Flex
Iliopsoas:
20
Psoas maj
21
Iliacus
Ilium: Iliac fossa
4
Sartorius
Ilium: Ant sup iliac spine
Tibia: pes anserinus
Flex
10
Pectineus*
Pubis: Sup ramus
Femur: pectineal l.
Fx,
Ad
Quadriceps Femoris:
Femoral
22
Vastus lateralis
Femur: lat lip linea aspera
23
Vastus intermedius
Femur: ant & lat surf
24
Vastus medialis
Femur: med lip linea aspera
5
6
Rectus femoris
[straight head]
[reflected head]
Ilium: Ant inf iliac spine
Ilium: Sup to acetabulum
Tibial tuberosity
via quadric. tendon,
patella, and patella
tendon (Vastus
med also attaches
to patella)
Ext
Flex
!
Identification from ant view
•
•
•
•
An N is formed by the (“GST”)
gracilis, sartorius, and tensor
fascia lata, with the sartorius
diagonal.
Rectus femoris is straight and
superficial
Adductor longus is the most
superficial, adductor magnus the
deepest.
Sartorius overlays the adductor
canal
* Pectineus is also considered a muscle
of medial compartment of thigh
Clinical notes
•
•
•
Quadriceps tendon jerk is elicited by a firm strike on the patella ligament with patient
sitting on edge of bed and legs dangling. This tests the function of the femoral nerve
and L2-L4 (especially L3) spinal nerves.
Sartorius can flex, abduct, and laterally rotate thigh, and flex and medially rotate the
leg. The combined actions of the sartorius produce a cross-legged sitting position.
Sartorius and gracilis are weak muscles.
NIGEL FONG 2011/2012
PAGE A66
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
D. MEDIAL THIGH MUSCLES
Muscle
NERVE
7
Adductor longus
8
Adductor brevis
9
Add. magnus
(adductor part)
11
Gracilis
12
Obturator ext.
Obturator
ORIGIN
INSERTION
Pubis: Body
Tibia: linea aspera (mid 1/3)
Pubis: Ischiopubic
ramus
Obturator membrane
Tibia: linea aspera (upp 1/3)
Tibia: linea aspera, med.
Supracondylar line
ACTION ON
HIP
KNEE
Ad
-
Tibia: pes anserinus
Flex
Trochanteric fossa
LatR
Flex
Adductor canal (subsartorial canal, Hunter canal)
•
•
•
•
Distal continuation of femoral triangle.
Intramuscular passage for femoral artery, vein, and branches of the femoral nerve
Bounded by [ant/lat] vastus medialis, [pos] adductor longus & magnus, [med] sartorius
Vessels pass from the adductor canal to the popliteal fossa through the adductor
hiatus, a gap between the aponeurotic adductor and tendinuous hamstring attachments
of the adductor magnus.
NIGEL FONG 2011/2012
PAGE A67
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
E. POSTERIOR THIGH MUSCLES
!
Muscle
29
Biceps femoris
[short head]
NERVE
ORIGIN
INSERTION
Sciatic,
peroneal div
Femur: lat lip
linea aspera
Fibula head
Sciatic,
tibial div
Ischial tuberosity
[long head]
18
Semitendinosus
19
Semimembranosus
9
Adductor magnus
(hamstring part)
ACTION ON
HIP
LEG
LatR
Ext
Flx
Tibia: pes anserinus
MedR
Tibia: med condyle
Femur:
adductor tubercle
Ext
Ad.
Identification from pos view
•
•
•
Semimembranosus and semitendinosus
on medial side, with semimembranosus
more medial
Biceps femoris on lateral side
Semimembranosus is membrane-like
distally, semitendinosus is tendon-like
distally.
Clinical notes
•
Hamstrings are commonly torn
F. ANTERIOR & LATERAL LEG MUSCLES
Anterior leg
28
Tibialis ant.
35
Ext hallucis longus
36
Ext digitorum longus
39
Fibularis* tertius
NERVE
Deep
fibular*
ORIGIN
INSERTION
Tibia: lat &
inteross. mem
Med cuneiform
& metatarsal 1
Distal phalanx 1
Fibula: ant
shaft
Distal & mid
phalanx 2-5
Metatarsal 5
ACTION ON
ANKLE
FOOT
Invert
Dorsiflex
Evert
TOES
Ext 1
Ext 2-5
-
*Fibularis longus = peroneus longus, deep fibular nerve = deep peroneal nerve, and so on
NIGEL FONG 2011/2012
PAGE A68
M1 NOTES IN GROSS ANATOMY
Lateral leg
37
Fibularis* longus
38
Fibularis* brevis
NERVE
Sup.
Fibular*
3 | LOWER LIMBS
ORIGIN
INSERTION
Fibula: upp lat
Med cuneiform
& metatarsal 1
Fibula: inf lat
Tuberosity of
metatarsal 5
ACTION ON
ANKLE
FOOT
Evert
TOES
-
Identification of ant/lat view
•
Note that the anterior compartment is lateral to the palpable subcutaneous anterior
border of tibia. The lateral compartment does not start until fibularis longus.
NIGEL FONG 2011/2012
PAGE A69
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
G. POSTERIOR LEG MUSCLES
Superficial
31
NERVE
Plantaris
ORIGIN
Gastrocnemius
[med head]
[lat head]
26
Soleus
KNEE
FOOT
Femur: Inf lat supracondylar line
Triceps Surae:
30
ACTION ON
INSERTION
Tibial
Femur: Sup to med condyle
Femur: Sup to lat condyle
Pos calcaneus
via calcaneal
(archilles
tendon)
Flex
Tibia & Fibula: Shaft
Pflex
-
!
!
Deep
NERVE
32
Popliteus
33
Flx hallucis longus
34
Flx digitorum long.
27
Tibialis posterior
Tibial
ORIGIN
INSERTION
Femur: lat
condyle
Tibia: pos prox
Fibula: pos
Dist phalanx 1
Tibia: pos med
Dist phalanx 2-5
Pos interos mem
Navicular tuber.
ACTION ON
ANKLE
FOOT
TOES
Unlock knee via lateral
rotation of femur on tibia
Plantarflex
Invert
Flx 1
Flx 2-5
-
Identification of pos view
•
•
•
Gastrocnemius is proximal to soleus, and forms the inferomedial and inferolateral
boundaries of the popliteal fossa
Flexor hallucis longus originates from the lateral side of the leg but its tendon crosses
over that of flexor digitorum longus in the foot to insert at the medial great toe
Arrangement of structures in the tarsal tunnel (flexor retinaculum) from med to lat:
tibialis posterior, flx dig longus, pos tibial artery (and venae comitantes), tibial nerve,
flx hallucis longus (sometimes deep). [“Tom, Dick, ANd Harry”]
NIGEL FONG 2011/2012
PAGE A70
!
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
Clinical notes
•
•
•
•
Calcaneal tendon jerk tests for damage to tibial nerve or S1 and S2 spinal segments
that supply the tibial nerve
Triceps surae contracture i.e. shortening of calcaneal tendon due to fibrosis may
occur as the result of an injury
Plantaris is a vestigial muscle
Compartment syndrome: Lower limb fascia is strong and compartments are closed
spaces. Any increase in pressure within a compartment e.g. due to muscle inflamation
may compress muscles and nerves within that compartment, adversely affecting
circulation and causing ischemia in structures distal to the compressed area
H. MUSCLES OF FOOT
Muscles of the foot are clinically unimportant because fine control of the toes are not
important, and it suffices to know:
Dorsum of foot (superficial to deep)
•
•
Tendons of extensor hallucis longus & extensor digitorum longus
Extensor digitorum brevis & extensor hallucis brevis
Sole of foot (superficial to deep)
•
•
•
Abductor hallucis, Flexor digitorum brevis, Abductor digiti minimi
Tendons of flexor hallucis longus & flexor digitorum longus
Quadratus plantae, which assists flexor digitorum longus in flexing the digits
!
NIGEL FONG 2011/2012
PAGE A71
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
4. MAJOR NERVES OF THE LOWER LIMB
!
A. ANTERIOR & MEDIAL THIGH
Femoral Nerve
ORIGIN
COURSE
TERM
Lumbar plexus (L2-L4)
In abdomen within psoas maj, runs downwards
& lat btw psoas & iliacus.
Enters thigh through femoral triangle
• Outside femoral sheath
• Lat to femoral artery, vein, lymphatics
• Deep to midpoint of inguinal lig.
Saphenous n. = term cutaneous branch
Through adductor canal w femoral vessels
Descends with great saphenous vein
SS skin on medial ankle and foot
BRANCH
Branches to ant thigh muscles
Articular branches to hip and knee joint
Cutaneous branches to anteromedial thigh
SS
Motor
Sensory
CLINICAL
Ant thigh muscles except psoas maj
Hip, knee, anteromedial thigh, med ankle & foot
Important not to injure femoral nerve when
accessing femoral artery / vein at femoral
triangle.
!
Obturator Nerve
ORIGIN
COURSE
TERM
BRANCH
SS
Motor
Sensory
Lumbar plexus (L2-L4)
In abdomen within psoas maj
Lat pelvic wall: cross pelvic brim in front of
sacroiliac jt, behind comon iliac vessels
Obturator canal to medial thigh
Splits into ant & pos branches
Pos branch: btw adductor brevis & magnus
• SS Obturator ext, add. brevis & magnus
Ant branch: btw adductor longus & brevis
• SS adductor longus, brevis, gracilis
• Cutaneous br to med thigh
Med thigh muscles except hamstring part of add.
magnus and pectineus.
Medial thigh
!
!
NIGEL FONG 2011/2012
PAGE A72
M1 NOTES IN GROSS ANATOMY
B. SCIATIC
NERVE
!
3 | LOWER LIMBS
& BRANCHES
Sciatic Nerve
ORIGIN
COURSE
TERM
BRANCH
Lumbosacral plexus (L4-S3)
Through greater sciatic foramen inf to piriformis
• Deep to gluteus maximus
• Most lateral structure emerging through greater sciatic foramen
Pos thigh deep to biceps femoris
Divide into tibial and common fibular nerve at apex of popliteal fossa (see “spaces”)
Division into terminal branches may occur in upper thigh or even pelvis
Branches to pos. thigh muscles
Articular branches to all joints in lower limb (no branches in gluteal region)
SS
Motor
Sensory
CLINICAL
!
Tibial division supplies pos. thigh muscles
(except short head of biceps femoris, but inc hamstring part of add magnus)
All muscles in leg and foot
Most skin in leg and foot
Largest nerve in the body
Injury may result from misplaced gluteal injection, compression by piriformis. Complete
section is rare but it may result in
• Paralysis of hamstrings (but knee flexion by sartorius and gracilis still possible)
• Paralysis of all leg muscles, resulting in foot drop
• Sensory loss below knee, except a medial strip SS by saphenous nerve SS
NIGEL FONG 2011/2012
PAGE A73
M1 NOTES IN GROSS ANATOMY
ORIGIN
COURSE
Tibial Nerve
Through popliteal fossa
• Lies on tibialis posterior
Through tarsal tunnel
• Btw flexor digitorum longus
and flexor hallucis longus
BRANCH
Fibular (Peroneal) Nerves
Div of sciatic nerve into tibial and common fibular nerves at apex of popliteal fossa
• Lat and sup to femoral vein
and then art
• Sup to popliteus
Pos leg: w pos tibial art & vein
TERM
3 | LOWER LIMBS
Common fibular n.
Follow med. border of biceps femoris tendon
Pass over pos. fibular head and wind
subcutaneously around fibular neck, divides into
deep & sup fibular n.
Sup fibular n.
Deep fibular n.
Leg: Lat compartment
Pierce fascia & bec
subcut. in distal 1/3
Leg: Ant compartment
Lie on inteross. mem.
Divides into med & lat plantar
n at flexor retinaculum
(SS most muscles and sole of foot)
Cutaneous branches
continue to foot
(SS dorsum of foot)
Enter foot deep to ext
retinaculum
Br to pos leg muscles
Br to lat leg muscles
Br to ant leg muscles
Articular branches to knee joint
Common fibular n: articular branches to knee joint
Sural nerve (cutaneous)
SS
Motor
Sensory
• Fr med sural cutaneous n fr tibial n & sural communicating br fr common fibular n
• Desc btw gastrocnemius heads to become sup. and desc with small saphenous vein
• Cutaneous SS pos & lat leg, lat foot
Pos leg, most foot muscles
Lat leg muscles
Ant leg & some foot musc
Knee, pos & lat leg, lat foot.
CLINICAL
NIGEL FONG 2011/2012
Dorsum of foot
Dorsum, 1st interdig cleft
Common fibular nerve often injured at subcut loc
over fibular neck, causing footdrop.
PAGE A74
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
5. BLOOD SUPPLY OF THE LOWER LIMB
!
A. ARTERIAL SUPPLY
!
Femoral Artery
ORIGIN
COURSE
TERM
BRANCH
Continuation of ext. iliac artery at
midpoint of inguinal ligament
• Deep to inguinal ligament, within
femoral sheath
• Med to femoral nerve, lat to femoral
vein.
Through femoral triangle (within femoral
sheath) and adductor canal
Pass through adductor hiatus to enter
popliteal fossa
Continues as popliteal artery past the
adductor hiatus
Gives profunda femoris artery
• Lat & med circumflex femoral art
SS head & neck of femur, hip joint, adj
muscles
• 4 perforating arteries
Pass through adductor magnus to supply med
& pos thigh muscles
Muscular branches to extensor and some adductor muscles
CLINICAL
!
In the femoral triangle just below mid-point of inguinal ligament
•
•
•
•
Can palpate femoral pulse
Can obtain arterial blood samples
Can insert catheter
Important to avoid injury to femoral nerve which lies laterally
Popliteal Artery
ORIGIN
COURSE
TERM
BRANCH
Continuation of femoral artery at adductor hiatus
Run through popliteal fossa (diagram: see
popliteal fossa)
• Sup & lat to popliteal vein & artery
Divide into anterior & posterior tibial arteries at
lower border of popliteus
5 genicular arteries participating in arterial
anastomosis, to ensure adequate blood supply
even if popliteal artery itself if kinked e.g. during
knee flexion
Posterior tibial artery
ORIGIN
COURSE
TERM
BRANCH
Popliteal art inf to lower border of popliteus
Posterior compartment of leg
• With tibial nerve
Divide into anterior & posterior tibial arteries at
lower border of popliteus
Gives fibular art, which descends in pos leg
NIGEL FONG 2011/2012
PAGE A75
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
Anterior tibial artery
ORIGIN
COURSE
TERM
Continuation of popliteal art in popliteal
fossa
Anterior compartment of leg
• With deep fibular nerve
Enters foot as dorsalis pedis artery
Dorsalis pedis artery
ORIGIN
COURSE
TERM
BRANCH
CLINICAL
Ant tibial artery inf to ext retinaculum
Between tendon of extensor hallucis longus
and extensor digitorum longus
Ending as deep plantar artery (connects
with lat plantar art to form plantar arch)
Branches to tarsal bones and 1st dorsal
metatarsal arteries
Dorsalis pedis pulse can be felt in front of
ankle (between EHL and EDL tendon)
!
B. VENOUS DRAINAGE
!
ORIGIN
COURSE
Great saphenous vein
Small saphenous vein
Foot: union of dorsal vein of great toe and
dorsal venous arch of the foot
Foot: union of dorsal vein of little toe
with dorsal venous arch
Ant to medial malleolus
Pos to lat malleolus & lat border of
calcaneal tendon
Ascend on pos side of leg
Ascend on medial side of leg
TERM
BRANCH
• With saphenous nerve
Pos to medial condyle of femur
• With sural nerve
Penetrates deep fascia
Ascend between gastrocnemius heads
Empties into femoral vein through
saphenous opening in fascia lata
Empties into popliteal vein in popliteal
fossa
Anastomosis and perforating veins shunting blood into deep veins
!
!
NIGEL FONG 2011/2012
PAGE A76
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
Venous blood flow
•
•
•
Musculovenous pump: muscular contractions propel blood in deep veins towards the
heart against gravity
Blood received by superficial (saphenous) veins continually shunted through perforating
veins into deep veins.
Venous valves are cusps of endothelium that fill from above and occlude the lumen of
the vein when full, preventing distal backflow of blood, making flow unidirectional.
Clinical notes
•
•
•
•
Deep vein thrombosis (economy-class syndrome): formation of blood clot in deep
vein that can break free to travel to the heart (causing pulmonary thromboembolism)
or lung (obstructing pulmonary artery) with devastating consequences. This may result
from muscular inactivity during long flights, or incompetent fascia that fails to resist
muscle expansion, reducing the effectiveness of the musculovenous pump.
Varicose veins: result from incompetent veins that have dilated such that valve cusps
do not close, allowing blood to flow inferiorly or remain stagnant. This arises due to
long periods of standing or increased abdominal pressure obstructing the vena cava in
pregnant women. Varicose veins give pain and possibly venous ulcers.
Venous cutdown of great saphenous vein ant to med malleolus is used to start drips
in children / infants
Great saphenous vein can be removed and used for bypasses, if deep veins are intact.
Deep Veins
•
•
Deep veins accompany major arteries and their branches as paired venae comitantes.
To note: Popliteal vein and femoral vein
C. LYMPHATICS
!
Inguinal nodes
•
•
•
Superficial inguinal nodes, located along the inguinal ligament, receive lymph from the
gluteal region, perineum, and superficial regions of the lower limb
Deep inguinal nodes medial to the femoral vein receive lymph from the femoral vessels
and the glans penis/clitoris in the perineum
Inguinal nodes drain into external iliac nodes
NIGEL FONG 2011/2012
PAGE A77
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
6. KEY REGIONS
Femoral triangle
LOC
BORD Sup
Med
Lat
Floor
Roof
STR
Lat
Triangular depression on ant
thigh appearing when thigh is
flexed, abducted, and lat rotated.
Continues distally as the adductor
canal (see muscles)
Inguinal lig (from ant sup iliac
spine to pubic tubercle)
Adductor longus, lat border
Sartorius
Iliopsoas (lat), Pectineus
Fascia lata
Skin
Femoral nerve
Femoral artery
Femoral vein
Med
!
Femoral canal
Deep inguinal lymph
nodes
Within
femoral
sheath
RELAT
Great saphenous vein drains into
femoral vein through saphenous
opening in the femoral triangle
CLINICAL
Femoral artery and vein accessed
at midpoint btw ASIS and pubic
tubercle. Important not to injure
femoral nerve.
Gateways to the lower limb
NIGEL FONG 2011/2012
PAGE A78
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
Popliteal fossa
LOC
BORD
Sup/Lat
Sup/Med
Inf/Med
Inf/Lat
Floor
STR
Lat
Diamond-shaped depression pos to
knee joint
.
Biceps femoris
Semimembranosus (med) &
Semitendinosus (lat)
Gastrocnemius, med head
Gastrocnemius, lat head
Femur, popliteal fascia, joint
Femoral nerve
Sup
Femoral vein
Med
RELAT
CLINICAL
!
!
Femoral artery
Deep
Femoral n divides into tibial
&common fibular n
Small saphenous vein drains into
popliteal vein
Popliteal art can give aneuysm
here
NIGEL FONG 2011/2012
!
PAGE A79
M1 NOTES IN GROSS ANATOMY
3 | LOWER LIMBS
7. DEVELOPMENT OF THE LOWER LIMBS
!
Rotation of the lower limb
•
•
•
•
The hindlimb bud develops from L2-S2 segments
Development is largely similar to that of the upper limb, except that the lower limbs
rotate medially 90º (vs laterally 90º for the upper limbs)
Hence the knees face anteriorly and the extensor muscles lie anteriorly
Radius and tibia are homologous bones, as are the ulna and fibula.
!
NIGEL FONG 2011/2012
PAGE A80
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
CHAPTER 4: NORMAL STRUCTURE AND NEUROANATOMY OF THE
!
!
4 | BACK, SPINE & SPINAL CORD
1. MUSCULOSKELETAL STR
!
A. SPINE
!
!
!
!
!
Vertebrae
•
•
Vert column: 7 cervical, 12 thoracic, 5 lumbral, 5 fused sacral, coccyx
- Having many small bones gives flexibility
- Going sup – inf, vertebrae gradually become larger: greater weight to bear
Features
- Vertebral body: main weight-bearing part; contains hematopoietic marrow
-
•
•
Spinal (vertebral) canal containing & protecting the spinal cord & meninges.
1 median spinous process & 2 transverse processes provide attachment for
deep back muscles.
Vertebral (neural) arch formed by pedicle (connect body to transverse process)
& lamina (connect transverse process to spinous process)
Distinguishing features of regional vertebrae
- Note C1-C2 are atypical
- Cervical vertebrae: with foramen transversarium for vertebral art (except C7)
- Thoracic vertebrae: with costal facets for articulation with ribs
- Lumbar vertebrae: lack the features above.
Surface anatomy:
- C7 spinous process is most evident superficially
- Horizontal line joining highest points of iliac crests passes through L4-L5 IV disc
Clinical notes
•
•
There may be variations in no. of vertebrae (ex. no. of cranial vertebrae v consistent)
Spina bifida: neural arches fail to fuse in the midline. This may be asymptomatic
(location indicated by a tuft of hair), or be associated with herniation of meninges
(meningocele) and/or spinal cord (meningomyelocele)
NIGEL FONG 2011/2012
PAGE A81
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
Intervertebral joints
•
Symphyses (2º cartilaginous jt): vertebral bodies
united by strong intervertebral discs
Anulus fibrosis: fibrocartilage rings forming
circumference of IV disc
- Nucleus pulposus: avascular IV disc core,
“pulpy” & cartilaginous for shock absorption.
- Can flex, extend, laterally flex, rotate
Zygapophysial (facet) joints btw vertebral
arches / articular processes:
- Plane synovial joints permitting gliding mvmt
- Limit movement of IV joints.
Supported by ligaments:
- Ant longitudinal lig: limits hyperextension
- Pos longitudinal lig: resists hyperflexion
- Ligamentum flava: join lamina of adj
vertebral arch
- Others: interspinous lig, intertransverse etc.
-
•
•
!
Clinical notes
•
Herniation of nulcus pulposus (“slipped disc”)
-
•
•
Nucleus pulposes ‘squeezed’ pos, throu anulus fibrosis
May herniate into vertebral canal, compress sp cord.
Acute lower back pain due to pressure on ligaments,
anulus fibrosis, inflammation
- Referred chronic pain usu. from compression of spinal
nerve inf to herniated disc.
- Most common at L4-L5 / L5-S1 levels; compression of
sciatic n causes sciatica (pain fr lower back and hip
radiating down back of thigh to leg)
Whiplash injury: severe hyperextension of neck tears ant
longitudinal lig.
Injury or osteoarthritis of zygapophysial joints may affect
closely related spinal nerves, causing dermatomal pain and
myotomal spasm
NIGEL FONG 2011/2012
!
REG
Spine
MODE
MRI
COND
L5/S1 prolapse
PAGE A82
M1 NOTES IN GROSS ANATOMY
!
4 | BACK, SPINE & SPINAL CORD
!
!
Curvatures & Abnormalities
•
Thoracic & sacral kyphoses: concave anteriorly
•
- 1º curvatures dvp during fetal period
Cervical & lumbar lordoses: concave posteriorly
•
- 2º curvatures, result fr extension fr flexed fetal pos
Excessive thoracic kyphosis (“kyphosis”, hump/hunchback, Dowager’s hump):
•
- Abnormal ↑ thoracic curvature
- EG Osteoporosis forming short & wedge shaped thoracic vertebrae
- ↓ pulmonary capacity
Excessive lumbar lordosis (“lordosis”, hollow back, sway back):
•
- abnormal ↑ lumbar curvature
- May be temporary in pregnancy, obesity etc.
Scoliosis: abnormal lat curvature accompanied by rotation of vertebrae.
Neurovascular supply of the spine
•
•
•
Arterial supply: branches of maj segmental art
- Vertebral art in neck, pos intercostal art,
lumbar art, lat/med sacral art
Venous drainage: drain to maj segmental veins
- Forms
communicating
int
vertebral
(epidural) & ext vertebral venous plexus
Nerve supply: recurrent meningeal branches
arising directly from mixed spinal nerve (before
div into ant/pos rami), or from ant rami.
!
Muscles moving the spine
•
•
•
Extrinsic back muscles (e.g. trapezius, lat dorsi etc) connect to appendicular skeleton
Intrinsic back muscles (mainly erector spinae muscles)
- Maintain posture and extend the spine
- Supplied by pos rami spinal nerves
Interaction btw contralateral pairs of erector spinae, ant abdominal muscles produce
the full range of motion.
!
NIGEL FONG 2011/2012
PAGE A83
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
B. SUPPORT OF CRANIUM
!
Atlanto-occipital joint
•
•
•
Permit flexion & extension (as in nodding), some sideways tilting
Synovial condyloid jt btw sup articular surf of lat mass of atlas, and occipital condyles
Reinforced by ant/pos membranes
Atlanto-axial joint
•
•
•
Permits rotation of the head (e.g. saying “no”).
Synovial gliding jt: Rotation of lat mass of
atlas on articular facets of axis
Dens (odonthoid process) is a pivot abt which
rotation occurs
- Dens of ant axis projects superiorly fr body
- Held in a socket formed ant by ant arch of
atlas, pos by transverse lig of atlas
!
!
!
NIGEL FONG 2011/2012
PAGE A84
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
2. SPINAL CORD
!
A. EXTERNAL STRUCTURE
!
The spinal cord
•
•
•
!
Lower elongated part of the CNS, beginning as a continuation of the medulla.
31 spinal segments give rise to 31 spinal nerves:
- C1-C7 emerges sup to their corresp. vertebrae
- C8 emerges between C7 & T1, there are only 7 cervical vertebrae
- T1-Co emerge below their vertebrae
Cervical & lumbar enlargment: areas of higher neuron density, supplying limbs
Formation of the cauda equina
•
•
In embryos, spinal cord occupies full length of vertebral canal, but vertebral growth
outpaces spinal cord growth later.
Spinal cord extends only to L2 (var: T12-L3), ending as the conus medullaris
•
Caudal spinal nerves continue towards IV foramina lower than their levels of origin as
the cauda equina (“horse tail”)
•
Clinical: Lumbar puncture / epidural anesthesia: spinal cord can be accessed in midline
btw spinous processes, inf to L2 where there is no danger of damaging spinal cord
!!!!
NIGEL FONG 2011/2012
!
PAGE A85
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
B. SPINAL MENINGES
Meninges
•
•
Meninges of spinal cord are continuous with that of the brain, via the foramen magnum
Dura mater: tough fibrous tissue
•
- 1 layer only: ext periosteal layer of cranial dura does not extend into spinal cord
- SS by somatic meningeal nerves; responsible for referred pain e.g. meningitis
Arachnoid mater: delicate avascular membrane containing CSF
•
- Closely apposed to but not adherent to dura.
Pia mater: closely apposed to spinal cord (barely visible to unaided eye)
-
•
Inf to conus medularis, continues as filum terminale, anchoring the inf end of the
spinal cord & meninges to the coccyx
Arachnoid & pia are together known as the leptomeninges
!
!
!
Spaces
•
Epidural space btw dura and bone (cranial dura does not have this)
•
- Filled with loose connective tissue & int vertebral plexus
- Accessed for epidural anesthesia
Subdural space (dura-arachnoid interface) is normally absent but is a potential space
for subdural hematoma because the arachnoid is not adherent to dura
Subarachnoid (leptomeningeal) space: btw arachnoid & pia, containing CSF
•
Lumbar cistern: While spinal cord ends at L2, subarachnoid space (with CSF)
extends to S2, where it surrounds the cauda equina.
Lumbar puncture (spinal tap): Withdrawal of CSF from lumbar cistern by insertion
of needle in midline btw L3/L4 or L4/L5 allows diagnosis of CNS disorders
- Not performed if there is increased intracranial pressure, for fear of herniation of
the brain through the foramen magnum
-
•
NIGEL FONG 2011/2012
PAGE A86
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
C. VASCULATURE OF THE SPINAL CORD
!
Blood supply
•
•
1 ant spinal art & 2 pos spinal art, ext fr medulla of brainstem to conus medullaris
- Anastomosis supplied from vertebral art & segmental (radicular) arteries fr
arteries on wall of thorax, lumbar regions, etc
- Resillent supply that rarely occludes
Variable 3 ant & 3 pos spinal veins, extending longitudinally
- Communicates freely, joining int vertebral venous plexus in epidural space
-
Int vertebral plexus passes sup through foramen magnum to communicate with
dural sinuses
Also note communication btw prostatic plexus & int vertebral plexus (see pelvis &
perineum) as a route for spread of infection
!
!
NIGEL FONG 2011/2012
PAGE A87
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
D. SPINAL NERVES
!
!
Spinal cord
•
•
White matter (superficial) = bundles of axons (myelin appears white) forming
ascending/descending tracts
Gray matter (deep) = cell bodies organized in lamellae
-
•
Ventral horn: motor neurons
Dorsal horn: sensory neuron
Lateral horn: autonomic neurons (T1-L2 and S1-S2) =intemedio-lateral nucleus
Central canal: cerebro-spinal fluid (continuous with ventricles of brain)
Formation of spinal nerve
•
•
•
Dorsal root: Sensory neurons (both somatic and visceral) entering dorsal horn
- Contain dorsal root ganglia: cell bodies of sensory neurons
Ventral root: Motor neurons (somatic motor and visceral motor / autonomic) leaving
the ventral / lateral horn
Spinal nerve: Union of dorsal & ventral roots, contains both motor & sensory neurons
FIBRE
TYPE
CELL BODY
PATH
Sensory
Pseudo-unipolar
Dorsal root ganglion
Central process: dorsal root, dorsal horn
Peripheral process: to peripheral receptor
Ventral horn
Through ventral root to peripheral muscle
Preganglionic
Lateral horn
(intemedio-lateral nucleus)
Through ventral root & white comm. rami
Synapse with postganglionic neuron
Postganglionic
Autonomic ganglia
(paravertebral ganglia)
Through grey comm. rami to visceral
smooth muscle
Motor
Autonomic
[myelinated]
[non-mylienated]
NIGEL FONG 2011/2012
PAGE A88
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
Rami
•
•
•
Spinal nerve splits into ant & pos rami
Pos rami supply: deep back muscles, overlying
skin, and synovial joints of vertebral column
Ant rami supply everything else. Often merge
& split, forming somatic and visceral plexuses.
Reflex arc
•
Receptor respond to stimulus, sending impulse
to CNS via afferent sensory neuron
•
•
May synapse in CNS: integration
Efferent motor neuron carry
effector (e.g. muscle contract)
•
Reciprocal innervation of antagonist/agonist
muscle groups (e.g. tapping quadriceps tendon
results in hamstring contraction)
impulse
to
Dermatomes & Myotomes
•
•
•
Common dvpt from an embryological somite
Dermatome = area of skin innervated by a
single spinal nerve (significant overlap)
Myotome = muscle mass receiving innervation
by a single spinal nerve
!
Dermatomal map:
!!!!!!!!!!!!!!
NIGEL FONG 2011/2012
!
PAGE A89
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
3. AUTONOMIC NERVOUS SYSTEM
A. FUNCTION OF AUTONOMIC SYSTEM
!
Somatic & visceral parts of the body
•
•
Somatic part of the body (e.g. hands, legs) is under voluntary control (somatic motor)
& conscious sensation (somatic sensory)
Visceral part of the body (internal organs) are under involuntary regulation (somatic
motor, known as autonomic) and below conscious sensation (visceral sensory)
SENSORY
MOTOR
Somatic sensory [skin, joints]
= General somatic afferent
Somatic motor [skeletal muscle]
= General somatic efferent
Viscero sensory [internal organs]
[visceral reflex, visceral pain]
= General visceral afferent
Autonomic [smooth muscle, cardiac, glands]
= General visceral afferent
SOMATIC
VISCERAL
[subconscious,
homeostasis]
ENTERIC
Parasympathetic div
Sympathetic div
Enteric system: control GIT reflex, peristalsis, secretomotor activity, vascular tone.
CNS-independent but modified by CNS input
!
Divisions of the autonomic system
•
•
•
Parasympathetic system facilitates functions of bodily maintenance, e.g. digestion
- Major supply to viscera; limbs have no parasympathetic supply
- Exocrine secretory organs (e.g. saliva, pancreas) all stim. by parasympathetics,
except sweat glands
Sympathetic system prepares the body to deal with stress (‘fight or flight’)
- More diverse supply, not only to viscera
In the limbs: sympathetic motor fibres travel with cutaneous fibres, supplying
- Vasomotor: smooth muscles in blood vessels
- Pilomotor: arrector pili muscles in hair folicles
- Sudomotor: stimulation of sweat glands
!
(thoraco-lumbar outflow)
Catabolic
Fight
or
flight
Unnecessary blood vessels
constrict (e.g. peripheral),
important ones dilate (e.g.
cardiac blood supply)
!
!
!
NIGEL FONG 2011/2012
Sympathetic
Dilate
Increase
Increase
Dilate
Secrete
Hair stands
Decrease
Increase
Ejaculation
Para-sympathetic (cranio-sacral outflow)
EYE
HEART RATE
RESPIRATORY RATE
BRONCHI
SWEAT
Constrict
Decrease
Decrease
Constrict
-
Anabolic
Rest
&
repose
ARRECTOR PILI
DIGESTION
ADRENALINE
BLADDER
SEX ORGANS
Increase
Decrease
Contract
Erection
PAGE A90
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
B. AUTONOMIC NERVES
Principles
•
Sympathetic output = thoraco-lumbar outflow:
-
•
•
•
Comes from T1-L2 segments of the spinal cord only
Supplies entire body by going superiorly & inferiorly through sympathetic chains
Parasympathetic output = cranio-sacral outflow
- Comes from cranial n III, VII, IX, X (Vagus CN X has long course to SS viscera)
- Comes from S2-S4 segments
Unlike somatic motor, visceral motor (autonomic) requires 2 neurons to go from CNS
to target organs: presynaptic and postsynaptic neurons
- Presynaptic neuron is myelinated, postsynaptic is unmyelinated
- Sympathetic:
short presynaptic and long postsynaptic neuron
- Parasympathetic:
long presynaptic and short postsynaptic neuron
Visceral plexuses are a network of motor & sensory, sympathetic & parasympathetic
fibres
!
!
!
NIGEL FONG 2011/2012
PAGE A91
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
Autonomic (sympathetic) ganglia
•
•
•
Contain cell bodies of post-synaptic
sympathetic neurons
Pre-ganglionic neurons:
- Exit spinal cord through ventral root
(they are visceral motor neurons after
all) at T1-L2 levels
- Exit ant rami of spinal n thru white
rami
communicans
(preganglionic
fibres have myelin sheath, hence white)
!
- Enter autonomic ganglia and synapse on post-ganglionic neurons
Post-ganglionic neurons:
- Leave autonomic ganglia via grey rami communicans (postganglionic fibres are
unmyelinated, hence grey)
- Travel to target via spinal nerves
!
Formation of paravertebral sympathetic trunk
•
•
Autonomic ganglia connected sup & inf to form paravertebral sympathetic trunk
- Necessary because preganglionic sympathetic fibres exit the spinal cord from T1-L2
only, but sympathetic supply is needed at all levels.
- Pre-ganglionic neurons providing sympathetic supply to spinal nerves sup/inf to
T1-L2 travel in the sympathetic trunk and synapse onto the postsynaptic neurons
at the autonomic ganglia of the correct level.
Only T1-L2 have white rami communicans, but all levels have gray rami communicans
!
!
NIGEL FONG 2011/2012
!!!!!!!
!
PAGE A92
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
Splanchnic nerves
•
•
•
Splanchnic nerves = pre-ganglionic neurons that do not
synapse at the autonomic ganglia but pass through
without stopping
- Travel directly to prevertebral plexuses (e.g. aortic,
sup mesenteric etc)
- Post-ganglionic cell bodies located at prevertebral
plexuses
Supply certain viscera e.g. digestive system
All splanchnic nerves (greater, lesser, least etc) are
sympathetic except the pelvic splanchnic nerves which are
parasympathetic
Summary
VISCERO-MOTOR
PRESYNAPTIC
CELL BODY
!
POSTSYNAPTIC
PATH
CELL BODY
PATH
Ventral root, white
ramus
Paravertebral
ganglia (same level)
Gret rami, spinal
nerve (same level)
Paravertebral
ganglia (other level)
Grey rami, spinal
nerve (other level)
Sup cervical gangl.
Periarterial plexus
or cranial nerves
Prevertebral
ganglia ant to aorta
To GI tract
Adrenal medulla
Instead of
synapsing, release
neurotransmitter
into bloodstream
Ganglia in head
To eye/head glands
Near to or wall of
target organ
To viscera
Sympathetic:
Spinal nerve T1-L2
Spinal nerve C1-C8
L3-Co.
To head
Splanchnic nerves
to GI tract
T1-L2
spinal cord
lateral horn
Ascend/descend in
paravertebral chain
(sympathetic chain)
(intemedio-lat
nucleus)
Pass through sym.
trunk w/o synapse
Splanchnic nerves
to adrenal gland
Parasympathetic:
Cranial outflow
Brainstem
nuclei
Follow CN3/7/9/10
to head or viscera
Sacral outflow
S2-S4 lateral
horn
Colon (descending
& sigmoid), rectum
NIGEL FONG 2011/2012
PAGE A93
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
Neurotransmitters
•
•
•
Noradrenaline (adrenergic nerves):
Acetylcholine (cholinergic nerves):
Postganglionic sympathetic (except sweat glands)
All other fibres
postganglionic sympathetic fibres at sweat glands
Different receptors allow for different responses to one stimuli by different target cells
Noradrenaline receptor: α1
Widespread
Excitatory
α2
GIT
Inhibitory
β1
Heart
Excitatory
β2
Bronchi
Inhibitory
NIGEL FONG 2011/2012
PAGE A94
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
C. AFFERENT VISCERO-SENSORY NERVES
Nerves
•
!
!
Single nerve, unlike autonomic efferent
VISCERO-SENSORY
COURSE
CELL BODY
SENSATION
Visceral reflex
Follow parasympathetic
nerves i.e. CN9/10
Inferior ganglia of
CN9/10
Does not reach
consciousness
Visceral pain
Follow sympathetic fibres,
spinothalamic tract
Dorsal root ganglia
Pain, difficult to localise,
may be refered pain.
Referred pain
•
•
•
Pain may be perceived at a site adjacent to or at a distance
from the site of origin
Convergence theory: pain from viscera may be felt in the
dermatome of the somatic nerve converging onto the same
spinal segment, brain cannot differentiate source of pain.
EG: pain from appendicitis is referred onto the umbilicus
(T10 dermatome).
!
NIGEL FONG 2011/2012
PAGE A95
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
4. SPINAL PATHWAYS
!
*Collections of cell bodies in the | CNS = nucleus
| PNS = ganglia
*Bundles of neurons in the
| CNS = tract, fasciculus, peduncle, lemniscus | PNS = nerves
A. COMMON FEATURES
Decussation
•
•
All pathways except spinocerebellar decuss (cross midline)
- 1 side of body perceived and controlled by the opposite side of brain
Clinical implication: pathway of tract implies consequence (modality lost, ipsilateral or
contralateral) of tract interruption at a certain level
- Pt with spinal cord lesion may present with both ipsilateral (same side) and
contralateral (different side) loss of various functions, depending on where the
pathway for that function crosses the midline.
Organization
•
•
•
•
Somatotopic arrangement: tracts are wellorganized with fibres located according to their
destination/source
Medial lemniscus: in the medial lemniscus of the
medulla, anterior fibres go to the leg while
posterior fibres go to upper regions
Cortico-spinal tract: fibres terminating at the
rostral spinal cord travel more medially, fibres
terminating at the distal spinal cord travel
laterally.
The sensory and motor cortex are also organized
by the regions they serve. (right: somatosensory
homunculus shows this relationship)
!
!
NIGEL FONG 2011/2012
PAGE A96
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
B. PATHWAYS
!
!
!
!
NIGEL FONG 2011/2012
!
PAGE A97
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
Sensory (Ascending) pathways
•
•
•
•
1º neuron all in dorsal root ganglia
2º neuron location differs; this neuron decussates (except spinocerebellar)
3º neuron lies in thalamus and projects to somatosensory cortex (post-central gyrus)
Trigemino-thalamic system (CN V) operates on a similar principle
!
PATHWAY
MODALITY
2º NEURON
DECUSSATION
Spinothalamic
(antero-lateral sys)
Crude touch & pressure
Pain & temperature
Spinal cord, dorsal horn
In spinal cord, near
spinal nerve supplied
Dorsal column
medial lemniscus
Fine touch, vibration,
pressure, conscious
proprioception
Medulla: nucleus
- gracilis (lower body)
- cuneatus (upper body)
In the medulla
oblongata
Spinocerebellar
Unconsci proprioception:
coord mvmt, posture,
balance, muscle tone
Spinal cord, dorsal horn
(no 3º neuron)
Mostly uncrossed
Motor (Descending) pathways
•
•
Pyramidal tract is the most important motor pathway, controlling mainly flexors
Extrapyramidal tracts (postural pathways) influence muscle tone, posture, and
movement. They modify and influence the activities of the pyramidal system on LMN
!
TRACT
FUNCTION
ORIGIN
DECUSSATION
Cortico-spinal
(pyramidal)
Voluntary movement
Fr cerebral cortex, via
corona radiata, internal
capsule, cerebral peduncle,
pyramids of medulla
90%: Lat CST:
decuss at pyramids
10%: Ant CST:
decuss at spinal cord
Cortico-bulbar
Cranial nerve LMN
Cerebral cortex
Bilateral influence
usually (see CN VII)
Rubro-spinal
Excitatory to flexors,
unimportant
Midbrain, red nucleus
Cross
Tecto-spinal
Mediate reflex mvmt in
resp to visual stimuli
Midbrain, sup
(tectum)
Cross
Vestibulo-spinal
Control extensors for
posture and balance
Lat vestibular nucleus
Med vestibular nucleus
Uncross
Reticulo-spinal
Muscle tone, voluntary
movement
Pons & medulla: reticular
formation
Cross
Extra-pyramidal:
!
!
!
NIGEL FONG 2011/2012
PAGE A98
M1 NOTES IN GROSS ANATOMY
4 | BACK, SPINE & SPINAL CORD
C. UPPER & LOWER MOTOR NEURONS
!
Upper & Lower motor neurons
•
•
•
Upper motor neuron: CNS neurons loc in 1º motor cortex, brain, brainstem
- Source of descending pathways, influences LMN
Lower motor neuron: located in ventral horn of spinal cord or brainstem motor nuclei
- Directly synapse with ipsilateral skeletal muscles to stimulate contraction
Motor unit: single lower motor neuron + extrafusal fibres it synapses on
- Small motor units synapse on a few muscle fibres, large motor unit synapse on
many muscle fibres
Upper vs lower motor neuron lesion
•
•
Lower motor neuron lesion is clear: lose control of muscle
Upper motor neuron lesion affects contralateral side of body
- Initial hypotonia, hyporeflexia, flaccid paralysis
- Followed by chronic hyperreflexia & spasticity
!
SIGN
Tone
LMN LESION
UMN LESION
Flaccid paralysis
Spastic paralysis
Atrophy
Yes
No
Fasiculations
Yes
No
Tendon reflex
↓
↑
No
Yes
↓ or absent
Extensor reflex
(Babinski’s sign)
Clonus
Plantar reflex
NIGEL FONG 2011/2012
NOTES
Errors: cold, stress, anxiety, meds
Pull ankle up, ankle ‘shivers’.
Up to 3 beats of clonus acceptable
Stroke sole of foot
Normal: flexor plantar reflex
PAGE A99
M1 NOTES IN GROSS ANATOMY
5 | THORAX
CHAPTER 5: NORMAL STRUCTURE AND DEVELOPMENT OF THE
5 | THORAX
!
!
1. THORACIC WALL
!
A. BONES OF THORACIC WALL
Thoracic vertebrae
•
•
•
Long, inferiorly slanting spinous process
Superior & inferior costal demifacets on vertebral bodies for articulation with ribs
Costal facets on transverse process (except T9-12)
Sternum
•
•
•
•
Manubrium, body, & xiphoid process connected by cartilagenous joints (synchondroses)
that ossify in adulthood
Palpable jugular notch near sternoclavicular joint
Palpable sternal angle (of Louis) btw manubrium and sternal body corresponds to
Rib 2 and T4 vertebrae. This relation is used to count ribs
Xiphoid process marks the central tendon of diaphragm, inferior border of heart, and
superior limit of liver.
!
NIGEL FONG 2011/2012
PAGE A100
M1 NOTES IN GROSS ANATOMY
5 | THORAX
!
Ribs
•
•
•
•
•
•
•
•
•
•
Slope inferiorly
True (vertebrocostal) ribs 1-7
: attach to sternum directly through costal cartilages
False (vertebrocondral) ribs 8-10 : attach to cartilage of rib above them
Floating (vertebral) ribs 11-12
: do not connect with sternum
Costal cartilage & joints provides flexibility, absorbing forces without fracture
Contain bone marrow (even in adult)
Typical ribs 3-9: costal angle is where the rib turns sharply
Atypical rib 1: flat, short, sharply curved, has scalene tubercle for anterior scalene
muscle, and grooves for subclavian vein (anterior) and subclavian artery (posterior)
Atypical rib 11-12: Short, no neck or tubercle
11 intercostal spaces are named after the rib above them.
!
NIGEL FONG 2011/2012
!
!
PAGE A101
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Clinical notes
•
•
•
•
•
•
•
Supernumerary ribs: cervical or lumbar ribs may form, or the 12th rib may not form.
This confuses the identification of vertebral levels
1st rib is not palpable
Relation of sternal angle to 2nd rib is used to count ribs
Costal cartilages are very visible when calcified in old age
Rib fractures are painful as they move during respiration
Sternal fractures are uncommon but suggest underlying mediastinal injury
Thoracotomy: surgical opening of thoracic wall by H-shaped incision of periosteum,
strippage of periosteum and removal of rib. The thoracic cavity can be entered through
the periosteal sheath (avoiding the intercostals). Regernation of ribs is possible from
the periosteum.
!
B. THORACIC INLET & OUTLET
Superior aperture (anatomical thoracic inlet, clinical thoracic outlet)
•
•
•
Oblique, kidney-shaped
Bounded by T1 vertebra, 1st ribs (not palpable) and cartilages, and superior border of
manubrium of sternum
Structures: trachea, esophagus, nerves and vesseles that supply the head, neck, and
upper limbs.
Inferior aperture (anatomical thoracic outlet)
• Bounded by T12 vertebra, ribs 11-12, costal margin formed by joined costal cartilages
•
of ribs 7-10, and xiphisternal joint
Diaphragm forms border between thoracic and abdominal cavities. It is also the
primary muscle of respiration.
!
NIGEL FONG 2011/2012
PAGE A102
M1 NOTES IN GROSS ANATOMY
5 | THORAX
C. JOINTS OF THORACIC WALL
!
Costovertebral
•
•
•
•
•
•
Superior facet on head of rib articulates with inf demifacet of the vertebra above it
Inferior facet on head of rib articulates with sup demifacet of same numbered vertebra
Crest of head of rib (between the facets) attaches to intervertebral disc by intraarticular ligament of head of rib
Ribs 10-12 articulate only with a single vertebra and have only 1 facet
Ribs 11-12 have no tubercle and do not articulate with transverse process
Radiate ligament of head of rib forms anteriorly
Costotransverse joints
•
•
•
•
Costotransverse jt: Tubercle of rib attaches to transverse process of same-no vertebra
Sup costotransverse ligament joins neck of rib to transverse process of sup vertebra
Lat costotransverse ligament passes from tubercle of rib to tip of transverse process
Spinal nerves and pos branch of intercostal artery exit between aperture formed by sup
costotransverse ligament and vertebra body
Other joints
!
JOINT
TYPE
LIGAMENTS & CARTILAGE
MOVEMENT
Intervertebral
Symphysis
Intervertebral discs (fibrocartilage)
Ant & pos longitudinal
Rotation
Costochondral (rib & cartilage)
Cartilaginous
Periosteum binds cartilage and bone
-
Sternocostal
Synovial plane
Ant, pos, radiate sternocostal
-
Interchondral (false ribs)
Synovial plane
Interchondral ligaments
-
!
!
NIGEL FONG 2011/2012
PAGE A103
M1 NOTES IN GROSS ANATOMY
5 | THORAX
D. MUSCLES & MOVEMENTS OF THORACIC WALL
!
Movements
•
•
•
•
Movements of thoracic wall & diaphragm,
change the intrathoracic pressure and volume
for inspiration and expiration.
Diaphragm contraction increases vertical
dimension of thorax
Pump-handle movement: rotation of upper ribs
at costovertebral joints causes the anterior
ends of the rib cage and sternum to rise and
move outwards, increasing the anteriorposterior diameter of the thorax
Bucket-handle movment: outward movement
of lateral-most parts of middle ribs increases
the transverse dimension of the thorax.
!
Intercostal muscles
•
•
•
•
•
•
3 layers of muscles form in the 11 intercostal spaces, with the neurovascular bundles
between the internal and innermost intercostals.
External intercostals (11) slope inferoanteriorally. Anterior to the costochondral
junctions, external intercostals are replaced by the external intercostal membrane.
Internal intercostals (11) slope inferoposteriorly. Posterior to the angle of the ribs,
internal intercostals are replaced by internal intercostal membranes.
Innermost intercostals (11) are functionally similar to the internal intercostals.
Other muscles (unimportant): transversus thoracic, subcostal, serratus posterior
These support the intercostal space, preventing incursion of thoracic wall in inspiration
!
!
!
!
Respiratory muscle movements
•
•
•
•
Normal inspiration: diaphragm & external intercostals contract
Forced inspiration: scalene muscles, pectorals, serratus ant help elevate ribcage
Normal expiration: passive recoil of lungs & relaxation of diaphragm
Forced expiration: Internal intercostals, abdominals contract
NIGEL FONG 2011/2012
PAGE A104
M1 NOTES IN GROSS ANATOMY
5 | THORAX
E. NERVE SUPPLY OF THORACIC WALL
!
Intercostal nerves
ORIGIN
COURSE
TERM
BRANCH
SS
Motor
Sensory
CLINICAL
ATYPICAL
Anterior ramus of spinal nerve T1-T11
Ant ramus T12 = subcostal nerve
T1 branch also forms brachial plexus
Initially runs in fascia btw parietal pleura
and internal intercostal membrane.
Near angles of ribs, pass btw internal and
innermost intercostals inferior to lie in
costal groove of rib (inf to art & vein)
1st & 2nd course on int surf of ribs, instead
of costal groove
Near sternum, pierces muscle & turns
anteriorly to become anterior cutaneous
branch (divides into med & lat br)
Thoracoabdominal n: 7-11th intercostal
n continue to supply ant. abdominal wall.
Collateral branches arise near angle of ribs
and run along superior border of rib below
Lat cutaneous branch (div into ant & pos
br) arise at midaxillary line
Intercostobrachial n: fr 2nd intercostal n
enters and supplies the axilla, commu.
with med brachial cut. N to supply med &
pos arm.
Muscles in intercostal space: Intercostal, subcostals, transverse thoracis etc
Dermatome of trunk from pos med line to ant med line
Herpes zoster (shingles) infection of spinal ganglia appears as redness, burning pain, and
vesicular eruptions in dermatome supplied by affected nerve. Also see chest tube.
!
NIGEL FONG 2011/2012
PAGE A105
M1 NOTES IN GROSS ANATOMY
5 | THORAX
E. BLOOD SUPPLY OF THORACIC WALL
Internal thoracic (mammary) artery
ORIGIN
COURSE
TERM
BRANCH
CLINICAL
ORIGIN
COURSE
Root of neck, first part of subclavian art.
Descend into thorax pos. to clavicle and 1st costal cartilage.
Crossed at origin by ipsilateral phrenic nerve
Descend on int surf of thorax, pos to costal cartilage 1-6 & intercostal muscles, slightly
lat. to sternum
At 6th intercostal space, divide into sup. epigastric & musculophrenic art.
Gives 1st 6 ant. intercostal arteries.
Pericardiophrenic art: supply pericardium
Provides collateral circulation to abdomen in case of blockage of descending aorta
Sometimes used for coronary artery bypass grafts
Pos intercostal arteries (11)
1-2: sup. intercostal art (fr subclavian)
3-11: fr thoracic aorta
Ant intercostal arteries (9)
1-6: Internal thoracic (mammary) art
7-9: Musculophrenic art.
With intercostal n. through intercostal
spaces, enter costal groove at costal angle
In costal groove on inf border of rib: sup to intercostal n, inf to intercostal vein.
TERM
BRANCH
CLINICAL
Ant & pos anastomose with each other
Pos. br: follows pos ramus of spinal n
Collateral br: sup border of rib below
To pectoral muscles, breasts, skin
Collateral br: sup border of rib below
See chest tube
NIGEL FONG 2011/2012
PAGE A106
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Venous drainage of thoracic wall
•
•
•
•
Intercostal veins accompany intercostal arteries in the costal groove and lie sup. to
intercostal art & nerve
Drain into internal thoracic veins are venae comitantes internal thoracic artery
(internal thoracic vein drains into brachiocephalic vein)
Drain also into azygos venous system
Lymphatics – see mediastinum
F. NEUROVASCULAR RELATIONS IN THE INTERCOSTAL SPACE
The intercostal space
•
Lie in vascular plane between internal & innermost intercostals
•
Main neurovascular bundle runs in the costal groove on the inferior border of the rib.
Order of structures is: [superior] vein-artery-nerve [inferior]
•
Collateral branches run on the superior border of the rib. Order of structures is
[superior] nerve-artery-vein [inferior]
NIGEL FONG 2011/2012
PAGE A107
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Clinical: Chest tube insertion
•
•
•
•
•
Chest tubes may be inserted for drainage of pneumothorax (see later)
Insert at midaxillary line of 4th intercostal space to avoid liver on the right, and
the spleen, heart, and stomach on the left
- Triangle of safety formed btw lat dorsi, pec maj, and 6th rib
- Slightly off the mid axillary line to avoid damaging the long thoracic nerve
Keep needle close to upper border of rib to protect neurovascular structures in the
subcostal groove.
In tension pneumothorax, needle is inserted at the midclavicular line, 2nd intercostal
space as that is more accessible
Thoracentesis: hypodermic needle to sample pleural fluid may be inserted angled
upward in 9th intercostal space, midaxillary line to avoid penetrating the diaphragm
G. CONTENTS OF THORAX
Regions
•
•
•
•
!
Contains 2 pulmonary cavities (with lungs) and the mediastinium between them
Superior mediastinum: sup to transverse thoracic plane, fr sternal angle (T4/T5
intervertebral disc)
Heart and root of great vessels occupies middle mediastinum, dividing the inferior
mediastinum into anterior and posterior parts
Heart located slightly to the left (about 2/3s on the left)
!
NIGEL FONG 2011/2012
PAGE A108
M1 NOTES IN GROSS ANATOMY
5 | THORAX
2. LUNGS & PLEURAE
A. INTERNAL ANATOMY
!
Pleurae
•
Pleurae fill left and right pulmonary cavities and line the lung
The parietal (sup) and visceral pleura (deep) are continuous ( like a fist punched
into balloon”) and reflect onto each other at sternal, costal, and vertebral lines.
Continuity between parietal and visceral pleura forms pulmonary ligament
•
•
•
•
Parietal pleura: cervical (cupula), mediastinal, costal, and diaphragmatic parts
Visceral pleura is adherent to lung surfaces (cannot be dissected)
Pleural cavity is a potential space and contains a capillary layer of pleural fluid
Pleural fluid lubricates the pleural layers, allowing sliding as the lung inflates/deflates
•
•
- Clinical: Pleural effusion – excessive accumulation of pleural fluid
•
Surface tension of the pleural fluid allows cohesion the lung surface to the thoracic
cage, so thoracic expansion translates into lung expansion.
Pleural recesses
•
•
•
Lungs do not fully occupy pulmonary cavities during expiration, so recesses form
(diagram: see surface anat). These allow for expansion of the lung during inspiration
Costodiaphragmatic recess: where diaphragmatic pleura contacts inf costal pleura
Costomediastinal recesses: where costal pleura contacts mediastinal pleura. Left recess
larger because the left cardiac notch is pronounced
Bronchial tree
•
•
•
•
•
•
•
•
Trachea forms fr larynx (C6) and is supported by C-shaped rings of hyaline cartilage
At sternal angle, trachea bifurcates into right & left main bronchi (primary bronchi)
The carina forms between the left & right main bronchi; it is very sensitive for
triggering a cough reflex
Clinical: Right main bronchus is shorter and more vertical, so foreign objects aspirated
into the lung are more likely to enter the right main bronchus
Primary bronchi divide into secondary (lobar) bronchi, each supplying a lobe
Lobar bronchi divide into tertiary segmental bronchi
Further division into conducting bronchioles, terminal bronchioles, respiratory
bronchooles, alveolar ducts, and alveoli (see histology)
Clinical: Bronchoscopy permits viewing of tracheobronchial tree
NIGEL FONG 2011/2012
PAGE A109
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Bronchopulmonary segments
•
•
•
•
= 18-20 pyramidal-shaped subdivisions of a lobe, with apices facing the root of the lung
and bases at the pleural surface
Supplied independently by segmental bronchi and a tertiary br of the pulmonary artery
Clinical: Surgically resectable; tumours localize in 1 bronchopulmonary segment
Clinical: Accumulation of carbon particles & soot (from urban pollution or smoking)
can turn alveoli black, usually without consequence.
Lungs
•
•
•
•
•
•
•
Apex extends into the root of the neck, base rests on the diaphragm
3 surfaces (costal, mediastinal, diaphragmatic), 3 borders (ant, inf, pos)
Right lung is divided into 3 lobes (sup, middle, inf) by oblique and horizontal fissures
Left lung is divided into 2 lobes (sup, inf) by an oblique fissure
Left lung has a deep cardia notch and a lingula.
Structures forming the root of the lung (see diagram) pass through the hilum and
attach the lung to the mediastinum
Cadaveric lungs leave impressions formed by adjacent structures (note relations)
!
NIGEL FONG 2011/2012
PAGE A110
M1 NOTES IN GROSS ANATOMY
5 | THORAX
B. SURFACE ANATOMY
!!!!!!!!
!!!
Surface markings of lungs & parietal pleurae
LEFT P PLEURA
APEX
RIGHT P PLEURA
Extends through sup thoracic aperture into
supraclavicular fossa
Apex 2-3cm sup. to junction of med & int 1/3 of clavicle
RIB 2
Pos. to sternoclavicular jt at midline of sternum
RIB 4
Descends in ant med line and starts
to deviate laterally
RIB 6
Lateral deviation for cardiac notch
Descends in ant
med line until
xiphisternal joint
RIB 8
Cross midclavicular line
RIB 10
Cross midaxillary line
RIB 12
Adjacent to vertebral column
LUNGS
Same borders as pleura
until rib 4
2 ribs
above
Midclavicular line
Midaxillary line
Adj to vertebrae
!
Surface markings of fissures
•
•
Oblique fissure: fr T2 vertebrae
inferioanteriorly to 6th costochondral junction
Horizontal fissure (R lung): from
4th costal cartilage, meets oblique
fissure in midaxillary line.
Areas of auscultation
•
•
•
Upper lobe – front of chest
Lower lobe – Back, below scapula
All lobes – at the midaxillary line
NIGEL FONG 2011/2012
PAGE A111
M1 NOTES IN GROSS ANATOMY
5 | THORAX
C. PULMONARY VESSELS
Pulmonary blood supply
•
•
•
•
!
2 pulmonary arteries (left, right) carrying deoxygenated blood arise from pulmonary
trunk at the sternal angle, and divide into lobar arteries, tertiary segmential arteries…
Gas exchange occurs in capillary beds of alveoli (see histology)
4 pulmonary veins (sup & inf on each side) return oxygenated blood to the left atrium.
Right middle lobe vein is a tributary of right superior pulmonary vein.
Clinical: pulmonary embolism – see physiology
Pulmonary lymphatics
•
•
•
•
Tracheobronchial nodes surround the roots of lobar & main bronchi, and tracheal sides
Efferent vessels from these nodes unite with vessels from parasternal and
brachiocephalic nodes to form right and left bronchiomediastinal trunks
Bronchiomediastinal trunks drain into junction of subclavian & internal jugular vein,
together with thoracic duct for RHS
Clinical: Lung carcinoma tends to result in swelling supraclavicular nodes (sentinel
node) and may affect a phrenic nerve, resulting in paralysis of the diaphragm.
!
!
NIGEL FONG 2011/2012
PAGE A112
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Bronchial vessels
•
•
•
•
In addition to pulmonary vessels, small bronchial arteries (oxygenated blood) enter the
lung to provide nutrition of the structures making up the root of the lungs and the
visceral pleura
Bronchial veins drain directly into the left atrium instead of the right atrium, forming
a physiologic shunt and diluting the oxygenated blood of the aorta.
Pulmonary vessels = pulmonary circulation, carry deoxygenated blood to lungs
Bronchial vessels = systemic circulation (hence bronchial artery = oxygenated)
!
!
D. PULMONARY NERVE SUPPLY
Pleurae
•
•
•
•
Parietal pleura is supplied by nerves & vessels that supply the cutaneous layer
Clinical: Pain from parietal pleura may be local or referred to same spinal dermatome
Visceral pleura is supplied by nerves & vessels that supply the viscera.
Clinical: Pain from visceral pleura may be referred to C3-5 (shoulder & root of neck)
!
Autonomic nervous supply to lungs
SYMPATHETIC
PARASYMPATHETIC
NOTES
PATHWAY
From sympathetic trunks
(paraverterbral ganglia)
From vagus n, synapse in
parasympathetic ganglia
of pulmonary plexus
Pulmonary plexus
forms around (mainly
pos to) root of lungs
NEUROTRA
Norepinephrine
Acetylcholine
SMOOTH
MUSCLE
Bronchodilator (inhibit
parasympathetic impulse)
Bronchoconstrictor
Unusual response:
Dilation = more resp.
in fight-or-flight
PULMON
VESSELS
Vasoconstrictor
Vasodilator (inhibit
sympathetic signal)
Like in rest of body
TYPE 2
CELLS
Inhibitory
Secretomotor
(secrete surfatant)
Secretion of surfactant
performed during rest
& maintenance state
NIGEL FONG 2011/2012
PAGE A113
M1 NOTES IN GROSS ANATOMY
5 | THORAX
E. RADIOGRAPHICAL ANATOMY & PATHOLOGIES
!
!
!
CXR Ref: http://www.meddean.luc.edu/lumen/MedEd/medicine/pulmonar/cxr/atlas/cxratlas_f.htm
Normal Chest X-ray
Pneumothorax
REG
Chest
MODE
X-ray P-A
COND
Normal
VIS
L: Lung
R: Rib
T: Trachea
AK: Aortic knob
A: Ascending aorta
H: Heart (on LHS)
P: Pulmonary artery
S: Spleen
Li: Liver
(breast shadows may be vis)
NOTE
Lung: with vascular lines
extending to periphery
Heart: cardio/thoracic ratio
> 0.55 (transverse diameters)
REG
Chest
MODE
X-ray P-A
COND
Pneumothorax in R lung
VIS
Collapsed lung (atelectatic)
Air appears black
No vascular markings
Deep sulcus (larger
costodiaphragmatic recess)
Increased haziness on L lung
due to diversion of entire
cardiac output
NOTE
Pneumothorax = entry of
air into pleural cavity, eg
stab wound or rib fracture
Hydrothorax = entry of
water, e.g. fr pleural effusion
Hemothorax = blood, e.g.
from injury to major vessel
(hemo/hydro: fluid meniscus
vis at air/water interface)
NIGEL FONG 2011/2012
PAGE A114
M1 NOTES IN GROSS ANATOMY
Tension pneumothorax
5 | THORAX
REG
Chest
MODE
X-ray P-A
COND
Tension pneumothorax of R
lung. Clinical emergency.
VIS
As per pneumothorax.
Mediastinum shifted to left
NOTE
Tension pneumothorax may
form when the punctured
skin & fascia forms a oneway valve, allowing air in but
not out, such that thoracic
pressure increases and
compresses mediastinal
structures and affecting
cardiovascular function.
(see physio)
Tension pneumothorax is a
clinical diagnosis: trachea
shifted to side, elevated JVP
Atelectasis
REG
Chest
MODE
X-ray P-A
COND
Atelectasis R lung
VIS
Defn: loss of air in alveoli
Collapse of R lung (dense)
NOTE
Pneumothorax features
atelectasis but they are not
synonymous
Multiple causes eg
• airways are obstructed,
blood flow continues and
absorbs all O2 & N2
• Loss of surfactant
• Loss of –ve pleural
pressure
!
!
NIGEL FONG 2011/2012
PAGE A115
M1 NOTES IN GROSS ANATOMY
Pneumonia
5 | THORAX
REG
Chest
MODE
X-ray P-A
COND
Right upper lobe
consolidation due to
pneumonia
VIS
Density in right upper lobe.
Transverse fissure not shifted
NOTE
Histology: will see alveolar
spaces filled with
inflammatory infiltrate
Underlying lung architecture
may be preserved after
complete resolution
!
Edema
REG
Chest
MODE
X-ray P-A
COND
Pulmonary edema (fluid in
lungs)
VIS
• Enlarged heart
• Blood diverted to upper
lobes: thick vascular lines
(lower
zone
alveolar
hypoxia causes arteriolar
vasoconst)
• Interstit./alveolar edema
• Bilateral pleural effusions
(fluid in pleural space)
• Loss of sharp costodiaphragmatic recess
NOTE
Pleural effusion only gives a
clearer air/fluid level
!
NIGEL FONG 2011/2012
PAGE A116
M1 NOTES IN GROSS ANATOMY
Hyperinflated chest
5 | THORAX
REG
Chest
MODE
X-ray P-A
COND
Hyperinflated chest, e.g. due
to COPD
VIS
Ribs very horizontal
(increased A-P diameter)
10 ribs visible (normal: 8-9)
NOTE
1st rib is short and sharply
curving downwards
Looking at posterior portion
of ribs (ant portion is
cartilage, radiolucent)
NIGEL FONG 2011/2012
PAGE A117
M1 NOTES IN GROSS ANATOMY
5 | THORAX
3. DEVELOPMENT OF THE RESPIRATORY SYSTEM
!
A. BRONCHI & LUNGS
!
Lung bud
•
•
•
•
•
!
Respiratory diverticulum (lung bud) develops from the ventral wall of the foregut in
the 4th week.
Proximal part gives rise to larynx, distal end gives rise to the tracheal bud.
Sucessive division of the respiratory bud forms the main bronchi, lobar bronchi,
tertiary bronchi, bronchioles, then alveoli
Hence respiratory epithelium arises from endoderm of the gut.
Cartilage, smooth muscle, and connective tissue of the respiratory tract develop from
surrounding splanchnic mesenchyme (mesoderm).
Tracheo-esophageal septum
•
•
•
•
Tracheo-esophageal folds/ridges develop in the laryngotracheal diverticulum, approach
each other, and fuse to form the tracheo-esophageal septum
Tracheoesophageal septum divides the foregut into the ventral laryngotracheal tube
and the dorsal esophagus.
Clinical: a tracheoesophageal fistula arises due to
incomplete fusion of the tracheophageal folds and hence
incomplete division of the foregut into respiratory and
esophageal parts
Clinical: esophageal atresia occurs when a tracheoesophageal
fistula forms such that the superior part of the esophagus ends
blindly and the inferior part joins the trachea near its
bifurcation.
!
!
Maturation of the lungs
•
•
•
Lungs remain collapsed until birth and mature alveoli may not form until after birth
Type 2 pneumocytes only mature and produce surfactant towards the end of pregnancy
Respiratory distress syndrome: premature infants often lack sufficient surfactant
for adequate lung inflation. Maternal glucocorticoid treatment is routine to prevent
RDS in preterm labour.
!
NIGEL FONG 2011/2012
PAGE A118
M1 NOTES IN GROSS ANATOMY
5 | THORAX
B. DIAPHRAGM
!
!!!!
!
Embryological components
•
•
•
•
•
Diaphragm develops from mesoderm
Central tendon of diaphragm: Forms from septum transversum (mesoderm) which
forms cranial to the pericardial cavity and later lies between the pericardial and
abdominal cavities after cephalocaudal folding.
Right/left crus (muscle): Dorsal mesentry of esophagus (connects gut to back)
Musculature: Develops from somites C3-C5
Pleuroperitonial membranes: close the left & right pleuroperitonial canal, forming the
connective tissue around the central tendon. These form large portions of the early
fetal diaphragm but only small portions of the newborn diaphragm
Positional changes
•
•
•
During cephalocaudal folding, septum transversum (together with primordial heart)
migrates from C3-5 levels into the thorax
This is accentuated by rapid growth of the dorsal part of the embryo’s body
Phrenic nerves supplying the diaphragm arise from C3-5 (original location of
diaphragm) and elongate as the diaphragm descends.
Congenital diaphragmatic hernia
•
•
•
Arises in failure in closure of the pleuroperitonial canal (usually LHS)
Abdominal contents herniate into the thorax and compress the lung
Result in respiratory difficulty, absent breath sounds on the affected side, and impaired
thoracic movements
NIGEL FONG 2011/2012
PAGE A119
M1 NOTES IN GROSS ANATOMY
5 | THORAX
4. HEART
A. PERICARDIUM
•
•
!
Mediastinum covered by mediastinal pleura, able to accommodate movement, volume,
and pressure changes
Pericardium is a fibroserous membrane covering heart & root of gt vessels, deep to
mediastinal pleura
Fibrous pericardium
•
•
Fibrous pericardium forms superficial layer, cont with tunica adventicia of great vessels
Continuous w central tendon of diaphragm, forming pericardiophrenic ligament
•
Attached to sternum via sternopericardial ligaments
Serous pericardium
•
•
•
•
Serous pericardium forms parietal (superficial) and visceral (deep) layers, reflected
onto each other at the great vessels.
Serous pericardium = mesothelium (simple squamous epithelium)
Visceral layer of serous pericardium is also epicardium
Pericardial cavity between parietal and visceral layer contains pericardial fluid,
enabling frictionless movement & beating of the heart.
Pericardial sinuses
•
•
•
Form as a result of reflection of serous pericardium around great vessels
Transverse sinus: On sup. surf of heart, pos to aorta & pulmonary artery, ant to
pulmonary veins. Clinical: allows ligation of pulmonary trunk & asc aorta during surg
Oblique sinus: Pos to base, between pulmonary veins & inf vena cava. Can be
entered inferiorly.
NIGEL FONG 2011/2012
PAGE A120
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Neurovascular supply of pericardium
•
•
•
Arterial supply: Pericardiophrenic artery (br of int. thoracic artery)
Venous drainage: Pericardiophrenic v (drain into int thoracic v) & br of azygos veins
Nerves: Phrenic n (sensory), Vagus n (func uncertain), Sympathetic trunk (vasomotor)
Clinical notes
•
•
•
•
•
•
Pericarditis: pericardial inflammation, causing chest pain & pericardial friction rub
Pericardial effusion: fluid in pericardial cavity (eg from capillaries).
Pneumopericardium: in pneumothorax pt, air may enter allong connective tissue
Hemopericardium: blood in the pericardial cavity (eg from stab wound)
Cardiac tamponade (Emergency): Compression of heart, due to extensive pericardial
effusion and the inability of the tough & elastic fibrous pericardium to accommodate
greater volumes. Characterised by hypotension, tachycardia, muffled heart sounds, and
jugular venous distension, eventually causing cardiogenic circulatory shock.
Pericardiocentesis: Drainage of fluid from pericardial cavity through needle insertion
at left 5th/6th intercostal space near sternum
B. EXTERNAL STRUCTURE OF HEART
!
Macro structure
•
•
•
•
•
•
•
Size: about the size of a clenched fist
Shape: pyramidal / trapezoidal
Apex: At anterior left 5th intercostal space, formed by inferolat of left ventricle.
Remains motionless throughout the cardiac cycle
Base: Pos aspect of heart, formed by left atrium
Surfaces: ant/sternocostal (RV), inf/diaphragmatic (LV/RV), right pulmonary (RA),
left pulmonary (LV)
Borders: right (RA, between vena cavae), inf (RV/LV), left (LV), sup (RA/LA)
Clinical: blunt trauma to sternum most likely to injure RV
!
NIGEL FONG 2011/2012
!!
!
PAGE A121
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Walls
•
•
•
•
•
Layers: epicardium (visceral layer serous pericardium), myocardium, endocardium
Pulmonary circulation: right atrium & ventricle receive venous blood from superior &
inferior vena cava and pump it through the pulmonary trunk & arteries to lungs
Systemic circulation: left atrium & ventricle receive oxygenated blood from 4
pulmonary veins, and pump it into the aorta
Coronary sulcus (AV groove): demarcates atria from ventricles. Corresponds deeply to
the AV orifice
Interventricular sulci/groove (ant & pos): separate right and left ventricle. Corresponds
deeply to the IV septum, which has a muscular part and a membranous part
!
Fibrous skeleton
•
•
•
•
!
4 fibrous rings surround orifices of valves,
providing attachment for valve cusps, and
preventing over-distension of the orifices
R/L fibrous trigone (between rings) provide
attachment fo the myocardium
Form membranous parts of the interatrial &
interventricular skeleton
Forms an electrical insulator between the
atria & ventricles to allow independent
contraction, timed by the AV node.
!
Imaging modalities
•
•
•
•
•
•
•
Chest X-ray: assess lungs & cardiomegaly
Echocardiography: baseline modality after ECG
CT scan: questionable
Cardiac MRI: Gold standard to access cardiac function.
Views available: 4-chamber, 2-chamber, left ventricular outflow tract etc
Angiography: where acute myocardial infarction is clear, patient sent straight to
catheter lab for angiography, which allows localization of the block and immediate
intervention (e.g. stenting)
Nuclear medicine studies look at viability of heart (e.g. recovery aft myocardial infarc)
NIGEL FONG 2011/2012
REG
Chest
MODE
CT P-A
COND
Normal
VIS
Ascending aorta
R to L: RA, RV, LV
NOTE
LA is most posterior and
tends to be damaged in blunt
chest trauma
PAGE A122
M1 NOTES IN GROSS ANATOMY
5 | THORAX
!
REG
Chest
MODE
X-ray P-A
COND
Dextrocardia situs inversus
VIS
Mediastinum on right instead
of left.
Lungs normal
Gastric bubble on RHS
NOTE
Dextrocardia situs inversus:
great vessels usually
positioned in mirror immage.
Isolated dextrocardia
affecting only the heart is
complicated by transposition
of the great arteries.
Also check for radiographer
error in labelling R/L
!
C. CHAMBERS OF HEART
!
Key features
!
RIGHT ATRIUM
LEFT ATRIUM
RIGHT VENTRICLE
LEFT VENTRICLE
LOCATION
Right border
Base of heart
Ant surf, inf border
Apex, pulmonary /
diaphragmatic surf
INLET
Vena cavae (sup/inf)
Coronary sinus
4 pulmonary
veins
R AV orifice
Tricuspid valve
L AV orifice
Mitral valve
(bicuspid valve)
OUTLET
R AV orifice
Tricuspid valve
L AV orifice
Mitral valve
(bicuspid valve)
Pulmonary trunk
2 pulmonary arteries
Pulmonary valve
Aorta
Aortic valve
3
Pectinate muscles
L/R auricle is muscular
MUSCLES
WALL
Ant wall rough
Pos wall smooth
Sep by sulcus (ext) /
crista (int) terminalis
NOTES
Oval fossa (R) / floor of oval fossa (L)
in interatrial septum is remnant of fetal
foramen ovale
Smooth & rough
-walled parts
papillary muscles w cordae tendinae
2
Trabeculae carnae (muscular elevations)
Moderator band
(Septomarginal trabecula)
Sup: conus arteriosus
(infundibulum)
Supraventricular crest
helps bloodflow U-turn
Smooth-walled
aortic vestibule
leads to the aorta
Walls 3x as thick as
RV
!
NIGEL FONG 2011/2012
PAGE A123
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Right atrium
Right ventricle
!
NIGEL FONG 2011/2012
!
PAGE A124
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Left atrium
!
Left ventricle
Clinical notes
•
•
L/R ventricular hypertrophy results when the heart is forced to worked harder e.g. in
aortic valve stenosis
Atrial / ventricular septal defect: see embryology
NIGEL FONG 2011/2012
PAGE A125
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Imaging & Clinical notes
REG
Heart
MODE
MRI 4-chamber view
COND
Normal
VIS
Observe 4 chambers of heart
with RV most ant, and LV
forming apex.
Crista terminalis of RA
visible
NOTE
REG
Chest & Heart
MODE
MRI with contrast
COND
Myocardial infarction of LV
VIS
Black LV: alive
White LV: dead
NOTE
Recommend against coronary
artery bypass graft, since
myocytes are already dead
REG
Heart
MODE
MRI 4-chamber view
COND
LV Hypertrophy
VIS
Thick LV myocardium
NOTE
Adaptation to pressure
overload, secondary to
systemic hypertension, aortic
valve stenosis, or coarctation.
Eventual fibrosis of
myocardium may result in
sudden cardiac death
!
NIGEL FONG 2011/2012
PAGE A126
M1 NOTES IN GROSS ANATOMY
5 | THORAX
REG
Heart
MODE
MRI 4-chamber view
Orientation: note image has
spine on the back.
COND
LV Dilatation
VIS
Unusually enlarged LV
Usual LV wall size
Thrombus at apex of LV
(confirm with contrast)
NOTE
Common end-stage 2º to
ischemic heart disease,
adaptation of myocardium to
volume overload
Heart is failing
Stasis of blood at LV apex
results in thrombus. Treat
with warfarin to prev stroke
REG
Chest
MODE
X-ray P-A
COND
Cardiomegaly, likely due to
mitral valve disease
VIS
Increased cardio/thoracic
ratio >0.55
(transverse diameter of
mediastinum / thorax)
!
Enlarged L atrium (L border
should be curved)
Thicker vascular markings
NOTE
NIGEL FONG 2011/2012
PAGE A127
M1 NOTES IN GROSS ANATOMY
5 | THORAX
D. VALVES OF HEART
Semilunar valves:
!
!
!
Atrioventricular valves
•
•
Bases of valve cusps attached to fibrous ring (maintains AV orifice patency)
Cordae tendinae from apices of papillary muscles attach to the valve cusps
•
Papillary muscles contract during ventricular systole, tightening the tendinous cords
and preventing prolapse of AV valves as ventricular pressure rises.
Semilunar valves
•
•
•
3 semilunar cusps, no tendinous cords
Edges thickened to form lunule, apex thickened further as nodule
Right coronary artery fr right aortic sinus, left coronary artery fr left aortic sinus
Systole: Pressed towards arterial walls as blood gushes out
•
• Diastole: Snap shut like an umbrella caught in the wind
Ascultation of heart valves
•
•
•
•
Aortic valve: R 2nd intercostal space, at sternal border
Pulmonary valve: L 2nd intercostal space, at sternal border
Tricuspid valve: L 4th/5th intercostal space, at sternal border
Mitral valve: L 5th intercostal space, midclavicular line (heart apex beat)
NIGEL FONG 2011/2012
PAGE A128
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Clinical: valvular heart disease
• Stenosis (narrowing): valve fails to open fully, slowing blood flow
•
•
•
•
•
Insuffficiency/incompetence: valve fails to close completely, producing
regurgitation and turbulence and compromising cardiac output
Prolapse: AV valve extends back into atrium during systole, allowing blood
regurgitation.
Turbulence produces audible murmurs
Aortic valvular insufficiency can produce a collapsing pulse
Echocardiography (e.g. doppler) allows visualization of blood flow
E. CORONARY VESSELS
!
ORIGIN
COURSE
TERM
BR
CLINICAL
Left coronary artery
!
Right coronary artery
Left aortic sinus at prox ascending aorta
Right aortic sinus at prox ascending aorta
Fwd btw left auricle & pulmonary trunk
[coronary sulcus], enters AV groove
- SS: LA
Left ant descending (ant IV) br:
- ant introventricular groove to apex
- SS: RV, LV, IV septum, AV bundle
Left circumflex br:
- coronary sulcus ard left border to pos surf
Fwd btw right auricle & pulmonary trunk,
desc vertically in right AV groove, cont
- SS: RA
Right marginal branch:
- Right border of heart, runs towards apex
- SS: RV
Posterior interventricular branch:
- Pos IV groove towards apex
- SS: LA, LV
- SS: IVS, RV, LV
Functional end arteries (insufficient collateral circulation)
Possible anastomosis: LAD & PosD in IV groove, LCx & RCA in coronary sulcus
SA nodal branch to SA node
AV nodal branch to AV node arising at
crux (pos) of heart.
Variations are very common (anastomosis can develop with slow occlusion of vessels)
Myocardial infarction results from blockage of coronary vessels (e.g. atherosclerosis)
Angina pectoris (worse on exertion) results from ischemia & less severe vessel blockage
Coronary artery bypass graft: use great saphenous vein, radial artery
Coronary angioplasty using a small inflatable balloon & stent can help to clear blockages
NIGEL FONG 2011/2012
PAGE A129
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Coronary veins
•
•
•
•
Great cardiac vein: accompanies initially the LAD artery, then the LCx artery
(unusual: blood flows in the same direction in a paired artery & vein)
Middle cardiac vein (pos IV vein): accompanies the posterior IV branch of RCA
Small cardiac vein: Accompanies the right marginal branch of RCA
Coronary sinus: Veins drain into coronary sinus, which runs from left to right in the
posterior part of the coronary sulcus and drains into the right atrium
Coronary angiography
•
•
Allows for identification of occlusion of coronary arteries
Catheter passed into ascending aorta via femoral artery
!
REG
Heart
MODE
Angiogram
COND
Normal
VIS
White: LCA
Grey: RCA
NOTE
!
Coronary artery disease
REG
Right coronary artery
MODE
CT (reconstructed below)
COND
RCA plaque >70% stenosis
VIS
Narrowing of RCA
NOTE
Plaque may be soft (lipid) or
calcified
!
NIGEL FONG 2011/2012
PAGE A130
M1 NOTES IN GROSS ANATOMY
5 | THORAX
F. NERVE SUPPLY & CONDUCTING SYSTEM
!
Conducting system
•
•
•
•
Sinuatrial (SA) node at junction of SVC & RA initiates impulses through RA walls
Atrioventricular (AV) node at posteroinferior interatrial septum near opening of
coronary sinus holds signal
Signal distribution to ventricles occurs through Purkinje fibres of the bundle of His
(AV bundle), right & left bundle branches in the IV septum, and to ventricles
Septomarginal trabecula (moderator band) in right ventricle carries part of the
right branch of the AV bundle to the anterior papillary muscles, creating a shortcut to
faciliate conduction time
!
!
Autonomic nervous supply
SYMPATHETIC
PARASYMPATHETIC
NOTES
PATHWAY
Fr sympathetic trunks of
T1-T4/T5 via
cardiopulmonary n
Presynaptic fibres fr
vagus, postsynaptic
ganlia @ atrial wall &
interatrial septum
Via cardiac plexus on
ant surf of bifurcation
of trachea, pos to
ascending aorta
NEUROTRANS
Norepinephrine
Acetylcholine
[Visceral pain: symp]
SA NODE
Inc rate of depolarization
Decrease heart rate
MUSCLE
Inc contractility
Red contracility
CORONARY
ARTERIES
Dilation
Constriction
Fight or flight inc
blood ss to heart.
Referred pain
•
•
Afferent
pain
fibres
follow
sympathetic nerves via cardiac
plexus, white rami, to T1-4
Hence cardiac pain is referred to
T1-T4 dermatomes, radiating
down the left arm, since T2 2nd
intercostal n is joined to med.
cutaneous n by intercostobrachial
n, supplying (together with T1)
axillary skin and the med side of
upper arm.
NIGEL FONG 2011/2012
PAGE A131
M1 NOTES IN GROSS ANATOMY
5 | THORAX
5. DEVELOPMENT OF THE HEART
!
A. THE PRIMODIAL
!
HEART
Early development (See section in early embryology)
•
•
•
Cardiovascular system is first major system to function
Endothelial tube forms from cardiogenic mesoderm rostral and lateral to the
buccopharyngeal membrane & neural plate
Cephalocaudal folding brings the endothelial tube downwards to its thoracic location.
Primitive heart tube
•
•
•
•
•
During lateral folding, the left and right endocardial tubes meet and fuse to form a
single primitive heart tube.
Consists of sinus venosus, common atrium, embryonic ventricle, bulbus cordis.
Cardiac myoblasts surrounding the endocardium forms the myocardium
Mesenchyme surrounding the myoblasts form the epicardium and pericardium.
Blood enters the sinus venosus and is pumped by peristalsis-like waves through
continuous muscle layers of the atrium and ventricle.
Formation of heart loop
•
•
•
As the heart tube elongates faster than the cavity, it bends to
form a C-loop and then invaginates to form an S-loop, with the
sinus venosus the most posterior.
This is also the origin of the transverse and oblique sinus.
Clinical: Dextrocardia (see radiograph) results fr the heart tube
bending L instead of R
NIGEL FONG 2011/2012
!
PAGE A132
M1 NOTES IN GROSS ANATOMY
5 | THORAX
B. DEVELOPMENT OF THE ATRIA
The following steps (atria / ventricles) occur simultaneously:
Partitioning of the atrioventricular canal
•
•
•
Endocardial cushion forms between the common atrium and embryonic ventricle
Endocardial cushions fuse, dividing the atrioventricular canal into right and left
atrioventricular canals.
Endocardial cushions serve as AV valves
Changes in the sinus venosus
•
•
•
Part of sinus venosus is incorporated into the right atrium, forming the smooth part of
the wall of the right atrium
Most of the wall of the left atrium is smooth because it is formed by incorporation of
the primordial pulmonary vein (develops from the dorsal atrial wall).
The rough part of the right atrium and both auricles are derived from the primordial
atrium.
Partitioning of the atria
•
•
•
•
•
Septum primum grows from the roof of the primordial atrium towards the fusing
endocardial cushions
Foramen primum: Septum primum leaves a large opening i.e. the foramen primum
between its free edge and the endocardial cushion.
Foramen secundum: Before the foramen primum disappears as the septum primum
fuses with the endocardial fushions, apoptosis of the central part of the septum primum
results in the formation of a foramen secundum.
Septum secundum: Grows from the roof of the atrium (cranial) adjacent to the right
side of the septum primum, forming an incomplete partition between the atria, leaving
a foramen ovale.
Valve of oval foramen: The cranial part of the septum primum gradually
disappears, such that the septum primum forms the flaplike valve of the foramen ovale.
NIGEL FONG 2011/2012
PAGE A133
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Foramen Ovale
•
•
•
•
Purpose of foramen ovale: Allows right-to-left
shunting of blood, bypassing the non-inflated
pulmonary circulation [see physiology]
Valve of foramen ovale (lower part of septum
primum) serves as a flap-like valve allowing one-way
bloodflow from the right to left atrium
Inflation of the lungs after birth decreases the
pressure of the pulmonary circulation, so the flaplike
septum primum on the left side of the foramen ovale
is pressed against and eventually adheres to the
septum secundum, closing the foramen ovale.
Clinical: Atrial septal defects e.g. patent
foramen ovale (right) that persists after birth
results in a left to right heart shunt, causing
enlargement & hypertrophy of the right atrium and
ventricle, and dilation of the pulmonary trunk.
!
!
!
C. DEVELOPMENT OF THE VENTRICLES & OUTFLOW TRACTS
!
Partitioning of the primordial ventricle
•
•
•
•
•
•
!
The muscular interventricular septum grows upwards !
from the floor of the ventricle, dividing the left and
right ventricle but leaving an IV foramen
Final closure of the IV foramen occurs by formation
of the membranous part of the IV septum, derived
from an extension of the endocardial cushion.
The primordial ventricle forms mainly left ventricle.
Further increase in ventricular volume occurs by
outward growth of cardiac myoblasts and apoptosis of
the inner part of the walls
Selective cell death also forms papillary muscles,
bridges, ridges, and cordae tendinae.
Clinical: Ventricular septal defects (Right) e.g. from
incomplete closure of the interventricular foramen
results in a massive left-to-right shunting of blood
!
Development of the bulbus cordis
•
•
•
•
Proximal 1/3: develops into the right ventricle
Middle 1/3 (conus cordis): forms conus arteriosus
(infundibulum) of the right ventricle and the aortic
vestibule of the left ventricle
Distal 1/3 (truncus arteriosus): forms the pulmonary
trunk and aorta
Aorticopulmonary septum divides R/L halves of the conus
cordis & truncus arteriosus
!
!
NIGEL FONG 2011/2012
PAGE A134
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Development of aorta & pulmonary trunk
•
•
•
Aorticopulmonary septum divides
R/L halves of the conus cordis &
truncus arteriosus
Aorticopulmonary septum undergoes
an 180º spiralling, such that the
pulmonary trunk twists around the
ascending aorta in the adult
Note: RHS and LHS aorta initially
form but RHS normally disappears
!
Clinical: Tetrology of Fallot
•
•
•
Abnormal division of the truncus arteriosus results 4 simultaneous anomalies:
1. Ventricular septal defect
2. Overriding aorta, receiving blood from the right ventricle instead of the left of from
both ventricles through a hole in the septum
3. Pulmonary artery stenosis
4. Right ventricular hypertrophy (RV pumping blood into the high-pressure aorta)
Results in shunting of blood past the lungs without it becoming oxygenated, causing
“blue baby syndrome” (cyanosis)
With surgical treatment, compatible with normal adulthood.
Ductus arteriosus
•
•
•
•
•
The ductus arteriosus allows blood flow from the pulmonary trunk to the aorta,
bypassing the pulmonary circulation
Upon lung inflation at birth, pulmonary resistance decreases and blood flows into the
pulmonary trunk for oxygenation. Oxygenation of the blood in the aorta triggers
closure of the ductus arteriosus via smooth muscle contraction.
The ductus arteriosus eventually is replaced by fibrous tissue, becoming the
ligamentum arteriosus.
Clinical: Patent ductus arteriosus occurs when the ductus arteriosus fails to
involute after birth. This is more common among infants with respiratory distress
syndrome, since tissue hypoxia may affect the triggering of smooth muscle contraction.
Clinical: Coarctation of the aorta – see radiograph
NIGEL FONG 2011/2012
PAGE A135
M1 NOTES IN GROSS ANATOMY
5 | THORAX
6. MEDIASTINUM
A. AORTA
!!
Route & Branches
ASCENDING
AORTA
ARCH OF
AORTA
DESCENDING
(THORACIC)
AORTA
CLINICAL
BRANCH
SS
Left ventricle, aortic orifice
Ascending aorta is intrapericardial
Coronary arteries (R/L)
Heart
Begins pos to 2nd right sternocostal jt,
Arches sup, pos, to the left, then inf.
Ant to right pulmonary artery &
trachea, pass over root of left lung
Descends pos to root of L lung besides
T4 (opp sternal angle)
Brachiocephalic trunk
(at right SC joint, div
into R subclavian & R
common carotid)
R UL
R H&N
Left common carotid
L H&N
Left subclavian
L UL
Begins at left side of T4
Incline ant & med to reach ant surf of
vertebra (displacing esophagus to RHS)
At T12, pass through aortic opening of
diaphragm, becomes abdominal aorta
Posterolat: Pos intercostal
Subcostal arts
Thorx wall
Abd wall
Lateral: Bronchial arts
Lungs
Ant midline: Esophageal
Esophagus
Much variation in the branches coming out of the arch of the aorta
Ligamentum arteriosus (remnant of fetal ductus arteriosum) connects the
bifurcation of the pulmonary trunk to the lower concave surface of the aortic arch
(see embryology).
!
Relations of the arch of the aorta
[Left]
[Sup]
[Ant]
[Inf]
[Pos]
L lung
Branches of arch of aorta, crossed ant by left brachiocephalic vein
Left phrenic nerve & Left vagal trunk
Bifurcation of pulmonary trunk & left main bronchus
Ligamentum arteriosum
Left recurrent laryngeal nerve (fr L vagus), hooking around arch of aorta
Left recurrent laryngeal nerve, passing upwards towards the larynx
Trachea & Deep cardiac plexus on ant surf of bifurcation of trachea
Esophagus
Thoracic duct, tracheobronchial lymph nodes
Thoracic vertebral column
NIGEL FONG 2011/2012
PAGE A136
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Congenital defects
•
•
•
Patent ductus arteriosus (see embryology)
Transposition of great vessels / arteries (e.g. due to incorrect spiral division of the
truncus arteriosus)
Coarctation of the aorta
!
REG
MRI/Xray
MODE
Sagittal
COND
Coarctation of the aorta
VIS
Coarctation near ligamentum
arteriosum
R: Stent placed
NOTE
Congenital defect: aortic wall
contraction when ductus
arteriosus closes.
See below
!
REG
X-ray
MODE
PA
COND
Coarctation of the aorta
VIS
Notching of the ribs due to
increased blood flow in
intercostal artery running in
costal groove.
Due to dvt of collateral
circulation from arch of aorta
– subclavian art – internal
mammary art – intercostal
arteries – thoracic aorta
NOTE
!
!
Catheterization of the heart
•
•
•
!
Clinical obs: radial-femoral
delay, diminished femoral
pulses
Femoral approach: catheter introduced from femoral artery, passing through the
external iliac artery, common iliac artery, abdominal aorta, thoracic aorta, arch of
aorta, ascending aorta, aortic sinuses and aortic valve, and then into the LV
Radial approach: catheter introduced from radial artery, through the brachial artery
via the cubital fossa, subclavian artery, [brachiocephalic trunk if RHS], arch of aorta,
ascending aorta, aortic sinuses and aortic valve, and then into the LV
Right heart caterization: Go through the vein instead of the arteries. Same direction of
bloodflow, so the valves are not an issue.
NIGEL FONG 2011/2012
!
PAGE A137
M1 NOTES IN GROSS ANATOMY
5 | THORAX
B. VEINS
!
ORIGIN
COURSE
Sup vena cava
Inf vena cava
Brachiocephalic v form pos to sternoclavicular jts by
union of int jugular & subclavian veins.
Unite to form SVC at 1st right costal cartilage
Arises in abdomen by union
of common iliac veins.
Passes inferiorly in RHS of sup mediastinum
anterolat to trachea, posterolat to asc aorta
Opp T8: Pierce central
tendon of diaphragm
TERM
BR
SS
CLINICAL
!
3rd costal cartilage
Enters right atrium
Around T7
Azygos vein (around T5)
Blood from all structures sup to diaphragm (head, neck,
UL) but excl. lungs/heart
Drain structures inf. to
diaphragm
Azygous venous system connects sup & inf vena cava, providing collateral circulation
!
!
ORIGIN
COURSE
TERM
BR
SS
CLINICAL
Azygos vein
Hemiazygos vein
Ascend in pos mediastinum, close to RHS
of bodies of T5-12 vertebrae
LHS of vertebral column pos to aorta
Arches sup over root of R lung (like aorta
over root of the L lung) to drain into SVC
T8/T9: hemiazygos (fr bottom) & accessory
hemiazogos (fr top) drain into azygos.
Pos inf vena cava, renal veins, and ascending lumbar veins.
Pos intercostal veins, subcostal vein, lumbar veins, renal veins (highly variable)
Drain blood from back, pos thoracoabdominal walls, and mediastinal viscera
(pericardium, diaphragm, bronchi, esophagus).
Connects sup & inf vena cava, providing collateral circulation. Highly variable
NIGEL FONG 2011/2012
PAGE A138
M1 NOTES IN GROSS ANATOMY
5 | THORAX
C. LYMPHATIC DRAINAGE
Lymphatic drainage of the thorax
•
•
•
•
Superficial ant thoracic wall drains into ant axillary nodes
Superficial pos thoracic wall drains into pos axillary nodes
Deep ant intercostal areas drain into parasternal (internal thoracic) nodes on either
side of the sternum, which in turn drain into the broncho-mediastinal trunk.
Deep pos intercostal areas drain into (posterior) intercostal lymph nodes lat to the
vertebral column, which later drain into the thoracic duct.
!
ORIGIN
Thoracic duct
From cisterna chyli in abdomen
Right lymphatic duct
Very short duct receiving
right jugular, subclavian,
bronchomediastinal trunks
COURSE
Aortic opening in diaphragm, on RHS of aorta. L border
of esophagus at sternal angle (T4), follows esophagus up
to root of neck.
TERM
Loop ard carotid sheath, in front of vertebral vessels.
Cross subclavian artery to enter L brachiocephalic vein
at L venous angle (junc of subclavian & int jugular vein)
Opens into beginning of R
brachiocephalic vein (R venous
angle)
Root of neck: recv left jugular, subclavian,
bronchomediastinal lymphatic trunks
-
DRAINS
Whole body except that drained by R lymphatic duct
R H&N, R UL, R upp thorax.
CLINICAL
Thoracic duct can be lacerated in accident or surgery
(colourless and hard to identify); result in chylothorax
Trunks may open directly into
great veins.
BR
!
NIGEL FONG 2011/2012
PAGE A139
M1 NOTES IN GROSS ANATOMY
5 | THORAX
D. NERVES
!
ORIGIN
COURSE
TERM
BR
SS
CLINICAL
!
Vagus nerve (R/L)
Phrenic nerve (R/L)
Fr brainstem.
R: posterolat to brachiocephalic trunk
L: between L common carotid & subclavian
C3-C5 anterior rami
R: Along right side of R brachiocephalic v
L: Along left side of L subclavian
Pos to root of lungs
Forms pulmonary plexus, leaves as 1 nerve
Contributes to cardiac plexus
Ant to root of lungs
Along sides of pericardium
Forms esophageal plexus and passes
through esophageal opening of diaphragm
to reach pos stomach
Pierces diaphragm
Recurrent laryngeal nerves:
R: hook ard R subclavian art
L: hooks ard arch of aorta lat to
ligamentum arteriosum
Visceral parasympathetic
(to lungs, heart, and GI tract)
Diaphragm (motor & sensory)
Sensory: diaphramatic/mediastinal pleura,
pericardium, peritoneum cov ctrl diaphrag
Injury to recurrent laryngeal nerves (e.g. in
aneuysm of arch of aorta) affect the voice
Paralysis of one side of the diaphragm
results from damage to the phrenic nerve
Sympathetic nerves
•
•
Sympathetic trunk is visible in the posterior mediastinum lateral to the vertebral
column once the lungs are removed.
Lower thoracic splanchnic nerves (greater, lesser, least) supplying the abdominal
viscera may also be visible crossing anterior to the vertebral column (see abdomen)
!
!
NIGEL FONG 2011/2012
PAGE A140
M1 NOTES IN GROSS ANATOMY
5 | THORAX
!
!
E. OTHER STRUCTURES
!
Thymus
LOC
Inf neck & ant sup. mediastinum, extending into ant mediastinum
STR
Flat gland with flask-shaped lobes. Involutes and is mostly replaced by fat after
puberty (but continues to remain functional)
FUNC
BLOOD SS
!
Trachea
Inf thyroid & int thoracic arteries
Lymph: parasternal, brachiocephalic, tracheobronchial nodes.
LOC
Begins in neck as cont of larynx below C6
[Ant]: sternum, thymus, great vessels
[Pos]: Esophagus, left recurrent laryngeal n
[RHS]: Azygos vein, right vagus nerve, pleura
[LHS]: Arch of aorta, left vagus/phrenic n, pleura
STR
C-shaped cartilage and trachealis muscle
connecting the pos end (see Histology)
FUNC
!
!
Immune development (T-cell maturation)
Airway (see tracheobronchial tree)
BLOOD SS
Inf thyroid arteries, bronchial arteries
Lymph: pretracheal, paratreacheal, deep cervical
NERVE SS
Vagus, recurrent laryngeal n
Trachealis muscle: sympathetic n
CLINICAL
See lungs & pleurae
NIGEL FONG 2011/2012
PAGE A141
M1 NOTES IN GROSS ANATOMY
5 | THORAX
Esophagus
LOC
C6: Continues from laryngopharynx
Neck: ant to vert column, pos to trachea. Passes
inf & left but pushed to midline by aortic arch.
[Ant] Trachea, L recurrent laryngeal n, L
bronchus, pericardium, L atrium
[Pos] Thoracic vertebrae, thoracic duct, azygos v
[RHS] Mediastinal pleura, azygos vein
[LHS] L subclavian art, aortic arch, thoracic duct,
mediastinal pleura
T10: Passes thru diaphragm (esophageal hiatus)
T11: Enters cardial orifice of stomach
STR
Muscular tube with 3 constrictions:
(1) At junction of pharynx and esophagus
(2) Where the aortic arch & left bronchus
cross anteriorly
(3) At the passage through the diaphragm
FUNC
BLOOD SS
Passage of food into the stomach.
Sup 1/3
Mid 1/3
Inf 1/3
Inf thyroid art
Descending aorta
Left gastric art.
Inf thyroid veins
Azygos veins
left gastric vein (to portal vein)
Lymph: deep cervical, mediastinal, celiac nodes & nodes at L gastric blood vessels
!
!
NERVE SS
Sympathetic fibres from sympathetic trunks
Surr by the esophageal plexus (from parasym vagus nerves) in the lower thorax
CLINICAL
Strictures develop at constrictions after drinking caustic fluids (due to delay in passage)
Stuck fish bones may damage the left atrium due to the close relationship
F. RELATIONS & CROSS SECTIONAL ANATOMY
!
Superior mediastinum
From anterior to posterior:
1. Thymus
2. Veins (brachiocephalic veins and
superior vena cava)
3. Arteries (arch of aorta and roots of
major branches)
4. Trachea
5. Esophagus
6. Thoracic duct & lymphatic trunks
!
NIGEL FONG 2011/2012
PAGE A142
M1 NOTES IN GROSS ANATOMY
!
5 | THORAX
Relations at the sternal angle (T4)
Key to relations table :
Sup mediastinum
R lung
Middle mediastinum
L lung
Pos mediastinum
!
!
[Ant]
Skin & fascia of ant thoracic wall
Sternum (sternal angle / manubrium)
Internal thoracic artery & vein
Thymus gland
[R]
Right phrenic nerve
Right main bronchi
Right vagus nerve
Sympathetic trunk
Scapula & muscles
Sup vena cava, brachiocephalic v…..
.……..Arch of aorta
Pretracheal lymph nodes
Trachea
Arch of azygos vein
Oesophagus
Thoracic duct & lymphatic trunks
T4 Vertebrae / Intervertebral disc
Spinal cord
Rhomboid & Trapezius
[L]
Left phrenic nerve
Left main bronchi
Left vagus nerve
Sympathetic trunk
Scapula & muscles
[Pos]
!
!
!
NIGEL FONG 2011/2012
PAGE A143
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
CHAPTER 6: NORMAL STRUCTURE AND DEVELOPMENT OF THE
6 | ABDOMEN
!
!
1. ANTERIOR ABDOMINAL WALL
!
A. PLANES & REGIONS
!
Location of the abdominal cavity
•
•
•
Between diaphragm and pelvic girdle
Continuous with the pelvic cavity (pelvic inlet is the boundary)
May extend into 4th intercostal space; hence spleen & liver protected by thoracic cage.
4 Quadrants
•
•
Transverse transumbilical plane and median plane divides abdomen into 4 quadrants
However the umbilicus is a poor landmark; shift downwards in pregnancy or obesity.
Alternative names:
Pubic = Hypogastric
Flank = lumbar
Groin = inguinal
!
!
9 Regions
•
•
•
•
Division into 9 regions based on 2 sagittal & 2 transverse planes
Sagittal plane
- Midclavicular plane / midinguinal plane [crosses costal margin at rib 9]
- Or use lateral rectus plane (linea semilunaris): lat line of rectus muscle
Transverse plane 1
- Transpyloric plane (L1), passes through pylorus of stomach (rib 9)
- Subcostal plane (L3), passing through inf border of 10th costal cartilage
Transverse plane 2
- Transtubercular plane (L5) through easily palpable iliac tubercles
- Interspinous plane through ASIS
NIGEL FONG 2011/2012
PAGE A144
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
B. FASCIA & MUSCLES
!
Muscles
•
•
•
•
•
3-ply flat muscle layer of the abdomen is similar to that of the thorax. Superficial to
deep: external oblique, internal oblique, transversus abdominis.
Like the thorax, neurovascular plane is located between 2nd and 3rd layer.
2 vertical muscles: rectus abdominis and pyramidalis (insignificant)
Muscles compress the abdominal viscera to maintain or increase intra-abdominal
pressure e.g. in childbirth or forced expiration (in opposition to diaphragm).
Int oblique & rectus also responsible for flexing the trunk and maintaing posture
(preventing lordosis – excessive side-side swaying)
!
MUSCLE
FIBRE DIR
ORIGIN
INSERTION
1 Ext oblique
Fwd/down
Lower 8 ribs
Linea alba, iliac crest
Compress abd
2 Int oblique
Bwd/down
Ant 2/3 iliac crest, lat
2/3 inguinal lig
Thoracolumb fascia
Linea alba,
lower 3 ribs, pubic
crest, pectineal line
Compress abd
Flex trunk
Transverse
Costal cartilage, rib 7-12
Iliac crest, lat 1/3
inguinal lig
Linea alba,
pubic crest,
pectineal line
Compress abd
Xiphoid process,
costal cartilage 5-7
Flex trunk
Compress abd
Linea alba
Insignificant
Transversus
3
abdominis
Rectus
abdominis
Sup-inf
- Pyramidalis
Sup-inf
-
Pubic crest, tubercle,
symphysis
ACTION
!
!
!
NIGEL FONG 2011/2012
PAGE A145
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Rectus sheath
•
•
•
•
Rectus abdominis (and pyramidalis) enclosed within the rectus sheath
- Ant wall: aponeurosis of external oblique & half of int oblique
- Pos wall: aponeurosis of half of int oblique & transversus abdominis
Aponeuroses interweave with opposite side, forming a linea alba (midline raphe)
Arcuate line: below this (midway btw umbilicus & pubic symphysis), all aponeuroses
move ant to rectus muscle, rectus is in direct contact with transversalis fascia
Clinical: hernias may result due to defects in the wall. EG umbilical hernias, epigastric
hernias (through linea alba), spigelian hernias (through semilunar lines)
Fascia
•
•
Superfacial fascia below the umbilicus splits into 2 a superficial fatty layer (Camper’s
fascia) and a deeper membranous layer (Scarpa’s fascia) which is cont w Colles’ fascia
Transversalis fascia lines deep surf of transversalis muscle, sup to parietal peritoneum
NIGEL FONG 2011/2012
PAGE A146
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
C. NEUROVASCULAR STRUCTURES
Nerve supply
ORIGIN
COURSE
TERM
BRANCH
SS
Motor
Sensory
CLINICAL
!
Anterior ramus of T7 – T11 (thoracoabdominal nerves), T12 (subcostal nerve), L1
Thoracoabdominal nerves continue from intercostal spaces
Run between internal oblique & transversus abdominis muscles
Ant abdominal cutaneous branches: piece rectus sheath near median plane.
L1: divides into iliohypogastric and ilioinguinal nerve (ant scrotum / labia majora,
and small cutaneous branch to thigh)
Lat cutaneous branch (ant/pos div): supply s/c tissue at ant axillary line
Ant abdominal wall muscles
Dermatomal distribution: T7-9 sup to umbilicus, T10 umbilicus, T11-L1 inf to umbilicus
See referred pain from appendicitis
!
!
!
Blood supply
•
•
•
•
Superior & inferior epigastric arteries (below)
10th & 11th intercostal arteries, subcostal artery
Deep circumflex iliac art (from ext iliac art), sup circumflex iliac artery (fr femoral art)
Deep veins follows arteries, ther are also variable superficial veins
ORIGIN
Sup epigastric artery
Inf epigastric artery
Cont of int thoracic artery
From external iliac artery
COURSE
Runs in rectus sheath deep to rectus
TERM
CLINICAL
Sup & inf epigastric arteries anastamose in the umbilical region
Sup & inf epigastric arteries provide collateral circulation in the event of blockage of the
descending aorta.
!
NIGEL FONG 2011/2012
PAGE A147
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Lymphatic drainage
•
•
Superficial lymphatic vessels accompany subcutaneous veins
- Sup to transumbilical plane: drain to axillary lymph nodes
- Inf to transumbilical plane: drain to superficial inguinal nodes
Deep lymphatic vessels accompany deep veins, draining to external iliac, common iliac,
or parasternal nodes.
Surgical incisions: considerations
•
•
•
Incision chosen to allow adequate exposure, avoid bony boundaries, avoid (esp motor)
nerves, maintain blood supply, minimize injury to muscles and allow favourable healing
Muscles are split in the direction of their fibres, instead of transected (except rectus
abdominis)
Muscles and viscera retracted towards and not away from their neurovascular supply.
Surgical incisions: options
•
•
•
•
•
Midline incision avoids cutting muscle,
vessels, and nerves. However healing is
more difficult due to poor blood supply
Paramedian incision: rectus must be
retracted laterally.
McBurney point: appendectomy
Suprapubic (bikini) incisions: O&G
Transverse incisions: rectus abdominis can
be transected as a new transverse band
forms when segments are rejoined. However
transaction at the tendinous intersections
endangers cutaneous nerves and sup
epigastric vessels
!
!
NIGEL FONG 2011/2012
!
PAGE A148
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
D. TESTES & SCROTUM
Embryology: Descent of the testes
•
•
•
•
•
•
Testes develop in superior lumbar region in the posterior abdominal wall and descend
into scrotum through what becomes the inguinal canal
- Carries spermatic cord & blood supply from abdomen with it
- Extra-abdominal portion of the gubernaculum (fr caudal pole of testes to inguinal
reg) outgrows, pulling testis along [hormonal influence: androgen & MIS]
Processus vaginalis, a peritoneal diverticulum, outpouches to enter the primordial
scrotum, carrying muscular and fascial layers before it
- During descent, forms inguinal canal together w musculofascial layers of abd wall
- Processus vaginalis obliterates at birth or shortly after
Hence the testes is ensheathed by musculofascial outpouching of the anterolateral
abdominal wall i.e. the scrotum
In females, the ovaries develop in a similar region but do not descend all the way
through the inguinal canal, only the round ligament does.
Clinical: Cryptorchism: Undescended testes cannot prod sperm hv malignancy risk.
Clinical Hydrocele: Unobliterated processus vaginalis lets periton. fluid enter scrotum
NIGEL FONG 2011/2012
PAGE A149
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Layers of the scrotum
•
•
Skin, with midline ridge indicating line of fusion of L/R labioscrotal swellings
Layers covering the testes
- corresponding to layers of ant abd wall:
1. Skin of scrotum
2. Dartos fascia & muscle
- fr subcutaneous fascia
3. Ext spermatic fascia
4. Cremasteric fascia & muscle
•
•
•
- from ext oblique aponeurosis
- from int oblique muscle
5. Int spermatic fascia
- from fascia transversalis
6. Parietal layer of tunica vaginalis
7. Tunica albuginea (see testes)
No covering from transversus abdominis acquired as processus vaginalis passes under
transversus muscle.
Tunica vaginalis (visceral & parietal layers): obliteration of the upper part of the
processus vaginalis results in formation of a closed sac, within which testes move freely
Scrotum is both inguinal and perineal in vascular and nerve supply, lymphatics drain
to the sup inguinal nodes.
Temperature regulation by the scrotum
•
•
Spermatogenesis requires a constant temperature cooler than core temperature
Cremaster & dartos muscles regulate temperature:
- Cold: contract to draws the testes superiorly into the scrotum
- Warm: relax to allow the testes to descend deeply into the scrotum
- Cremaster muscle is skeletal, innervated by genital branch of genitofemoral n (L1-2)
- Dartos muscle is smooth
NIGEL FONG 2011/2012
PAGE A150
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
E. INGUINAL REGION
Inguinal canal
LOC
WALL Ant
Pos
Roof
Floor
CONTENTS
4cm oblique inferomedial passage through inferior anterolateral abdominal wall
Parallel and superior to med half of inguinal ligament.
Ext oblique aponeurosis, reinforced laterally by int oblique originating fr inguinal lig
Transversalis fascia, reinforced medially by conjoint tendon (inguinal flax): merger
of int oblique & transversus abdominis aponeuroses
Arching fibres of int oblique & transversus abdominis
Medial half of inguinal ligament
M: Spermatic cord (vas deferens, testicular artery, pampiniform vein plexus)
F: Round ligament of the uterus
Genital branch of genitofemoral nerve
Ilio-inguinal nerve passes through part of the canal, exiting through superficial ring
ENTRANCE
EXIT
CLINICAL
NIGEL FONG 2011/2012
Deep inguinal ring: Midpoint btw ASIS & pubic symphysis, lat to inf epigastric
vessels (beginning of evagination of transversalis fascia)
Superficial inguinal ring: ∆ opening in aponeurosis of ext oblique superior to
pubic tubercle – [base]
pubic crest,
[med crus] to pubic crest/symphysis,
[lat crus] to pubic tubercle.
Intercrural fibres prevent further widening of the ring.
• Cremasteric reflex: contraction of cremaster is elicited by lightly stroking skin
on medial aspect of sup thigh (SS by ilioinguinal n).
• Vastectomy: the vas deferens may be ligated near the superficial inguinal ring as
a means of birth control. Care has to be taken not to ligate the testicular artery
PAGE A151
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Inguinal hernias
•
•
•
Protrusion of parietal peritoneum and viscera from abdominal cavity.
Bowel and fat may become stuck, causing pain or ischema [the more narrow indirect
hernia is more dangerous]
Clinical examination: hernia bulges on coughing. When pt lies supine, herniated mass
drops back into abdominal cavity. Ask pt to stand while pressing superficial ring
(blocking herniation), and gradually move finger laterally. Immediate appearance of a
lump suggests direct hernia, herniation only after unblocking deep ring suggests
indirect hernia.
COURSE
LANDMARK
DIRECT (ACQUIRED) HERNIA
INDIRECT (CONGENITAL) HERNIA
Leaves directly through superficial
inguinal ring.
Rarely enters scrotum
Deep inguinal ring, inguinal canal (within
processus vaginalis), superficial ring.
Commonly enters scrotum
Med to inf epigastric vessels & pubic
tubercle
Lat to inf epigastric vessels & pubic
tubercle
Note: inguinal hernia appears above pubic tubercle, femoral hernia appears below.
CONTENTS
CAUSE
EPIDEMEO
Peritoneum + transversalis fascia (lies
outside inner 1-2 coverings of cord)
Peritoneum + all 3 fascial coverings of
spermatic cord / round ligament
Weak ant abd muscle wall in inguinal
(Hesselbach) triangle (btw inf epigastric
art, rectus, and inguinal ligament).
Patent processus vaginalis,
Esp in older men, e.g. due to raised
intra-abdominal pressure w repeated
coughing, surgical nerve damage
More common, esp in young males.
(women have a smaller inguinal canal)
Note: inguinal hernia occurs above public tubercle, femoral occurs below.
NIGEL FONG 2011/2012
PAGE A152
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
2. DEVELOPMENT OF THE GUT
!
A. OVERVIEW OF DEVELOPMENT
!
Germ layer derivatives
•
•
•
•
Gut develops in the embryonic period (week 4-8)
Endoderm gives rise to epithelium of gut and parenchyma of organs that develop fr gut
Mesoderm gives rise to connective tissue of gut, stroma of organs, and peritoneum
Epithelial-mesenchymal interactions result in differentiation of the gut into the
pharyngeal gut (sometimes considered part of foregut), foregut, midgut, and hindgut
FOREGUT
MIDGUT
HINDGUT
Oral cavity to duodenum
(prox half of 2nd part)
Duodenum (distal half of
2nd part) to transverse
colon (prox 2/3)
Transverse colon (distal
1/3) to anal canal (upper
1/2)
Liver, pancreas, gall
bladder, bilary system
Appendix
BLOOD SS
Celiac trunk
Sup mesentric vessels
Inf mesentric vessels
NERVE SS
Vagus nerve
(parasympathetic)
Vagus nerve
(parasympathetic)
Pelvic splanchnic
(parasympathetic)
DIGESTIVE
ACC ORGANS
NOTES
Spleen dvp fr mesoderm,
not as outgrowth of gut
Distal 1/2 anal canal not
a derivative of gut
!!
!
Development of peritoneal cavity
•
•
•
•
Abdominal organs grow into the peritoneum like lungs into the pleurae
Early gut tube is oriented longitudinally and suspended from surrounding walls by a
large dorsal mesentry and a smaller ventral mesentry (both anchored to diaphragm).
Hence early gut tube is intraperitoneal.
Retroperitoneal (extraperitoneal): kidneys, adrenals, ascending & descending colon,
duodenum, and pancreas are covered with peritoneum only anteriorly and contact the
posterior abdominal wall posteriorly (bladder has peritoneum only superiorly)
Intraperitoneal: all other organs remain almost completely covered with visceral
peritoneum (like invagination into the closed peritoneal sac – see lungs & pleurae).
They remain suspended to the posterior abdominal wall by a mesentry (carrying
neurovascular bundles)
NIGEL FONG 2011/2012
PAGE A153
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
B. DEVELOPMENT OF SPECIFIC ORGANS
!
!
NIGEL FONG 2011/2012
!
!
PAGE A154
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Rotation of stomach
•
•
•
•
•
•
Developing stomach rotates clockwise 90º (viewed cranially). Ventral border (lesser
curvature) moves to right and dorsal border (greater curvature) moves to left
Hence left vagus supplies ant wall while right vagus supplies pos wall.
Dorsal mesentry (containing spleen and pancreas) is originally in midline but is carried
to the left during rotation.
The space enclosed by the balloned dorsal mesentry of the stomach becomes the lesser
sac, which remains connected to the greater sac through a restricted opening – the
omental (epiploic) foramen
Part of the dorsal mesentry initially forming the inferior part of the lesser sac greatly
enlarges to form the greater omentum
The ventral mesentry connects the stomach to the liver and eventually becomes the
lesser omentum
Biliary system
•
•
•
•
Liver, gallbaldder and billary ducts arise from the hepatic diverticulum, a ventral
outgrowth of the foregut that grows into the septum transversum (which forms ventral
mesentry in the region).
Endoderm gives rise to hepatocytes and epithelial lining of hepatic sinusoids.
Mesoderm gives rise to stroma of liver including Kupffer cells, hemopoietic cells, and
connective tissue.
Ventral mesentry gives the falciform ligament from the liver to ventral abdominal wall
Pancreas
•
•
•
•
•
•
•
•
Ventral bud develops from the hepatic diverticulum, dorsal bud develops from
outgrowth of foregut, the buds later rotate around the duodenum and fuse
Failure of fusion of pancreatic duct (9% of pop) results in an accessory pancreatic duct.
Annular pancreas: Improper merger w ventral bud encirculing & obstructing duodenum
Art ss is fr both sup mesentric art & celiac trunk due to close assoc w duodenum.
Endoderm gives rise to parenchyma of pancreas (forms network of tubules and acini)
Mesoderm gives rise to pancreatic islets.
Dorsal mesentry of stomach, containing pancreas and spleen, swings left and partly
fuses with left side of pos abdominal wall. Hence pancreas becomes 2º retroperitoneal
Note: spleen develops from mesoderm in the dorsal mesentry between body wall and
presumptive stomach, it is not endodermal in origin.
NIGEL FONG 2011/2012
PAGE A155
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Duodenum
•
•
•
•
Junction of foregut and midgut part of the duodenum is just distal to the origin of the
bile duct.
Duodenum is initially a C-shaped loop that projects ventrally, however with rotation of
the stomach, the duodenum rotates to the right and is pressed against the posterior
abdominal wall, fusing to become secondarily retroperitoneal.
Ventral mesentry of duodenum disappears
Clinical: Lumen of the duodenum is temporarily obliterated because of epithelial cell
proliferation, recanalization occurs via degeneration of epithelial cells, however
occlusion of the lumen results in duodenal atresia / stenosis (incomplete occlusion).
Intestines & Colon
•
•
•
•
•
•
The primary intestinal loop has a connection with the yolk sac through the vitelline
duct (omphaloenteric duct / yolk stalk).
Meckel’s diverticulum: A persistant remnant of the vitelline duct (60cm fr ileocecal
junc), possessing a small area of gastric mucosa. May bleedand cause pain.
In 6th week, rapid growth of GIT results in a loop of the midgut herniating out the
abdominal cavity and into the umbilical cord, but as the connection with the yolk sac
is lost, the midgut returns to the abdominal cavity.
Clinical: Congenital umbilical hernia occurs if the gut loop fails to return to the
abdominal cavity
In week 6-10, midgut loop rotates counterclockwise 270º (cranial/front view) with
superior mesentric artery at the center of the axis of rotation. (90º of rotation occurs
during herniation and the other 180º after return of loop to the abdominal cavity)
Hence ascending colon swings to the right, descending colon swings to the left.
Ascending and descending colon fuse with posterior abdominal wall, becoming
secondarily retroperitoneal.
!
NIGEL FONG 2011/2012
PAGE A156
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Anal canal
•
•
•
•
•
Hindgut initially opens into cloaca. A urorectal septum divides the cloaca into ant
region (bladder) and pos region (anal canal) [see kidney development]
Prox 2/3 of anal canal develops from hindgut, distal 1/3 of anal canal develops from
ectoderm, and the pectinate line marks the junction between the two.
This explains the transition from columnar epithelium (endodermal) above the
pectinate line, to stratified squamous epithelium (ectodermal) below.
Hindgut-derived anal canal is supplied by the inf mesentric artery and autonomic
pelvic splanchnic nerves, while ectoderm-derived anal canal is supplied by inf rectal
artery and somatic inf rectal nerves.
Clinical: tumours in the superior part are painless and arise from columnar epithelium,
those in the inferior part are painful and arise from stratified squamous epithelium
Oropharyngeal & cloacal membrane
•
•
•
•
Oropharyngeal (buccopharyngeal) membrane btw primitive mouth and pharynx is the
cranial end of the gut
Caudal end of gut is marked by the cloacal membrane, at pectinate line of anal canal.
At these membranes, endoderm meets ectoderm. The absence of epithelialmesenchymal interactions result in the breakdown of both membranes
In examination of the newborn, if the cloacal membrane fails to break down (e.g. due
to mesodermal cells migrating between the endodermal and epidermal layers) it may be
found on PR
NIGEL FONG 2011/2012
PAGE A157
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
3. ABDOMINAL VISCERA
A. PERITONEUM
Layers & innervation
•
Parietal peritoneum lines the abdominal wall (ant, deep to transversalis fascia)
•
•
Parietal peritoneum receives somatic innervation and is sensitive to well-localized pain
Visceral peritoneum covers the viscera
•
Visceral peritoneum receives autonomic innervation, irritation results in referred and
poorly localized sensations of discomfort or reflex visceral motor activity
Peritoneal cavity
•
•
•
•
The peritoneal cavity is a potential space between the parietal and visceral peritoneum
The greater sac is the larger part of the peritoneal cavity. A surgical incision through
the anterolateral abdominal wall enters the greater sac.
The lesser sac (omental bursa) lies posterior to the stomach. It includes the space
behind the lesser omentum (superior recess, all the way to the diaphragm) and between
the layers of the greater omentum (inferior recess).
Omental bursa permits free movement of the stomach
Epiploic (omental) foramen
•
•
Epiploic (omental) foramen allows communication
(and infection spread) btw omental bursa & greater sac
Loc pos to free edge of lesser omentum (hepatoduodenal
ligament) which also contains portal triad.
- Ant: Hepatoduodenal ligament containing hepatic
portal vein (pos), bile duct (ant left), hepatic artery
(ant right)
- Pos: IVC, right crus of diaphragm
!
- Sup: Liver
- Inf: first part of duodenum
•
Clinical: clamping portal triad allows stoppage of bleeding.
!
NIGEL FONG 2011/2012
!
PAGE A158
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Basis of omenta & ligaments
•
•
•
Omenta: double-layered peritoneal folds.
Ligaments: double layer of peritoneum connecting an organ w organ or abdominal wall.
The omenta, ligaments, and mesentries are consequences of embryological development
where the liver, stomach, spleen, pancreas and left kidney lie in the same anteroposterior axis of vental and dorsal mesentry.
Greater omentum
•
•
•
•
•
•
Greater omentum is the first structure seen when the peritoneal cavity is opened. In
surgery, the lesser sac can be accessed through the greater omentum
It attaches from the greater curvature of stomach and first part of duodenum, drapes
inferiorly (apron-like) over the transverse colon and small intestine, turns posteriorly
and adheres to the peritoneum on the transverse colon
On a continuous line of attachment superior to apron-like part, the greater omentum
also connects the stomach to the spleen by the gastrosplenic ligament and to the
inferior surface of the diaphragm by the gastrophrenic ligament.
In addition, splenorenal ligament connects the left kidney to the spleen, completing the
derivatives of the dorsal mesentry of the stomach.
Greater omentum contains fat.
Greater omentum can seals off an inflammed area of the GI tract. Bowel inflammation
results in cecessation of peristalsis (local paralytic ileus), while movements of the
remaining bowels massages the greater omentum to the paralytic region. The greater
omentum then adheres to the diseased area.
Lesser omentum
•
•
•
Lesser omentum extends from the lesser curvature of the stomach and first part of
duodenum to the inferior surface of the liver
Lesser omentum can be subdivided into a medial hepatogastric ligament and lateral
hepatoduodenal ligament.
Hepatoduodenal ligament ends laterally as a free margin (ant border of epiploic
foramen) which contains the portal triad (hepatic artery, bile duct, portal vein)
NIGEL FONG 2011/2012
PAGE A159
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Ligaments of the liver
•
•
•
•
•
•
Falciform ligament (derivative of ventral mesentry) connects the liver to the
anterior abdominal wall (note: ventral mesentry of the rest of the gut degenerates)
Hence the ventral mesentry – dorsal mesentry axis is: ant wall, falciform ligament,
liver, lesser omentum, stomach, gastrosplenic ligament, splenorenal ligament, pos wall.
The falciform ligament is continuous inferiorly with the round ligament of liver
(ligamentum teres hepatitis), the remnant of the umbilical vein
Together with the ligamentum venosum, the remnant of the ductus venosus, the
falciform ligament, round ligament, and ligamentum venosum appear to form a
continuous ring.
Hence the double-layer visceral peritoneum from the lesser omentum (ligamentum
venosum post & round ligament ant) splits to surround the liver (except at its bare
area), then unite again to form the falciform ligament and join the ant abdominal wall.
At the bare area, the liver contacts the diaphragm (embryological basis: hepatic
diverticulum grows into the septum transversum). Surrounding the bare area are:
- Ant (sup) / pos (inf) coronary ligaments (cresent shape)
-
R/L triangular ligament
Spaces around the liver
•
•
•
Subphrenic recess between the liver and the diaphragm is divided into noncommunicating R/L halves by the falciform ligament.
Hepatorenal recess (Morrison pouch) lies btw the right visceral surface of liver
and right kidney / suprarenal gland
Clinical: The hepatorenal recess is a gravity-dependent part of the peritoneal cavity in
the supine position, it is normally a potential space but fluid may accumulate (even the
lesser omentum drains into the hepatorenal recess).
!
!
!
!
NIGEL FONG 2011/2012
!
PAGE A160
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Mesentries
•
•
•
•
Mesentries attach viscera to the posterior abdominal
wall, allowing movement of viscera and passage of
neurovascular bundles.
The mesentry connects the jejunum and ileum to
the posterior abdominal wall.
Transverse mesocolon connects transverse colon
to posterior abdominal wall
Sigmoid mesocolon attaches signoid colon to the
abdominal wall
Note: Anterior layer of transverse mesocolon is adherent
to the posterior layer of the greater omentum
Note: duodenum (second part onwards), ascending and
descending colon are secondarily retroperitoneal; having
fused to the posterior abdominal wall, they are not
suspended by mesocolons.
Supra- and infracolic compartments
•
•
•
Transverse mesocolon divides abdominal cavity into
supracolic and infracolic compartments
Infracolic compartment is divided into right and left
spaces by the small intestinal mesentry.
Communication between supracolic & infracolic
compartments occurs through the paracolic gutters
lateral to the transverse mesocolon
Clinical notes
•
•
•
•
Disease and tumours may spread between organs within the peritoneal cavity
Peritoneal dialysis employs the large surface area of the peritoneal cavity. Dialysis fluid
is injected into the peritoneal cavity, allowing exchange of substances cross the
peritoneum, and fluid is drained after dialysis is complete
Ascites is an excess of fluid in the peritoneal cavity.
Damage or infection to the peritoneum results in peritonitis, making surfaces sticky
with fibrin. Adhesions may form between adjacent layers of peritoneum, limiting
normal movements of the viscera, causing pain, and intestinal obstruction if the
intestine becomes twisted around an adhesion (volvulus)
!
!
NIGEL FONG 2011/2012
PAGE A161
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Summary
Ligaments, mesentries, retroperitoneal organs (minus kidneys), and location of key spaces:
!
!
NIGEL FONG 2011/2012
PAGE A162
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
B. ORGANS OF THE GUT TUBE
!
!
Stomach
LOC
STR
FUNC
BLOOD
NERVE
CLIN
!
!
Epigastric and left hypochondrium regions. Pyloric orifice is at transpyloric plane (L1)
Cardial orifice: pos to 7th L costal cartilage (T11), 2-4cm fr median plane
ANT
Diaphragm, left lobe of liver, ant abdominal wall
POS
Omental bursa, spleen, left kidney & adrenal, pancreas (retroperitonial organs)
Splenic artery, portal vein, aorta & branches, inf vena cava
INF
Pancreas, transverse colon, duodenum
• J-shaped dilation of GI tract between esophagus and duodenum.
• L border = greater curvature, R border = lesser curvature (w angular incisura)
• Parts - Cardia: Surrounding opening of esophagus, creating the cardiac notch
- Fundus: Area above level of cardial orifice
- Body: largest region
- Pyloric part: pyloric antrum & canal. Pyloric sphincter surr pyloric orifice.
• Internally, mucosa forms rugae (longitudinal folds), draining fluids twds pylorus.
Rugae disappear when stomach is filled
• Chemical & mechanical digestion of food (see histology)
• Storage reservoir for food (capable of considerable expansion)
ART
• Following lesser curvature: gastric art – L (fr celiac trunk) & R (fr hepatic
art) branches which anastomose
• Following greater curvature: gastro-omental (gastro-epiploic) art – L (fr
splenic art) & R (fr gastroduodenal art) branches which anastomose
• Short gastric art: supply fundus (highly variable)
VEN
Follow the arteries, emptying into the portal system
LYM
• Gastric lymph nodes along lesser curvature, gastro-omental nodes along greater
• Sup & inf pyloric nodes near the pylorus
• Pancreaticoduodenal nodes at short gastric & splenic art
All drainage eventually twds celiac nodes
PAR
Ant vagal trunk (fr L vagus) & Pos vagal trunk (fr R vagus) on pos surf
SYM
Greater splanchnic n (T6-T9)
Perforation of stomach (e.g. due to ulcer or cancer) endangers surrounding structures with
acidic contents. Erosion of splenic artery can result in severe hemorrhage
NIGEL FONG 2011/2012
PAGE A163
M1 NOTES IN GROSS ANATOMY
!
6 | ABDOMEN
Duodenum
!
!
1st PART
2nd PART
3rd PART
4th PART
!
[Superior part / Ampulla / Duodenal cap] Fr pylorus, running horiz at L1 level
ANT
Quadrate lobe of liver, gallbladder
POS
Lesser sac, gastro-duodenal art, bile duct, portal vein, inf vena cava
SUP
Epiploic foramen
INF
Head of pancreas
[Descending part] Runs vert downward in front of hilum of R kidney.
Bile duct and main pancreatic duct empty into the maj duodenal papilla (med side)
Accessory pancreatic duct (if present) opens into min duodenal papilla (higher up)
ANT
Fundus of gallbladder
POS
Hilum of R kidney, R ureter
LAT
Ascending colon, R colic flexure, R lobe of liver
MED
Head of pancreas, bile duct, main pancreatic duct
[Inferior / horizontal part] Runs horiz to L at L3 level
ANT
Sup mesentric vessels, mesentry of small intestine, jejunum
POS
R ureter, R psoas, inf vena cava, aorta
SUP
Head of pancreas (C-shaped loop of duodenum intimate with pancreas)
INF
Jejunum
[Ascending part] Runs upwards to the duodenojejunal flexure (held in position by
ligament of Treitz, which attaches to the right crus of diaphragm)
ANT
Jejunum, root of mesentry of small intestine
POS
Left margin of aorta, medial border of L psoas
!
NIGEL FONG 2011/2012
!
PAGE A164
M1 NOTES IN GROSS ANATOMY
BLOOD
NERVE
CLIN
6 | ABDOMEN
ART
Sup pancreaticoduodenal art (fr gastroduodenal art), anastomosing with
Inf pancreaticoduodenal art (fr sup mesenteric art)
VEN
Parallels arterial supply
LYM
Via pancreaticoduodenal nodes to gastroduodenal nodes to celiac nodes
Via pancreaticoduodenal nodes to sup mesentric nodes
PAR
Vagus n, via celiac & sup mesenteric plexus
SYM
Greater & lesser splanchnic n, via celiac & sup mesenteric plexus
Duodenal ulcers due to acid chyme squirted into 1st part of duodenum
• Pos ulcers: erode the gastroduodenal artery, producing torrential hemorrhage.
• Ant ulcers: Erode into peritoneal cavity, causing peritonitis and adhesions.
• A perforated ant ulcer results in fluid drainage down the R paracolic gutter into the
R iliac fossa; this may be confused with a perforated appendix
Jejunum & Ileum
!
LOC
From duodenojejunal flexure to ileocecal junction
Jejunum mostly in L upper quadrant, ileum mostly in R lower quadrant
STR
A 6-7m long tube, no clear distinction btw jejunum and ileum
Attached to pos abdominal wall by the mesentry (which has an oblique root)
FUNC
BLOOD
Digestion & absorption of food substances
ART
Jejunal & Ileal arteries, from sup mesenteric art
Forms arterial arcades & vasa recta
NERVE
CLIN
VEN
Corresponding to arteries, draining into sup mesenteric vein
LYM
Lacteals drain to sup mesenteric nodes
PAR
Pos vagal trunk – Peristalsis & Secretion
SYM
Fr T8-T10, via splanchnic n, celiac & sup mesenteric ganglia - ↓ peristalsis/diges.
Intestines are not sensitive to most pain stimuli (cutting/burning) but sensitive to
distension that is perceived as colic (“intestinal cramps”)
Occlusion of art supply results in ischemia, necrosis, and paralytic ileus (obstruction). This
brings severe colic, vomiting, and often fever and dehydration.
NIGEL FONG 2011/2012
PAGE A165
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
External features: jejunum vs ileum
•
•
•
•
!
General features: location
Jejunum is wider and thicker-walled than ileum due to
more numerous plicae circulares
Ileum has more extensive arterial arcades and shorter vasa
recta than jejunum
Ileum has more fat than jejunum: in the jejunum: fat is
deposited mainly near the root while in the ileum fat is
deposited throughout from the root to the intestinal wall.
Large intestine
CECUM
ASC
COLON
TRANSV
COLON
DESC
COLON
SIGMOID
COLON
Blind-ended pouch (6cm) in R iliac fossa
Ileum enters large intestine through ileocecal valve (2-lip) at junc of cecum w asc colon
ANT
Small intestine, greater omentum, ant abd wall
POS
Iliopsoas, femoral nerve, lat cut n of thigh, appendix (often behind cecum)
MED
Appendix
Secondarily retroperitoneal ascension fr cecum to R colic (hepatic) flexure (13cm),
where it turns left and continues as the transverse colon.
ANT
Small intestine, greater omentum, ant abd wall
POS
Iliacus, iliac crest, lower pole of R kidney, iliohypogastric & ilioinguinal n
LAT
R paracolic gutter
Hangs downwards in the umbilical & hypogastric region, btw
•
•
•
•
R colic (hepatic) flexure below the liver
L colic (splenic) flexure below the spleen [rib 9/10] – higher than R colic flexure
Suspended from diaphragm via phrenicocolic lig at splenic flexure
Connected to pos abdominal wall via transverse mesocolon
ANT
Greater omentum, ant abd wall
POS
Duodenum (2nd part), head of pancreas, jejunum & ileum
INF
Pos layer of greater omentum attached to inf border
Secondarily retroperitoneal descent fr L colic flexure to pelvic brim (25cm), continuing as
sigmoid colon
ANT
Small intestine, greater omentum, ant abd wall
POS
Iliopsoas, iliac crest, lat border of L kidney
Iliohypogastric & ilioinguinal n, femoral nerve, lat cut n of thigh
LAT
R paracolic gutter
S-shaped loop fr descending colon to rectum (25-38cm)
Attached to pelvic wall by sigmoid mesocolon
Tenia coli terminate at the rectum
ANT
M: Urinary bladder | F: pos surf of uterus & upper vagina
POS
Rectum & Sacrum, trminal part of ileum
NIGEL FONG 2011/2012
PAGE A166
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
!
BLOOD
NERVE
CLIN
MIDGUT DERV
(Cecum to prox 2/3 transverse colon)
HINDUT DERV
(Distal 1/3 transverse colon to 1/2 anus)
ART
Sup mesenteric art, then
• Ileocolic art: cecum
• R colic art: asc colon
• Middle colic art: transverse colon
Inf mesenteric art, then
• L colic art: desc colon
• Sigmoid art: sigmoid colon
Anastomosis via marginal art
VEN
Follows art ss, draining into portal
Follows art ss, draining into portal
LYM
To sup mesenteric nodes
To inf mesenteric nodes
PAR
Vagus n via sup mesenteric plexus
Fr pelvic splanchnic n (S2-S4)
(sacral parasympathetic n)
SYM
Fr sup mesenteric plexus
Pain fibres follow sympathetic n
Fr lumbar part of sympathetic trunk
via lumbar splanchnic n.
• Colonoscopy allows examination of the colon, biopsy, and polyp removal
• Volvulus (twisting) of the mobile loop of sigmoid colon results in obstruction,
constipation, and ischemia
• Diverticulosis: outpocketings of colon mucosa occur along weak points of muscle
fibres (btw teniae coli). Diverticula can get infected and rupture (diverticulitis), or
erode the nutrient arteries leading to hemorrhage
!
NIGEL FONG 2011/2012
PAGE A167
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
External features: small intestine vs large intestine
•
•
•
General features: size, location, mesentery
Distinguishing features of small intestine:
- Plicae circulares, permanent fold in the mucous membrane of the small intestine,
are visible on the internal surface or via imaging (appears feathery)
Distinguishing features of large intestine:
- Teniae coli: 3 thickened smooth muscle bands representing the longitudinal layer
of muscularis externa
- Haustra (sacculations): Tonic contraction of teniae coli shortens the colon wall
- Appendices epiploicae (omental appendices): small fatty tags attached to wall
Appendix
LOC
Attached to base of posteromedial surf of cecum
Attached to mesentry of small intestine by the mesoappendix
Surf marking: base of appendix is located at McBurney’s point: junc of lat 1/3 and med
2/3 of a line connecting the R ant sup iliac spine to the umbilicus.
Int marking: teniae coli of cecum converge at the base of the appendix
STR
Narrow blind-ended tube (8-13cm) containing a large amt of lymphoid tissue
Tip of appendix may be found in multiple positions, most commonly hanging down into the
pelvis against R pelvic wall, or coiled up behind the cecum
FUNC
BLOOD
NERVE
CLIN
!
Unknown
ART
Appendicular art (via mesoappendix), fr ileocolic art, fr sup mesenteric art
VEN
Appendicular vein
LYM
Sup mesenteric nodes
PAR
Vagus, via sup mesenteric plexus
SYM
Fr T10 sympathetic nerves [see referred pain]
Appendix is predisposed to infection because
• Narrow blind-ended tube, which encourages stasis of large-bowel contents
• Lumen can be obstructed
• Large amt of lymphoid tissue in wall
Appendicitis results in vague referred pain to T10 dermatome over the umbilicus (see n ss),
but pain later localizes over where the inflamed appendix irritates the parietal peritoneum
Perforation of the appendix results in infection of the peritoneum of the greater sac.
NIGEL FONG 2011/2012
PAGE A168
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
C. ACCESSORY ORGANS OF THE GIT
Spleen
!
!
LOC
STR
FUNC
BLOOD
NERVE
CLIN
L hypochondrium, beneath the thoracic cage
Surface marking: follows contour of rib 10 (between 9-11) pos to midaxillary line
ANT
Stomach (via gatrosplenic lig), tail of pancreas
POS
L diaphragm, ribs 9-11, separated from lungs by costodiaphragmatic recess
INF
L colic flexture
MED
L kidney (via splenorenal lig)
•
•
•
•
•
•
•
Mnemonic: 1 inch thick, 3 inch wide, 5 inch long, 7 ounce in weight, btw 9th & 11th rib
Surr by peritoneum except at the hilum (where splenic artery/vein enters/leaves)
Oval shaped, convex diaphragmatic surface opposite the hilum
Sharp and notched ant & sup borders, smooth pos & inf borders
Lymphatic organ: lymphocyte proliferation, immune response
Destroys expended red blood cells (hematopoiesis in the fetus)
Blood reservoir
ART
Splenic art
VEN
Splenic vein (to sup mesentric vein and then portal vein)
LYM
Pancreaticosplenic nodes along splenic art, then to celiac nodes
Fr celiac plexus, accompanying splenic art
• Spleen is the most frequently injured abdominal organ. Rib fracture or sudden marked
increase in intra-abdominal pressure (e.g. blunt trauma to abdomen) can cause rupture
of spleen intraperitoneal hemorrhage, and shock
• Spleen is normally not palpable unless there is splenomegaly (eg due to lymphoma,
granulocytic leukemia, hemolytic anemia, portal hypertension or hypertension)
• Spleen is not a vital organ to sustain life and can be removed (splenectomy) without
much harm because most of its functions are assumed by other reticuloendothelial
organs (liver and bone marrow)
• There may be accessory spleens
NIGEL FONG 2011/2012
PAGE A169
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Liver
LOC
R hypochondrium & epigastric regions (extends into L hypochondrium)
Protected by thoracic cage (ribs 7-11) & moves with respiration.
Relations of ant/sup/pos diaphragmatic surface, posteroinf visceral surface:
DIA
• Diaphragm (bare area of liver directly rests on diaphragm)
• Subphrenic recess seperates liver from diaphragm
• R/L costal margins, pleura, lungs, xiphoid process
VIS
• Sup duodenum, stomach (gastric/pyloric areas), inf vena cava, gallbladder, R
colic flexture & transverse colon, R kidney/adrenals
• Hepatorenal recess seperates R lobe of liver fr R kidney/adrenals
• Lesser omentum lies inferior to L lobe of liver
STR
• Wedge shaped, Soft, smooth, pliable
• Smooth dome-shaped diaphragmatic surf, flat visceral surf (note H shape)
• Covered w visceral peritoneum except at bare area, gallbladder fossa, and porta
hepatitis (where portal triad enters the liver)
• L/R anatomical lobes divided by falciform lig (R is larger)
• R anatomical lobe includes 2 smaller lobes visible on visceral surf
- Caudate lobe* (sup/pos) bounded by lig venosum & IVC
- Qudrate lobe (inf/ant) bounded by gallbladder & ligamentum teres
• Anatomical lobes do not correspond to the 3 functional lobes (R/L/caudate), each of
which is separately SS by hepatic artery, portal vein, and drained by a hepatic duct
LIGS
• Ant(sup) & pos (inf) coronary ligament (cresent shape) & R/L triangular
ligament mark the boundaries of the bare area
• Falciform lig: fr liver to ant abdominal wall
• Round ligament of liver (lig. teres hepatitis) on vis surf: remnant of umbilical vein
• Ligamentum venosum on vis surf: remnant of ductus venosus (fetal shunt to IVC)
• Hepatogastric & hepatoduodenal ligs, forming lesser omentum (fr dorsal mesentry)
FUNC
BLOOD
• Bile secretion for emulsification of fat
• Metabolism of absorbed food (conveyed to liver by portal veins) & detoxification
ART
NIGEL FONG 2011/2012
Hepatic art (fr common hepatic art, celiac trunk) carries oxygenated blood (30%).
Portal vein (70%) carries deoxygenated blood & nutrients from GIT. All venous
drainage from the GIT passes through the liver
PAGE A170
M1 NOTES IN GROSS ANATOMY
NERVE
CLIN
6 | ABDOMEN
VEN
Hepatic veins, draining into the inf vena cava
LYM
Liver is a major lymph-producing organ.
• Hepatic nodes along hepatic vessels, then celiac nodes, cisterna chyli
• Phrenic nodes, then pos mediastinal nodes, etc.
PAR
Vagus nerves (via celiac ganglion) – function uncertain
SYM
Greater splanchnic nerve (via celiac ganglion) – vasomotor
• Normally not palpable except w hepatomegaly – due to heart failure, hepatitis, tumour
• Runner’s stitch may be due to higher central venous pressure triggering hepatomegaly
and stretching the liver’s fibrous capsule.
• Hepatic cirrhosis results in progressive destruction of hepatocytes and replacement by
fat / fibrous tissue, appearing shrunken and nodular (due to contractile effect of
fibrous replacement). This may result due to industrial solvents or chronic alcoholism.
• Liver biopsy: insert needle through R 8/9 intercostal space in midaxillary line in full
expiration.
Billary Ducts
•
R/L hepatic ducts drain the R/L parts of the liver,
uniting to form the common hepatic duct.
•
Union of the cystic duct and common hepatic duct in
the free edge of the lesser omentum (hepatoduodenal
lig) gives the bile duct (pos to duodenum & pancreas)
•
Bile duct then joins the main pancreatic duct to form
the hepatopancreatic ampulla, which opens into the
duodenum thru the major duodenal papilla.
•
Contraction of the sphincter of bile duct (ductus
choledochus) at its distal end results in bile backing up
along the cystic duct to gallbladder for storage.
!
Gallbladder
LOC
Fossa for the gallbladder on visceral surface of liver
Ant to sup part of duodenum (9th costal c, midclav line)
STR
Pear-shaped organ, 50ml in volume
• Fundus: blunt end projecting fr inf border of liver
• Body: main portion
• Neck: tapering end directed twd porta hepatitis
FUNC
BLOOD
NERVE
CLIN
Storage and concentration of bile
ART
Cystic artery (fr R hepatic artery)
VEN
Cystic veins (to hepatic portal vein)
LYM
Hepatic lymph nodes, then celiac lymph nodes
PAR
Vagus n (fr celiac plexus) – causes gallbladder contraction & sphincter relaxation
SYM
From celiac plexus
Gallstones (cholelithiasis) are cholesterol crystals. 50% of gallstones are asymptomatic;
producing pain (biliary colic) when they are large enough to mechanically injure the
gallbladder, or lodge in the hepatopancreatic ampulla, hepatic or cystic duct
NIGEL FONG 2011/2012
PAGE A171
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Pancreas
LOC
STR
!
Epigastrium & left hypochondrium (crossing transpyloric plane)
Retroperitoneal, lies on bodies of L1 & L2 vertebra on posterior abdominal wall
ANT
Transverse colon, lesser sac, stomach
POS
Bile duct, portal (& splenic) vein, inf vena cava, aorta, left kidney & adrenal
L
Hilum of spleen
R
C-shaped curvature of duodenum
Elongated str w lobulated appearance.
• Head: disc shape, lies within concavity of duodenum (ucinate process ext to the left)
• Neck: constricted portion connecting head to body (ant to aorta)
• Body: triangular str running upwards and to the left across midline
• Tail: Runs in the splenicorenal lig and contacts hilum of spleen
Main pancreatic duct begins in tail and runs the length of the gland, opening into the 2nd
part of the duodenum with the bile duct in the major duodenal papilla
An accessory duct may drain into the minor duodenal papilla
FUNC
BLOOD
NERVE
CLIN
• Exocrine: Digestive enzymes and bicarbonate solution to neutralize stomach acid
• Endocrine (Islets of Langerhans): insulin and glucagon production.
ART
Splenic & sup/inf pancreaticoduodenal art
VEN
Splenic & sup/inf pancreaticoduodenal vein
LYM
To celiac & sup mesentric nodes
PAR
From vagus
SYM
From celiac plexus & sup mesenteric plexus
• Rupture of pancreas allows pancreatic juice to digest surrounding tissues
• Pancreatic cancer may compress adjacent structures, eg leading to obstructive jaundice
NIGEL FONG 2011/2012
PAGE A172
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
D. RADIOGRAPHIC ANATOMY OF ABDOMINAL VISCERA
!
Imaging of hollow organs
•
•
Plain X-ray: initial screening
Contrast X-ray: real time X-rays following radioopaque media
-
•
Barium (BaSO4) swallow or enema
Gastrograffin used to exclude leak e.g. post surgery (leakage of barium into
mediastinum / peritoneum can result in mediastinitis / peritonitis and death)
Endoscopy
•
- Via either end of the GIT, but jejunum & Ileum difficult to endoscope
- Colonoscopy fails to show entire colon in 5% of cases due to difficulty reaching RHS
- Advantage: Can biopsy lesions, can do clo test for H pylori
Angiography to show vessels
•
CT scan
-
•
most definitive for tumour staging, metastases, lymph node involvement,
confirmation of appendicitis. Allows evaluation of organs outside the GIT
MRI: most definitive, safest, most expensive
Esophagus
REG
Esophagus
MODE
Barium swallow X-ray
COND
L, C: Normal
R: Upper esophageal
narrowing
VIS
L: Diaphragm & pylorus
C: Peristaltic waves of fluid
R: Narrowing
NOTE
REG
Esophagus
MODE
L: Barium swallow, X-ray
R: CT
COND
Tumour
VIS
Mass impacting on
esophagus, narrowing lumen
NOTE
Esophageal cancer common
in smokers and people who
drink hot tea.
Need to resect with gastric
pull-through
!
NIGEL FONG 2011/2012
PAGE A173
M1 NOTES IN GROSS ANATOMY
Stomach
6 | ABDOMEN
REG
Stomach
MODE
Gastrograffin swallow
COND
Tumour
VIS
Non-smooth borders
NOTE
Gastric bubble may be visible
at the air-fluid level in the
fundus.
Peristaltic waves are also
commonly visible
!
REG
Stomach
MODE
CT
COND
Tumour
VIS
Borders of stomach are not
smooth
NOTE
Small intestine
REG
Small intestine
MODE
Barium / gastrograffin
follow-through
COND
Small bowel obstruction
Dilation & adhesions of small
intestine
VIS
Note: plicae circulares and
location identifies this as
small intestine
NOTE
Clinical sighs: vomiting,
failure to defecate,
intermittant abdominal pain.
Small bowel obstruction:
fluid levels visible
NIGEL FONG 2011/2012
PAGE A174
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Large intestine
REG
Large intestine
MODE
Barium enema
COND
Normal
VIS
Haustration and location
identifies this as large
intestine
NOTE
A double contrast of air &
barium may be done for
better visualization
REG
Large intestine
MODE
Barium enema
COND
Apple core lesion
VIS
Sharply defined annular
constricting colonic
narrowing, resembling an
apple core (after the sides
have been bitten away)
NOTE
Often indicative of cancer
May also be seen in
esophagus
REG
Large intestine
MODE
CT, transverse
COND
Incidental colonic mass
(possible carcinoma)
VIS
Normal fecal material
appears bubbly
!
!
Suspicious solid mass in L
iliac fossa (arrow)
NOTE
!
!
NIGEL FONG 2011/2012
Renal carcinoma is quite
common. PR bleeding should
prompt scan
!
PAGE A175
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
!
REG
Large intestine
MODE
Gastrograffin enema
COND
Leakage from surgical suture
VIS
Gastrograffin dye leaks out of
the colon from the LHS
NOTE
Gastrograffin enema done to
exclude leak post-surgery
REG
Large intestine
MODE
CT colonography, 3D
reconstruction
COND
Polyp detection
VIS
Obstruction of colon
Software can calculate
dimensions.
NOTE
Challenge is to differentiate
fecal material vs tumour:
Bowel preparation or fecal
tagging necessary, need to
reconstruct prone and supine
images if difficult to see.
!
PR foley’s catheter and
pump air for visualization
!
!
Liver
REG
Liver
MODE
CT, reconstructed
COND
Normal
VIS
Analysis of liver vasculature
and lobes
NOTE
Analysis in preparation for
surgical resection for liver
donation
!
NIGEL FONG 2011/2012
PAGE A176
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
REG
Liver
MODE
MRI
[Top] T1 weighted seq
[Bottom] T2 weighted seq
COND
Normal
VIS
Portal vein and tributaries
NOTE
T1 W: fluid appears dark
T2 W: fluid appears bright
To distinguish T1/T2, check
for whether CSF appears
dark or light
!
Pancreas
REG
Pancreas
MODE
Ultrasound
COND
Normal
VIS
Top to bottom (probe top):
- Skin, fascia, muscle
- L lobe of liver
- Collapsed stomach (empty)
- Pancreas (arrow)
- Splenic vein
NOTE
!
!
NIGEL FONG 2011/2012
PAGE A177
M1 NOTES IN GROSS ANATOMY
!
6 | ABDOMEN
Gall bladder
REG
Gallbladder
MODE
MR cholangiography
(MRCP)
COND
Gall stones
VIS
Dilated common bile duct
due to presence of small
gallstone
Pancreatic duct goes to side
NOTE
!
REG
Gallbladder
MODE
Endoscopic retrograde
cholangiography (ERCP)
COND
Gall stones
VIS
Gall stones (radiolucent)
Catheter
Dilated bile duct
NOTE
ERCP seldom done for
imaging anatomy.
Therapeutic: catheter to
balloon & pull out stone.
!
!
Spleen
REG
Abdomen, axial section
MODE
CT
COND
Lymphoma
VIS
Splenomegaly
Enlarged lymph nodes
NOTE
NIGEL FONG 2011/2012
PAGE A178
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
REG
Abdomen / Chest
MODE
P-A X-ray
COND
Perforation of bowel
VIS
Air under diaphragm
Thin-walled unlike gastric
bubble
NOTE
Surgical emergency if
perforation of bowel
Normal in post-operative
patient (peritoneum closed
with air inside), or in
peritoneal dialysis pt
!
NIGEL FONG 2011/2012
PAGE A179
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
4. NEUROVASCULAR SUPPLY OF ABDOMINAL VISCERA
General ideas - Ref embryology
A. ARTERIAL SUPPLY OF THE GUT
!
Celiac trunk
!
ORIGIN
COURSE
L GASTRIC
SPLENIC
Abdominal aorta (at T12)
Very short; splits into the L gastric, splenic, and hepatic arteries
Runs to the stomach cardia, gives off esophageal branches, and turns right to travel
along the lesser curvature of stomach to anastomose with the R gatric artery
Wavy leftward course along the upper border of pancreas, entering hilum of spleen
• Pancreatic branches
• L gastroepiploic art: arise near hilum of spleen, follows greater curvature of
stomach, anastomose w R gastroepiploic
• Short gastric art (5-6): supply fundus of stomach
HEPATIC
Common hepatic artery: runs forward and to the right
• R gastric artery: arises at R border of pylorus, runs left along the lesser
curvature of stomach to anastomose with L gastric artery
• Gastroduodenal art: Desc behind 1st part of duodenum, dividing into
- R gastroepiploic art: runs along greater curvature of stomach to anastomose w L
gastroepiploic art
- Sup pancreaticoduodenal art: Desc btw duodenum (2nd part) & pancreas head
The common hepatic artery then ascends to the liver in the free edge of the lesser
omentum as the hepatic artery proper, splitting into R and L hepatic arteries, and
cystic artery supplying the gallbladder
SS
NOTES
!
Derivatives of the foregut: distal 1/3 esophagus up to middle of 2nd part of duodenum
There is no corresponding ‘celiac vein’ The corresponding vein is the splenic vein.
Distinguishing splenic vein vs splenic artery: splenic artery is torturous and more sup
NIGEL FONG 2011/2012
PAGE A180
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
!
REG
Celiac trunk
MODE
Angiogram
COND
Normal
VIS
The expected branches of the
celiac trunk
NOTE
Splenic artery follows
tortuous corse
!!
!
Superior mesenteric artery
ORIGIN
COURSE
BRANCH
TERM
SS
CLIN
Abdominal aorta, just below the celiac trunk (L1)
Runs inferiorly and to the right behind the neck of the pancreas and in front of the 3rd
part of duodenum. Continues towards small intestine through the mesentery
• Inf pancreaticoduodenal art: supplying duodenum and head of pancreas,
anastomosing with sup pancreaticoduodenal art.
• Middle colic art: to transverse colon
• R colic art: to ascending colon
• Ileocolic art: downwards and rightwards towards R iliac fossa, giving off
- sup branch anastomoses with R colic art
- inf branch which divides into colic, cecal, appendicular, ileal br
• Jejunal & ileal branches: which form arterial arcades & vasa recta
Derivatives of midgut: From 2nd part of duodenum to prox 2/3 of transverse colon
• Hernia can strangulate blood supply, resulting in infarction of the bowel.
• It is important to exclude embolism of the mesenteric arteries in unexplained
abdominal pain.
NIGEL FONG 2011/2012
PAGE A181
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
REG
Celiac trunk, SMA
MODE
CT, 3D reconstructed
Arterial phase enhanced
COND
Normal
VIS
Arterial vasculature
NOTE
Arterial phase enhanced:
inject contrast and then scan
immediately while dye
remains in arteries.
Venous phase enhanced: wait
a while for dye to go to veins,
then scan.
Inferior mesenteric artery
ORIGIN
COURSE
BRANCH
TERM
SS
!
Abdominal aorta, below origin of sup mesenteric artery (L3)
Descends ant to aorta and passes left, continuing inferiorly
• L colic art: to distal 1/3 transverse colon, L colic flexure, upper descending colon
• Sigmoid arteries: to descending & sigmoid colon
• Sup rectal art: continuation of inf mesenteric art as it crosses the L common iliac
artery. Descends into pelvis behind the rectum
Derivatives of hindgut: Distal 1/3 of transverse colon to upper half of anal canal
Marginal artery
•
•
Anastomosis of colic arteries around concave margin of the large intestine forms a
single arterial trunk, the marginal artery.
Provides good collateral circulation
• Clinical: May be enlarged e.g. to supply hindgut due to occlusion of inf mesenteric art
NIGEL FONG 2011/2012
PAGE A182
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
B. VENOUS & LYMPHATIC DRAINAGE OF THE GUT
!
Portal Vein
!
!
ORIGIN
!
Forms pos to the neck of pancreas by union of the sup mesenteric and splenic veins (L2),
receiving blood from the tributaries:
• Splenic vein: travels left fr hilum of spleen, passing through splenorenal ligament
with splenic artery and pos to tail of pancreas. In turn receives
- Inferior mesenteric vein: drains to splenic vein
- Short gastric veins
- L gastro-omental veins: fr greater curvature of stomach
- Pancreatic veins
• Sup mesenteric vein: fr veins joining small intestine & cecum, ascends in root of
mesentery of small intestine, passing in front of 3rd part of duodenum. In turn
receives
- R gastro-omental vein: fr greater curvature of stomach
- Inf pancreaticoduodenal veins
COURSE
Ascends behind 1st part of duodenum, passing through the free edge of lesser omentum
(hepatoduodenal lig) ant to omental foramen and pos to bile duct & hepatic portal.
Directly receives blood from
• R/L gastric veins: fr lesser curvature of stomach
• Cystic veins: fr gallbladder
• Para-umbilical veins
TERM
DRAINS
Divides into R/L branches which enter the liver parenchyma
All blood from the GIT
!
NIGEL FONG 2011/2012
!
PAGE A183
M1 NOTES IN GROSS ANATOMY
CLINICAL
6 | ABDOMEN
Portal hypertension may arise from liver cirrhosis, increasing bloodflow through
portal-systemic anastomoses, producing venous enlargement:
• Esophageal varices: dilated veins comm. btw esophageal branches of L gastric vein
(portal) and esophageal veins from azygos veins (systemic), which may rupture and
cause hemorrhage
• Caput medusae: varicose, snake-like veins radiating from umbilicus – comm btw
sup veins of ant abd wall (superficial) and paraumbilical veins (travelling in the
falciform ligament accompanying ligamentum teres to join the portal vein)
• Hemorrhoids: Anastomosis btw sup rectal veins (portal) & inf rectal veins
(systemic) draining the sup & inf 1/2 of the anal canal respectively
Porto-systemic shunts may be created to reduce portal hypertension by diverting
blood from the portal system to the systemic veins.
!
!!!!!!!!!
!
Lymphatics
•
•
Lympatic drainage from GIT follows arterial supply, ending up in pre-aortic lymph
nodes at the origins of the celiac, superior mesenteric, and inferior mesenteric arteries
Lymph eventually drains into the cisterna chyli and enter the thoracic duct
NIGEL FONG 2011/2012
PAGE A184
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
C. NERVE SUPPLY OF THE GUT
!
Nervous function
•
•
Parasympathetic: visceromotor (drives peristalsis, secretion), resp for visceral reflex
Sympathetic: vasoconstriction, inhibit peristalsis & digestion
•
•
Abdominal prevertebral plexus form fr both sympathetic and parasympathetic fibres.
Enteric nervous system is a local neuronal circuit in the GI wall, consisting of
-
!
Myenteric (Auerbach) plexus: btw layers of muscularis externa
Submucosa (Meissner’s) plexus: in the submucosa
Regulates and coordinating GIT secretion and peristalsis
Parasympathetic & sympathetic signals regulate and can override the enteric sys.
Parasympathetic innervation
•
Ant/pos vagal trunks (presynaptic)
•
- Cont. of L/R vagus emerging fr esophageal plexus (pass through esophageal hiatus)
- Supply foregut & midgut derivatives (up to prox 2/3 of transverse colon)
Pelvic splanchnic nerves (presynaptic)
•
•
- Derive directly fr ant rami of S2-S4
- The only splanchnic nerve containing parasympathetic fibres
Terminate onto scattered postsynaptic neurons lying on or within abdominal viscera.
Function: visceromotor, visceral reflex
NIGEL FONG 2011/2012
PAGE A185
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Sympathetic innervation
•
Splanchnic nerves (presynaptic), fr intemedio-lateral horns
•
- Greater splanchnic nerve (T5-T9)
- Lesser splanchnic nerve (T10-T11)
- Least splanchnic nerve (T12)
- Lumbar splanchnic n (L1-L2/L3)
Terminate onto postsynaptic neurons
– celiac ganglia
– sup mesenteric ganglia
– aorticorenal ganglia
– inter- / inf mesenteric, sup hypogastric plexus
in the ganglia.
Pain afferents
•
•
•
GIT is sensitive to distention, chemical toxins,
etc (but not touch/pressure)
Pain afferents generally accompany sympathetic
- Foregut: T6-T9
| Dermatome: Epigastric
- Midgut: T8-T12 | Dermatome: Umbilical
- Hindgut: T12-L2 | Dermatome: Hypogastric
Hence the pain from appendicitis is initially
referred to the umbilical region
!
!
NIGEL FONG 2011/2012
!
PAGE A186
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
5. DEVELOPMENT OF THE URINARY SYSTEM
A. DEVELOPMENT OF KIDNEYS
!
!
!
The 3 nephros
•
•
•
Kidneys develop from intermediate mesoderm along posterior wall of abdominal cavity
(Urogenital ridge – forms gonads & urinary system)
3 different kidney systems form in cranial-caudal sequence.
Cranial cell groups / tubules of pronephros & mesonephros degnerate while caudal
portions are still differentiating.
!
PRONEPHROS
MESONEPHROS
METANEPHROS
FORMS
Start of 4 week
4 week
5th week
DEGENS
End of 4th week
End of 2nd month
-
REGION
Cervical
Upper thoracic to L3
Pelvic
STR
Nephrotomes, 7-10
solid cell groups
Large ovoid organ on each side of
midline (gonad medial), forms
urogenital ridge. Tubules open
into bilateral mesonephric ducts,
which opens into cloaca
Collecting sys dvp fr
uretric bud, a diverticulum
of the mesonephric duct.
Nephrons dvp fr intem.
mesoderm like mesonephros
FUNC
Non-functional
Short func in early fetus
Permanent kidney
th
th
!
NIGEL FONG 2011/2012
PAGE A187
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Uniferous tubule development
•
Ureteric bud (diverticulum of mesonephric duct) penetrates metanephric tissue
•
Ureteric bud forms the collecting system: dilates to form renal pelvis and branches
repeatedly to give the ureter, renal pelvis, major/minor calyces, and collecting tubules.
Metanephric tissue cap is induced by the collecting tubule to form, in turn, renal
vesicles (4), comma-shaped body (5), S-shaped body (6), and metanephric tubules (7).
Metanephric tubule: proximal end forms Bowman’s capsule, distal end connects to
collecting tubules.
Middle segment of nephron lengthen to form convoluted tubules & loop of Henle (8)
Approx 1mil nephrons at birth, no further nephrons form post natally
Kidneys lobulated at birth, further nephron growth gives a bean shape.
•
•
•
•
•
1
!
2
3
4
5
6
7
8
Yellow = From ureteric bud | Pink = From metanephric tissue cap (intemediate mesoderm)
Ascent of kidneys
•
•
•
Kidneys initially located in pelvic region but shifts cranially into the abdomen due to
diminution of body curvature and lumbosacral growth.
Initial blood supply from pelvic branch of aorta, but they degenerates as the more
cranial renal arteries form from the lumbar region
Kidneys are primarily retroperitoneal, always remaining posterior to the peritoneal
cavity and never intraperitoneal at any stage of development
Fetal function of kidney
•
•
•
Functional at end of 1st trimester
Urine excreted into amniotic cavity, mixes with amniotic fluid & swallowed by fetus to
be reabsorbed through the intestinal tract.
Excretion of waste products is done by the palcenta, not kidney.
!
NIGEL FONG 2011/2012
PAGE A188
M1 NOTES IN GROSS ANATOMY
!
6 | ABDOMEN
Congenital defects
Renal agenesis: ureteric bud
did not contact metanephric
mass, both degenerate
Horseshoe kidney
due to fusion of 2 kidneys
Double kidney. Early
branching of ureteric bud,
separates metanephric mass.
Ureter duplicated.
Other anomalies:
• Ectopic (pelvic) kidney
• Ectopic ureter
Accessory renal arteries that do not degenerate. May constrict
ureter, causing an enlarged renal pelvis and impeding urine outflow
B. DEVELOPMENT OF BLADDER & URETHRA
Urorectal Septum
•
•
Cloaca is the terminal part of the hindgut
Urorectal septum forms btw 4th-7th week, dividing cloaca into pos anorectal canal &
ant urogenital sinus (separated from the outside by the urogenital membrane)
•
Fusion of urorectal septum with cloacal membrane is represented in the adult by the
perineal body
•
Cloacal membrane divided into urogenital membrane & anal membrane.
•
Cloacal sphinter is divided into a posterior part (external anal sphinter) and anterior
parts (superficial transverse perineal, bulbospongiosus, ischiocavernosus muscles), all
supplied by the pudendal nerve
NIGEL FONG 2011/2012
PAGE A189
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Urogenital Sinus
•
•
Forms from endoderm
Upper part (largest) forms the bladder.
-
•
•
Initially continuous with the allantois (vestigial),
Allantois is later obliterated to form the
urachus/uranus (thick fibrous cord), which in adults is
the median umbilical ligament
Clinical: see persistent urachus (pelvis)
!
Pelvic part (narrow canal) forms the prostatic & membranous urethra in males
Definitive/phallic part (flattened) of the urogenital sinus forms rest of the urethra.
Bladder trigone
•
Caudal portions of mesonephric absorbed
into the bladder wall, forming the trigone.
Mucosa of bladder formed thus is
mesodermal in origin even as the rest of
the bladder is endodermal
•
•
Mesodermal lining is replaced by endodermal epithelium with time
Orifices of mesonephric ducts become the vas deferens in males.
•
Urethra
•
•
•
Endodermal origin from urogenital sinus (entirely from urogenital sinus in females)
In males, distal urethra derived from urethral plate
Surrounding connective tissue & smooth muscle from splanchnic mesoderm
!
NIGEL FONG 2011/2012
PAGE A190
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
6. POSTERIOR ABDOMINAL WALL
!
A. POSTERIOR ABDOMINAL VISCERA
!
Kidneys
!
LOC
!
Retroperitoneal, lie on pos abd wall fr T11-L3, 2.5-9cm fr midline (Morris parellogram)
R kidney lower (sup pole ant to T12 rib) than L kidney (sup pole ant to T11-12 rib) due
to presence of liver
R KIDNEY
L KIDNEY
ANT
Liver, hepatorenal recess
2nd part of duodenum, R colic flexure
Spleen, pancreas,
stomach, jejunum, L colic flexure
POS
Diaphragm, costodiaphragmatic recess,
12th rib
Diaphragm, costodiaphragmatic recess,
11th & 12th rib.
3 muscles: psoas maj, quadratus lumborum, transversus abdominis
3 nerves: subcostal (T12), iliohypogastric (L1), ilioinguinal (L1)
MED
STR
•
•
•
•
•
Suprarenal gland
Bean-shaped, 10cm length x 5cm width x 2.5cm thick.
In adult: kidney = 2 vertebral bodies + 1 intervertebral space
In child, kidney = 4 vertebral bodies
Surfaces: ant/pos | Poles: sup/inf | Margins: med (concave) /lat (convex)
Hilum (L1) on medial concave border: renal artery enters, renal vein & ureter leaves
Inner structure
• Dark brown outer cortex, light brown inner medulla.
• The medulla is made up of 8-12 pyramids, each with a deep conical projection
towards the hilum called the renal papillae.
• Each renal papilla opens into a minor calyx, which joins to form major calyces, and
subsequently the renal pelvis, which drains as the ureter.
Coverings support the kidneys. Superficial to deep:
•
•
•
•
NIGEL FONG 2011/2012
Fibrous capsule
Perirenal (perinephric) fat: separate kidney fr suprarenal glands
Renal fascia: encloses kidney & suprarenal glands, cont. with transversalis fascia
Pararenal fat: Often in large quantity
PAGE A191
M1 NOTES IN GROSS ANATOMY
FUNC
BLOOD
6 | ABDOMEN
• Excretion of waste products
• Homeostasis: acid-base balance, volume and osmolarity regulation
• Erythropoietin synthesis etc
ART
Renal arteries:
•
•
•
•
VEN
Arise fr aorta at L2
Div into 5 segmental arteries, then lobar, interlobar, arcuate art (see histo)
Are anatomical end arteries
May have accessory renal art (see embryology)
Renal vein from hilum to inf vena cava
• L renal vein longer than R renal vein
• L renal vein receives L suprarenal & L gonadal vein
• Clinical: A rapidly developing left-sided variocele (dilation of the veins of the
pampiniform plexus fr testes) should always lead one to examine the L kidney.
NERVE
CLIN
LYM
Lateral aortic (lumbar) lymph nodes around origin of renal artery
PAR
Fr renal plexus (less significant)
SYM
Fr T10-T12 (lesser & least splanchnic n, esp T12) via renal plexus
Renal pain referred to flank and anterior abdominal wall (T12 dermatome)
Usual surgical approach through pos abd wall
Nephrotosis: dropped kidney due to insufficient support by renal fascia
Renal fascia is a barrier to spread of infection / tumour btw perirenal & pararenal
spaces.
• Renal vein entrapment syndrome: L renal vein lies in acute angle formed by the
sup mesenteric art & aorta; downward traction on SMA may compress L renal vein,
resulting in left flank pain, hematuria/proteinuria, nausea & vomiting (due to duodenal
compression), and testicular pain (due to L testicular vein draining into L renal vein).
• Renal tumours invading the renal vein may result in dilated L gonadal vein & L
varicocoele
•
•
•
•
!
NIGEL FONG 2011/2012
PAGE A192
M1 NOTES IN GROSS ANATOMY
!
6 | ABDOMEN
Suprarenal (Adrenal) glands
[Vasculature only,
relations are inaccurate]
!
LOC
STR
FUNC
BLOOD
Retroperitoneal, lie on upper pole of kidney
R SUPRARENAL
L SUPRARENAL
ANT
R lobe of liver, inf vena cava
Pancreas, lesser sac, stomach, spleen
POS
Diaphragm
Diaphragm
INF
R kidney
L kidney
Surrounded by renal fascia, separated fr kidney by perirenal fat
Yellow cortex & dark brown medulla
R adrenal: pyramid shape | L adrenal: crescentic shape
Larger than kidneys in neonates (vis on ultrasound), smaller in adults (cannot ultrasound)
Cortex (mesoderm): secrete mineral corticoids & glucocorticoids
Medulla (neural crest): secrete catecholamines (epinephrine, norepinephrine)
ART
3 arteries (branch before entering gland, giving 50-60 branches):
• Sup suprarenal arteries: 6-8 fr inf phrenic artery
• Middle suprarenal artery: fr aorta
• Inf suprarenal artery: fr renal art
VEN
Single vein:
• R suprarenal: fr hilum to inf vena cava
• L suprarenal: fr hilum to renal vein
NERVE
CLIN
LYM
Same as kidneys: Lateral aortic (lumbar) lymph nodes around origin of renal art
SYM
Presynaptic sympathetics fr lesser splanchnic n (T10-T11) go to chromaffin
cells in suprarenal medulla
• Separation of suprarenal gland from kidneys allows for surgical removal of only the
kidney without damage to the suprarenal gland.
NIGEL FONG 2011/2012
PAGE A193
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Ureters
LOC
!
•
•
•
•
•
Emerges fr hilum of kidney
Running vert downward, lying on psoas maj, behind parietal peritoneum
Enters pelvis by crossing bifurcation of common iliac artery in fron of sacroiliac joint
Runs down lat wall of pelvis to ischial spine
Turns fwd to enter bladder at an oblique angle
R URETER
ANT
Crossed anteriorly by gonadal vessels
Duodenum, term ileum, rt of mesentry
R colic & ileocolic vessels,
POS
STR
FUNC
BLOOD
L URETER
Sigmoid colon & mesocolon
L colic vessels
Psoas maj, bifurcation of common iliac art
Muscular tubes (25cm long, like esophagus) with 3 constrictions
• At junction of ureter and renal pelvis
• Where ureters cross brim of pelvic inlet
• Oblique entry into the bladder
Conducts urine from the kidneys to the bladder (aided by peristaltic contractions
ART
3 arteries:
• Sup 1/3: fr renal artery (supplies kidney)
• Middle 1/3: fr gonadal (testicular/ ovarian) artery & aorta
• Inf 1/3: fr superior vesical artery (supplies bladder)
NERVE
CLIN
Resembles
supply of
esophagus
VEN
Parallel arteries
LYM
Same as kidneys: Lateral aortic (lumbar) lymph nodes around origin of renal art
Fr renal, testicular/ovarian, hypogastric plexuses. Sympathetic fr T11-L2
See kidney stones: ureteric pain referred to T11-L2 dermatome (loin to groin)
Close to lat fornix of vagina & lat to cervix: may be affected by local tumour spread,
leading to hydronephrosis (distension of ureter, renal pelvices due to obstruction)
NIGEL FONG 2011/2012
PAGE A194
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Kidney stones
•
•
•
•
Kidney stones (calculi) passing down ureter causes very severe intermittant pain
(ureteric colic) as it is gradually forced down by peristaltic waves.
Loin to groin pain: Pain is referred to T11-L2 dermatomes (infrascapular reg into the
groin), as the visceral pain afferents fr the ureters travel with the sympathetic
nervesupply fr T11-L2. Generalized sympathetic response may result.
Complications: Hematuria, infection, urinary obstruction, and renal failure may result.
Lithotripsy focuses a shockwave to break the stone into small fragments that may
pass out through the urine
!
REG
Kidneys, ureters, bladder
MODE
IV pyelogram
(X-ray taken aft injection of
contrast media)
COND
Ureteric stone L
VIS
Blockage and back up of
urine into the L kidney
(R is normal – not entirely
filled, may see ‘waves’ of
fluid due to peristalsis)
NOTE
Uric acid stones may not be
radio opaque
Source:
http://www.comiterpa.com/hematuria%20
radiologic_studies.htm
NIGEL FONG 2011/2012
REG
Kidneys, ureters, bladder
MODE
CT
COND
3x ureteric calculi
VIS
Ureteric calculi at
- L renal pelvis
- L & R vesicoureter junction
NOTE
Note the 3 narrowings of the
ureters where the kidney
stones are likely to get
trapped: kidney-ureter
junction, pelvic rim, and
vesico-ureter junction
PAGE A195
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
B. DIAPHRAGM
!
!
!
Structure
•
•
•
Double-domed musculotendinous septum separating the the thorax and the abdomen
- Expiration: Right dome reaches upper border of 5th rib (higher due to liver)
- Expiration: Left dome reaches lower border of 5th rib
Chief muscle of inspiration (passively relaxes in expiration)
- Inspiration: ↓ intrathoracic pressure and ↑ intra-abdominal pressure
- This aids venous return from the IVC
- People with dyspnea prefer to sit up, when sitting, diaphragm works with gravity
rather than opposes it.
- Contraction of diaphragm aids ↑ intra-abdominal pressure e.g. in defecation
Peripheral muscular sheet connects to central tendon.
-
Central tendon has no bony attachments, and resembles a cloverleaf
Sup surface partially fused with inferior surface of fibrous pericardium
Origins of muscular parts
•
•
•
Sternal part: attaching to xiphoid process
Costal part: attaching to int surf of inf 6 ribs & costal cartilages
Lumbar part: arises from L1-L3 vertebrae and
- Med arcuate lig: thicking of psoas fascia btw L2 body - L1 transverse proc
-
•
Lat arcuate lig: quadratus lumborum covering btw rib 12 – L12 transverse proc
Crura of diaphragm: musculotendinous bands forming an arch over the aortic hiatus
- R crus arises from L1-L3 & IV discs - longer
-
L crus arises from L1-L2 & IV discs
Crura are connected by the median arcuate ligament
Clinial: Herniation
•
•
•
Rupture of diaphragm and herniation of viscera can result from sudden large increase
in thoracic or intra-abdominal pressure e.g. RTA trauma
- Mostly on L side as the liver provides a physical barrier
Hiatal hernia: protrusion of part of the stomach into the thorax through the
esophageal hiatus
Congenital diaphragmatic hernia – see thorax
NIGEL FONG 2011/2012
PAGE A196
M1 NOTES IN GROSS ANATOMY
!
6 | ABDOMEN
Diaphragmatic apertures & structures passing through
OPENING
LVL
OPENING IN
Caval
opening
T8
Opening in central tendon
(R of midline)
Esophageal
hiatus
T10
Opening in R crus
(L of midline)
Aortic hiatus
T12
Pos to diaphragm (X pierce),
btw crura pos to median
arcuate lig
Pierces diaphragm
Transmitted ant/pos to diaphragm
Blood supply
•
• Inf vena cava: Diaphragm contractn
dilates IVC, ↑ IVC flow against gravity
• R phrenic n
• Esophagus
• A/P vagal trunks
• Esophag. br of L gastric vess; lymphatic
• Aorta
• Thoracic duct
• Azygos / hemiazygos veins (sometimes)
• L phrenic
• Greater & lesser splanchnic n
• Hemiazygos vein (sometimes)
• Sup epigastric vess
• Sympathetic trunks, least splanchnic n
!!!!!
!
Arteries:
- Sup surface: Musculophrenic & pericardiophrenic art (fr int thoracic art)
-
•
•
PASSAGE OF
Sup phrenic art (fr thoracic aorta) on sup surf
Inf phrenic art (fr abdominal aorta) on inf surf
Venous drainage corresponds.
Lymphatics: Ant/pos diaphragmatic nodes on sup surf of diaphragm, draining into
parasternal, pos mediastinal, phrenic nodes.
Nerve supply
•
Motor: ipsilateral R/L phrenic nerves (C3-C5)
•
Sensory:
- Phrenic n: Parietal pleura & peritoneum covering central surfaces of diaphragm
- Lower intercostal n: Peripheral parts
•
Clinical: Referred pain fr central part of diaphragm occurs at the shoulder region
(C3-C5)
NIGEL FONG 2011/2012
PAGE A197
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
C. MUSCLES OF POS ABD WALL
!
!
!
MUSCLE
NERVE
ORIGIN
Psoas maj
L1-L3
ant rami
T12-L5 body sides & IV discs
L1-L5 transverse proc
Iliacus
Femoral
n
Sup 2/3 iliac fossa, ala of
sacrum, ant sacroiliac lig
Quadratus
lumborum
T12-L4
ant rami
Med 1/2 inf border rib 12
L1-L5 Transverse proc
Psoas min
!
INSERTION
Pass under inguinal lig,
attach to lesser
trochanter of femur
Int lip iliac crest
Iliolumbar lig,
ACTION
Lat flex vert column
Flex thigh
Flex thigh
Ext vert column
Lat flex vert column
If present, psoas min is a glistening tendon on surf of psoas maj
Clinical notes
•
•
Iliopsoas test: pain elicited when pt lies on unaffected side and extends thigh of
affected side against resistance of examiner’s hand may indicate disease of structures
related to the ilipsoas: kidneys, ureters, cecum, appendix, sigmoid colon, pancreas,
lumbar nodes, nerves of pos abd wall.
Psoas abscess: TB infection of the IV discs spreads into the psoas sheath, producing
a psoas abscess. The psoas fascia thickens, allowing pus and infection to spread
inferiorly down into the thigh.
!
NIGEL FONG 2011/2012
PAGE A198
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
D. NERVES OF POS ABD WALL
!
!
!
Lumbar plexus
•
•
•
!
Lumbar spinal nerves (L1-L5) pass fr spinal cord through IV foramina inf to corres vert
Lumbar plexus forms in the substance of the psoas maj from ant rami L1-L5
Subcostal n is also visible but this is not part of the lumbar plexus
!
NERVE
LEVEL
COURSE
MOTOR SS
SENSORY SS
Emerge lat to psoas maj, ant to quadratus lumborum, passes inferolaterally [Sup-inf]:
Lower ant abd wall
Posterolat gluteal skin
Iliohypogastric
L1
Courses ant btw
transv abd & int obliq
Ilioinguinal
L1
Through inguinal canal
Lat femoral
cutaneous
L2-L3
Enter thigh behind lat
end of inguinal lig
Femoral
L2-L4
See lower limb
Ant thigh except
psoas maj
Hip, knee, anteromed thigh,
med ankle & foot
Genital branch:
enters spermatic cord
M: Cremasteric
muscle
M: ant scrotum
F: mons pubis, labium maj
Abdominals:
- Int oblique
- transversus abd
Groin, scrotum / labium maj
Lat thigh
Emerge ant to psoas maj:
Genitofemoral
L1-L2
Upper ant thigh
Femoral branch
Emerge med to psoas maj:
Obturator
L2-L4
See lower limb
Med thigh except
pectinus, hamstring
part of add magnus
Medial thigh
!
NIGEL FONG 2011/2012
PAGE A199
M1 NOTES IN GROSS ANATOMY
6 | ABDOMEN
Aortic (prevertebral) plexus
•
•
•
•
•
Forms around abdominal
aorta fr aortic hiatus to
aortic bifurcation
Continues into the pelvis as
sup hypogastric plexus
Subdivisions named aft art:
celiac, renal, sup & inf
mesenteric plexus.
Assc w prevertebral ganglia
(postganglionic sympathetic
cell bodies)
Carries
-
!
Preganglionic & postganglionic sympathetic
Pre-ganglionic parasympathetic (fr Vagus / pelvic splanchnic n)
Visceral afferent fibres
!
Sympathetic trunks
•
•
•
•
Sympathetic
trunks
(fr
thorax) travel on anterolat
aspects of lumbar vertebrae
L1-L2 give white rami
communicans
to
sympathetic trunks
Gray rami communicans
provide sympathetic supply
to lumbar plexus nerves
Lumbar splanchnic n arises
fr med aspect of lumbar
sym trunks
!
!
!
Summary: Referred pain pathways
ORGAN
AFFERENT
LEVEL
PAIN REF TO
CLINICAL
Heart
Thoracic splanchnic n
T1-T4
Upper thorax, med arm
Angina pectoris, MI
Foregut
Greater splanchnic n
T5-T9
Lower thorax, epigastric
Gallstones
Midgut
Lesser splanchnic n
T9-T10
Umbilical reg
Appendicitis
Kidney, ureter
Least splanchnic n
T12
Flanks, pubic reg
Kidney/ureter stones
Hindgut
Lumbar splanchnic n
L1-L2
Flanks, groin, lat/ant
thighs
!
NIGEL FONG 2011/2012
PAGE A200
M1 NOTES IN GROSS ANATOMY
E. VESSELS
!
!
OF
6 | ABDOMEN
POS ABD WALL
Abdominal aorta
!
!
ORIGIN
COURSE
TERM
BR
SS
CLINICAL
!
Begins at aortic hiatus in diaphragm (T12)
Descends retroperitoneally, on ant surf of lumbar vertebrae.
R
IVC, cisterna chyli, azygos vein
L
L sympathetic trunk
ANT
Preaortic plexus & ganglia, body of pancreas, splenic vein, L renal vein.
Divides into R/L common iliac arteries (L4)
Ant unpaired visceral br: Celiac trunk (T12), Sup mesenteric (L1), Inf mesenteric (L3)
Lat paired visceral br: Middle suprarenal art (L1), Renal art (L1), Gonadal art (L2)
Posterolat paired parietal br: Inf phrenic art (T12), 4x lumbar art (L1-L4)
Median sacral art: fr pos surf of aorta just sup to bifurcation.
Blood to pelvis, perineum, lower limbs
Abdominal aortic aneuysm: localized aortic dilation (pulsatile on deep palpation) may
result from atherosclerosis, causing weakening of the arterial walls. As these may rupture
and result in hemorrage with 90% mortality, they should be surgically excised and
replaced with a prosthetic graft.
Inferior vena cava
ORIGIN
Forms from union of common iliac veins (L5)
COURSE
Ascends retroperitoneally, on R side of aorta.
R
TERM
BR
SS
CLINICAL
R ureter, R sympathetic trunk
Passes through caval foramen in central tendon of diaphragm (T8), drains into R atrium
Receives tributaries:
• Lumbar veins, median sacral vein, inf phrenic vein
• Renal vein, R gonadal & R suprarenal vein (L gonadal & suprarenal drain to L renal)
• Hepatic vein (splenic v, sup/inf mesenteric drain into portal circulation)
Drains blood fr lower limbs and abd viscera, except GIT.
• Trauma: IVC trauma is commonly lethal due to its inaccessibility and thin walls
• Pregnancy may compress the IVC, causing temporary ankle varicose veins
• Collateral circulation: superficial epigastric vein, thoracoepigastric vein (superficial),
via lumbar veins into the azygos venous system
NIGEL FONG 2011/2012
PAGE A201
M1 NOTES IN GROSS ANATOMY
Lymph nodes
6 | ABDOMEN
!
•
Pre-aortic lymph nodes: celiac, sup mesenteric, inf mesenteric nodes
•
- Drains GIT
Lateral aortic (para-aortic / lumbar) nodes, forming R/L lumbar trunks:
•
- Drain kidneys, suprarenals,
- Drain gonads, uterine tubes & fundus of uterus
- Drain deep lymph vessels of abdominal walls & common iliac nodes
Thoracic duct commences in abdomen as the cisterna chyli, inf to diaphragm on R
side of aorta.
NIGEL FONG 2011/2012
PAGE A202
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
CHAPTER 7: NORMAL STRUCTURE AND DEVELOPMENT OF THE
7 | PELVIS & PERINEUM
!
!
1. PELVIC WALLS, FLOOR & PERINEAL FASCIA
A. PELVIC GIRDLE
Pelvic bones
•
•
•
!
!
Innominate bone (ilium, ischium, pubis): also see lower limb
Sacrum: 5 fused sacral vertebrae
- Superior surface includes the ala (expanded wing-like transverse processes) and an
ant-projecting promontory
- Spinal nerves pass through the sacral canal, a continuation of the vertebral canal
- Ant/pos rami of spinal nerves emerge separately from ant/pos sacral foramina
Coccyx
Joints
TYPE
SUPPORT
MOVE
Lumbosacral [btw bodies]
[btw articular processes]
Intervertebral
Zygapophysial
IV disc
Iliolumbar, lumbosacral
Lim
Sacroiliac
Synovial
Ant, interosseous, pos ligaments
Interlocking surf resists mvmt
Sacrospinous, sacrotuberous lig resist rotn
Lim
Pubic symphysis
2º cartilaginous
Interpubic disc (fibrocartilaginous)
Sup & inf ligaments
Nil
Formation of the bony pelvis
•
Bony pelvis forms a strong basin-shaped structure
Transfers weight between axial skeleton to lower limbs for standing/walking
- Support the abdominal contents, contain and protect pelvic viscera
- Allow for passage of the fetus during childbirth
• In the anatomical position, symphysis pubis and ASIS line in the same vertical plane.
• Clinical: The pelvis is a brittle ring, fractures are usually multiple or in combination
with a joint dislocation; if a fracture is demonstrated on one side, suspect a second.
NIGEL FONG 2011/2012
PAGE A203
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
The pelvic cavity
•
The pelvis is inferioposterior to the abdomen
- Greater (false) pelvis sup to the pelvic inlet is functionally part of the abdomen
-
Lesser (true) pelvis is found between the pelvic inlet and outlet
•
Pelvic inlet is bounded by
•
- [pos] sacral promontory and ala of sacrum
- [lat]: iliopectineal line (arcuate / white line)
- [ant]: the symphysis pubis
Diamond-shaped pelvic outlet bounded by
-
[pos] coccyx, sacrotuberous ligaments
[lat] ischial tuberosities, ischiopubic rami
[ant] by pubic arch / symphysis
!
Pelvic inlet
Pelvic outlet
Differences in the male & female pelvis
MALE
FEMALE
FORM
A larger segment of a smaller cone:
Narrow and deep, tapering
A smaller segment of a larger cone:
Wide and shallow, cylindrical
INLET
Prominent projecting sacral promontory
Heart-shaped
No prominent projecting promontory
Oval-shaped
BONES
Ischial spine inverted
Sacrum & coccyx long, curve inwards
Ischial spine everted
Sacrum & coccyx short, straight
Soften during pregnancy due to hormones,
increasing potential size for childbirth
ANGLE
Angle formed by pubic arch narrow (<70º)
NIGEL FONG 2011/2012
Angle formed by pubic arch wide (>80º)
PAGE A204
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
Outlets from the pelvic girdle
•
•
•
•
•
•
The sacrotuberous (btw lat margin of sacrum & ischial tuberosity) & sacrospinous
(btw lat margin of sacrum & ischial spine, deep to sacrotub lig) ligaments convert the
greater and lesser sciatic notches into foramina.
The piriformis muscle further divides the greater sciatic foramen into two.
Passing through greater sciatic foramen:
- Sup to piriformis: sup gluteal n / vessels
- Inf to piriformis: inf gluteal n / vessels, sciatic n, pos femoral cut n, n to obturator
internus & quadratus femoris
Passing through lesser sciatic foramen: tendon of obturator internus
Passing through obturator canal: obturator n / vessels
Pudendal n & int pudendal vessels exit pelvis through greater sciatic foramen,
loop around the sacrospinous lig, and enter perineum through lesser sciatic foramen.
B. PELVIC FLOOR
!
NIGEL FONG 2011/2012
PAGE A205
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
!!!!!
!
Pelvic diaphragm
•
•
•
•
•
Division btw pelvis above & perineum below
Incomplete ant at the urogenital hiatus to allow passage of urethra and/or vagina
Tonically contracted and further contracts during activities that ↑ intra abdominal
pressure (micturition, defecation, childbirth, coughing, talking, sneezing, vomiting etc)
Closes the pos pelvic floor, supporting & preventing prolapse of pelvic viscera
Helps to maintain continence of bladder and rectum, however must relax during
micturition and defecation
!
!!!!!
!
!
Muscles of the pelvic diaphragm
•
•
Divided into component muscles but considered one morphological entity
Important sites of attachment:
- Perineal body: ant to anal canal, pos to urethra (M) / vagina (F)
- Anococcygeal body: btw anal canal & tip of coccyx
•
Puborectalis forms a sling pos to the anorectal junction, helping to maintain fecal
continence.
In addition, short muscular slips of the coccygeus form the pubovaginalis (F),
puboprostaticus, etc
•
!
MUSCLE
Levator ani:
[Ant] Puborectalis
[Mid] Pubococcygeus
[Pos] Iliococcygeus
(Ischio)coccygeus
NERVE
ORIGIN
Br fr S4
Br fr inf rectal /
perineal div of
pudendal n
Linear origin from
- Pelvic surf, body of pubis
- Obturator fascia (tendinous
arch / white line)
- Ischial spine
Br fr S4/S5
INSERTION
Sling ard anal c
Anococcygeal
body / coccyx
Coccyx
!
NIGEL FONG 2011/2012
PAGE A206
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
C. FASCIAL LAYERS OF THE PERINEUM
!
!
!
!
!
!
Boundaries of the perineum
•
•
Diamond shaped region inf to pelvic diaphragm, bounded by symphysis pubis, tip of
coccyx, and ischial tuberosities (all of which are palpable).
- To identify the pubic tubercle from the ant view: identify the ASIS from the iliac
crest and follow the inguinal ligament (visible on flexion of thigh) inferomedially
Perineum divided into two ∆ by an imaginary line joining the two ischial tuberosities
- Ant urogenital triangle [oriented in horizontal plane] – external genitalia
-
•
•
Pos anal triangle
[tilted, faces posteriorly]
– anus & ischioanal fossa
- Perineal body lies in the imaginary line
The urogenital diaphragm (perineal membrane, sup/deep pouches) covers the ant
urogenital triangle only
Examination of the perineal region is usually done in the lithotomy position: patient
supine, legs spread apart, and knees flexed
NIGEL FONG 2011/2012
PAGE A207
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
Urogenital triangle: Pouches
•
Deep perineal pouch: btw perineal membrane & inf fascia of pelvic diaphragm
•
- W membranous urethra, deep transverse perineal muscles, bulbourethral gland
Perineal membrane
•
- Tough fascia filling the gap (urogenital hiatus) in the pelvic diaphragm
- Final support for pelvic viscera
- Crura of penis attaches here
- Perforated by urethra and vagina
Sup perineal pouch: btw perineal membrane & perineal fascia
-
W Erectile bodies of ext genitalia and associated muscles, deep perineal branches of
int pudendal v / pudendal n
Urogenital triangle: external (perineal) fascia
•
•
•
Sup layer: Fatty, cont with ischioanal fat pad
Deep layer: Membraneous (Colles) fascia
- Pos: attached to perineal membrane, does not extend into anal triangle
- Lat: fuses with fascia lata, does not extend into thigh
- Ant: continuous with membranous layer of abdominal fascia and dartos fascia of
penis/scrotum
Clinical: Implications for extravasation of urine upon rupture of urethra (see urethra)
NIGEL FONG 2011/2012
PAGE A208
M1 NOTES IN GROSS ANATOMY
!
7 | PELVIS & PERINEUM
Anal triangle: Ischioanal (ischiorectal) fossa
•
•
•
•
•
Wedge-shaped spaces bounded inf by the external skin, med/sup by levator ani, and lat
by obturator internus muscles
L/R ischioanal fossa communicate between the anal canal & tip of coccyx
Ischioanal fossa are filled with fat, which is readily displaced to permit expansion of the
anal canal during passage of feces
The pudendal canal, in which the pudendal nerve & int pudendal vessels travel, lie
on the lateral wall of the ischioanal fossa
Clinical: perianal abscesses may form due
to tear in anal mucus membrane (allowing
fecal bacteria infection) or external wound
- More painful in the lobulated fat of the
perianal space (inferior) as septa
between fat prevents expansion and
causes tension
!
!
NIGEL FONG 2011/2012
!
PAGE A209
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
2. PELVIC & PERINEAL VISCERA
!
A. PERITONEUM
!
Overview
•
•
•
Pelvic viscera includes distal part of urinary system (bladder, urethra), GIT (rectum,
anus), and reproductive system.
Pelvic viscera are retroperitneal, covered by peritoneum only on sup surf
- Except ovaries, uterine tubes: intraperitoneal (uterine tubes also w mesentery)
Note relations btw vagina, bladder, rectum: fistulae may form btw adj openings
Male peritoneal reflections
•
•
•
Passes down ant abd wall onto upper surf of urinary bladder (laterally, peritoneum
passes to lat pelvic walls and does not cover lat surf of bladder)
- As bladder fills, sup wall rises up into abdomen and peels off peritoneum fr ant abd
wall (here, peritoneum not firmly bound to underlying structures)
- Clinical Suprapubic cystotomy: Distended bladder may be punctured or
approached surgically sup to pubic symphysis, without entering the peritoneal
cavity. This is useful for catheterization, removing foreign bodies, tumours etc.
Forms rectovesical pouch by dipping behind pos surf of bladder for short distance,
to upper end of seminal vesicles
- Dependent position (lowest in erect position), fluid may accumulate here
- Also forms in females who have had a hysterectomy (removal of uterus)
Passes up rectum
- Distal 1/3 of rectum: not covered by peritoneum
- Middle 1/3 of rectum: covered by peritoneum on ant surf
- Prox 1/3 of rectum:
covered by peritoneum on ant & lat surf
NIGEL FONG 2011/2012
PAGE A210
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
Female peritoneal reflections
•
•
Passes down ant abd wall onto upper surf of urinary bladder
Reflects onto ant surf of uterus at the isthmus (does not reach ant vaginal fornix),
forming the vesico-uterine pouch
•
•
Passes upward over ant surf of body & fundus of uterus, and downward over pos surf,
covering the pos vaginal fornix
Forms the rectouterine pouch (pouch of Douglas)
•
- Dependent part of abdominopelvic peritoneal cavity, fluid may accumulate
- Palpable from the pos vaginal fornix, via per-vaginal examination
Passes ant to rectum as in the male
Formation of the broad ligament
•
•
•
•
•
Double-layer peritoneal fold btw uterus and lateral pelvic wall on each side
Lat continuation of peritoneum as it passes up and over the uterus (hence 2 layers: 1
layer fr peritoneum on ant surf of uterus, 1 layer fr peritoneum on pos surf)
Sup, both layers are continuous and form the upper free edge
Inf, at base of ligament, layers separate to cover pelvic floor
See female reproductive viscera
!
NIGEL FONG 2011/2012
!!
PAGE A211
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
B. GIT VISCERA
!
!
Rectum & Anus
LOC
Continuation of sigmoid colon (at S3), follows concavity of sacrum
Rectum ends and anus begins anteroinferior to tip of coccyx
ANT
STR
M:
Pos surf bladder (w vas deferens, seminal vesicles), prostate, membraneous
urethra, rectovesical pouch, perineal body
F:
Pouch of douglas, pos surf vagina, perineal body
POS
Sacrum, coccyx, anococcygeal body, coccygeus, piriformis, sacral plexus,
sympathetic trunks
LAT
Ischiorectal fossae
Rectum forms an S-shape (lat view), following the concavity of sacrum, before a sharp
anorectal flexure (maintained by the puborectalis)
• Teniae coli come together to form a broad band, with no appendices epiploicae
• Transverse rectal folds (lat flexures), varying in pos, help to maintain fecal continence
Pectinate line divides upper half and lower half of the anal canal
• Upper half with anal columns, joined together at lower ends into anal valves
• Lower half without anal columns
FUNC
Store feces
Distal opening of the GIT
!
NIGEL FONG 2011/2012
PAGE A212
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
!
SUP TO PECTINATE LINE
develops fr hindgut
BLOOD
INF TO PECTINATE LINE
develops fr ectoderm
Portal system:
Caval system
Caval system
ART
fr/to inf mesenteric
Sup rectal art (1x)
fr/to int iliac
Middle rectal art (2x)
fr/to int pudendal
Inf rectal art (2x)
VEN
Sup rectal vein (1x)
Middle rectal v (2x)
Inf rectal vein (2x)
Int & ext v plexuses (porto-systemic anastomoses) normally appear varicose
NERVE
CLIN
!
LYM
To pararectal & inf
mesenteric nodes
To int iliac nodes
PAR
Autonomic: inf hypogastric
plexus & pelvic splanchnic n
Somatic: inf rectal nerve (S4)
Sensitive only to stretch
Sensitive to pain, touch, temperature, pressure
To sup inguinal nodes
• Internal hemorrhoids (piles): musoca prolapses w the normally dilated internal
rectal plexus. Tendency to strangulate, ulcerate, and bleed.
• External hemorrhoids: thromboses in external rectal venous plexus
• Prolapse may result from levator ani tears (e.g. childbirth), poor tone, or starvation
(usage of fats in the ischioanal fossa)
• Per-rectal examination allows for examination of rectum & related strs
!
Anal sphincters:
•
•
Helps to maintain fecal continence by tonic contraction
Internal anal sphincter: smooth muscle under autonomic involuntary control
•
- Forms fr circular layer of muscularis mucosa
- Tonically contracted by sympathetic stimulation, inhibited by parasympathetic
External anal sphincter: skeletal muscle under somatic voluntary control
-
•
Divided into subcutaneous, superficial, and deep parts.
Only the superficial part is attached pos to the coccyx and ant to perineal body,
the other 2 parts do not have bony attachments
Puborectalis also helps to maintain fecal continence
NIGEL FONG 2011/2012
PAGE A213
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
C. URINARY VISCERA
Bladder
LOC
Immediately behind pubic bones within the pelvis
When full, sup wall rises up into the hypogastric region
MALE
ANT
Symphysis pubis, ant abd wall when full
POS
Vas deferens, seminal vesicles,
rectovescial pouch
Vagina
SUP
Peritoneum, Ileum / sigmoid colon
Peritoneum, uterus, uterovesical pouch
LAT
INF
STR
FEMALE
Pubic bones, obturator internus, levator ani
Prostate
Urogenital diaphragm
Pyramidal in shape
• Apex points ant, connected to umbilicus by median umbilical lig (remnant of urachus)
• Base faces pos and is triangular (corners: 2 ureter openings & urethral orifice)
• Internal surface of the base forms the trigone (smooth, no crenations)
• Neck of bladder lies inf, held in pos by puboprostatic (M) /pubovesical (F) ligaments
Bladder walls
• formed by smooth Detrusor muscle
• At the neck, the detrusor muscle forms the internal urethral sphincter
• Ureters pierce the bladder wall obliquely, giving a valvelike mechanism to prevent
reverse flow of urine towards the kidneys as the bladder fills
FUNC
BLOOD
NERVE
Stores urine, with max capacity of 500mL
ART
Sup & inf vesical arteries, fr int iliac art
VEN
Vesical venous plexus, drains into int iliac vein
LYM
To int & ext iliac nodes
From inf hypogastric plexus
• Sym: fr L1/L2, via plexus
• Parasym: fr pelvic splanchnic n (S2-S4).
CLIN
See suprapubic puncture & kidney stones, see embryology
In rupture, whether urine extravasatesinto extraperitoneal vs intraperitoneal spaces
depends on which part of bladder ruptures (see relationship to peritoneum)
NIGEL FONG 2011/2012
PAGE A214
M1 NOTES IN GROSS ANATOMY
Persistent urachus
7 | PELVIS & PERINEUM
REG
Bladder
MODE
Ascending urethrogram: Xray w contrast inj upwards
COND
Persistent urachus
VIS
Contrast ascends up ant
abdominal wall and spills out
through umbilical reg.
NOTE
!
Nervous control of micturition
•
Micturition reflex (involuntary)
- Stretch receptors in the bladder wall send sensory signals through the
parasympathetic pelvic nerves, resulting in desire to void
- Signals are sent back to the bladder via the same parasympathetic pelvic
nerves, triggering detrusor muscle contraction and internal sphincter relaxation.
•
However the external urethral sphincter is under somatic motor (voluntary) control,
allowing us to choose when to void
Autonomic dysfunction in spinal cord injuries
•
Automatic reflex / hypertonic / hyperreflexive bladder
•
- Spinal cord injury above S2
- Bladder fills and empties reflexly and micturition cannot be voluntarily controlled
- Also seen in babies
Autonomous / flaccid / hypotonic / hyporeflexive bladder
-
Spinal cord injury at sacral segment
No reflex control, bladder is flaccid
Bladder fills to capacity and overflows a few drops at a time.
May be partially emptied by manual compression of lower part of ant abd wall
Complication: chronic urinary tract infection, kidney failure due to back pressure
NIGEL FONG 2011/2012
PAGE A215
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
Female urethra
•
•
•
Short (4cm)
Fr neck of bladder to external meatus, opening into vestibule ant to vaginal opening
- Ext urethral sphincter forms as urethra passes through the UG diaphragm
- Paraurethral glands (Skene’s glands, correspond to prostate) open into sides
Clinical: the female urethra is shorter and more prone to urinary tract infection
!
Male urethra
•
•
!
Long (20 cm), S-shaped with 2 bends [J-shape when erect / lifted up]
Prostatic urethra: fr neck of bladder to apex of prostate
-
•
Wide & most dilatable part of urethra
Marked by urethral crest (longitudinal mucosal fold), with prostatic sinuses on
either side, into which prostatic ducts empty
Membranous (intemediate) urethra passing through the UG diaphragm
•
- Short, least dilatable
- Surrounded by ext urethral sphincter (skeletal muscle)
Penile (spongy) urethra: within corpus spongiosum of penis
-
Ext meatus, a sagittal slit, is narrowest part of urethra
Enlarged to form a bulb at the base of the penis and in glans penis to form the
navicular fossa
1st bend as urethra exits deep perineal pouch and turns anteriorly in body of penis
2nd bend when passing from root to body of penis; this bend disappears in erection
!
NIGEL FONG 2011/2012
PAGE A216
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
Rupture of male urethra
•
•
•
•
Can occur due to iatrogenic injury (cateterization injury, usually at the 1st bend) or
trauma, causing extravasation of urine
Pelvic fractures usually rupture membranous urethra, straddle injuries commonly
involve bulbous urethra.
Rupture of membranous urethra (most common) results in extravasation of urine into
deep perineal pouch and extraperitoneally around prostate & bladder
Rupture of spongy urethra results in extravasation of urine into the superficial perineal
space: loose connective tissue in the scrotum, penis, up to the ant abdominal wall
- Not into the thigh because the perineal fascia fuses with the fascia lata
- Not into anal triangle because perineal fascia fuses with pos layer of perineal
membrane
REG
Bladder, urethra, penis
MODE
Ascending urethrogram: Xray w contrast inj upwards
COND
Urethral rupture
VIS
Contrast spilling out of the
urethra.
NOTE
NIGEL FONG 2011/2012
PAGE A217
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
D. MALE REPRODUCTIVE SYSTEM
!
Testes & Epididymis
TESTES
EPID
Testes : 5 x 2.5 x 2.5 cm
• Tunica albuginea: Tough fibrous capsule,
thickened posteriorly at mediastinum testes
• Anchored posteriorly
• Seminiferous tubules lie within lobules, opening
into a network of channels, the rete testes
• Efferent ductules connect the rete testes to the
epididymis
Epididymis (pos to scrotum)
• Coiled tube 6m long, forming head, body, tail
• Vas deferens emerges from tail
FUNC
BLOOD
NERVE
CLIN
Testes: spermatogenesis
Vas deferens: storage, maturation, and nourishment
ART
Testicular artery, from abdominal aorta just inf to renal artery, crossing over
ureters and passing through inguinal canal
VEN
Pampiniform plexus, forming testicular vein
R: Joins IVC | L: Joins L renal vein
LYM
To lumbar (caval/aortic) and preaortic nodes
Vagal parasympathetic & sympathetic fibres
• Undescended testes may be found anywhere along route of descent (up to level of
kidneys) or ectopic (prepenile, femoral, perineal etc). Undescended testes have a higher
risk of carcinoma.
• Hydrocele: a usually idiopathic accum of excess fluid in persistent processus vaginalis.
Transillumination (applying bright light to side) results in a red glow, indicating light
passing through excess serous fluid
• Hematocele: blood does not transilluminate
• Torsion of spermatic cord (twisting): happens with loss of posterior anchoring of
testes (tunica vaginalis completely surrounds testes), results in obstruction of arterial
supply & venous drainage, possibly resulting in edema, hemorrhage, and necrosis
• Cancer: note that cancer of the testes metastasize to the lumbar lymph nodes while
cancer of the scrotum metastasize to sup inguinal nodes
NIGEL FONG 2011/2012
PAGE A218
M1 NOTES IN GROSS ANATOMY
Ultrasound of testes
7 | PELVIS & PERINEUM
REG
Testes
MODE
Ultrasound
COND
Normal
VIS
Note tunica albuginea &
tunica vaginalis
NOTE
!
REG
Testes
MODE
Ultrasound + doppler
COND
Testicular torsion with
infarction
VIS
Red spots: blood supply
NOTE
Surgical emergency
REG
Testes
MODE
Ultrasound
COND
Testicular rupture
VIS
Incomplete tunica albuginea
LHS: testicular material spill
out of testes
!
NOTE
!
Vas deferens (ductus deferens)
•
•
•
•
•
•
Begins in tail of epididymis
Ascend pos to testis, medial to epididymis
Passes (as part of the spermatic cord) through the inguinal canal into the ant abd wall
Pass downwards & backwards on the lat wall of pelvis, on ext surf of peritoneum
- Directly contacts peritoneum, no other str btw peritoneum & vas deferens
- Cross ant/sup to ureter
Near the neck of bladder, vas deferens joins duct of seminal gland to form ejaculatory
duct which passes through posterior part of prostate
Clinical: Vasectomy involves ligation of vas deferens (through incision in sup part of
scrotum) to result in in male sterilization
!
Seminal gland (vesicle)
•
•
•
Elongated str, lie btw fundus of bladder & rectum, pos to ureters, sup to prostate
Duct joins ductus deferens to form ejaculatory duct
Secretes alkaline seminal fluid w fructose, vitamin C, prostaglandin, coagulating agent
NIGEL FONG 2011/2012
PAGE A219
M1 NOTES IN GROSS ANATOMY
!
Prostate
LOC
STR
FUNC
BLOOD
NERVE
CLIN
7 | PELVIS & PERINEUM
Surrounds prostatic urethra
SUP
Neck of bladder
INF
Urogenital diaphragm, ext urethral sphincter
ANT
Symphysis pubis (separated by extraperitoneal fat), puboprostatic ligaments
POS
Rectum (separated by rectovesical septum)
LAT
Levator ani muscle
Largest male reproductive accessory gland: 3cm long, chestnut size
• Base rests against bladder neck, Apex lies against urogenital diaphragm
• Outer fibrous capsule, inner smooth muscle & connective tissue
• Ejaculatory ducts pierce the pos surface of prostate to open into prostatic urethra
• Divided into lobes: ant, median, pos, R/L
• Numerous glands opening into prostatic urethra.
Prod thin milky alkaline fluid w citric acid, acid phosphatase (neutralize vaginal acidity)
Smooth muscle squeezes secretion into prostatic urethra during ejaculation
VEN
Inf vesical & middle rectal art
Prostatic venous plexus (receiving deep dorsal vein of penis)
Drains into int iliac veins
LYM
To int iliac nodes
ART
From inf hypogastric plexus
• Can be examined by per-rectal examination
• Most accessible for ultrasound or biopsy through per-rectal route
• Benign prostatic enlargement common in men older than 50 yrs, aggravated by
wine, cold weather, and women. May lead to nocturia (need to void at night), dysuria
(difficulty/pain during urination), and urgency
• Prostatic venous plexus has rich communication w vertebral veins, prostate cancer may
result in metastasis to the vertebrae and brain
NIGEL FONG 2011/2012
PAGE A220
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
!
Penis
ROOT
!
!
Bulb of penis
• Loc in midline, attached to undersurface of urogenital diaphragm
• Transversed by urethra
• Continues into body of penis as the corpus spongiosum
Crura of penis
• Located on either side, attached to pubic arch
• Converge ant & form corpora cavernosa
BODY
Body: free pendulous part suspended from the pubic symphysis. Base supported by
• Suspensory ligament of penis (attached to pubic symphysis)
• Fundiform ligament of penis (attached to linea alba of ant abd wall)
Consists of 2 dorsal corpora cavernosa & 1 ventral corpus spongiosum (note: normal
anatomical position of the penis is erect)
• At distal extremity, corpus spongiosum expands to form the glans penis
• Urethra travels in corpus spongiosum, opening into the ext urethral meatus
• Prepuce (foreskin) covers the glans (the frenulum is a fold of skin passing from deep
layer of prepuce to urethral surface of glans)
FUNC
BLOOD
NERVE
CLIN
Copulation: in erection, blood sinusoids of corpora cavernosa & corpus spongiosum bec
engorged with blood
Common outlet for urine and semen
ART
Branches of int pudendal arteries:
• Dorsal art of penis: in dorsal groove btw corpora cavernosa
• Deep art of penis: near ctr of corpora cavernosa [coiled when penis flaccid]
• Arteries of bulb of penis
VEN
Dorsal vein of penis (1), coursing btw 2 dorsal arteries
Passes through gap btw pubic symphysis & deep perineal pouch to drain into
prostatic venous plexus
LYM
Sup inguinal nodes / int iliac nodes
Dorsal nerve of penis
Circumcision is the surgical removal of the prepuce, either for religious tradition or to
remove recurrent irritation by smegma (oily secretions) in the preputial sac
NIGEL FONG 2011/2012
PAGE A221
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
Erection & Ejaculation
•
•
Combination of neural and psychic stimuli
Erection is mediated by parasympathetic stimuli
-
•
Preganglionic neurons fr pelvic splanchnic n (S2-S4), via inf hypogastric plexus,
synapsing on pelvic plexus
- Smooth arterial muscle relax while venous return impeded, allowing blood to flow
into and dilate copora of penis (further impeding venous return), causing erection
Ejaculation is mediated by sympathetic stimuli
-
•
Via hypogastric plexus, sympathetic ganglia
Semen delivered to prostatic urethra via peristalsis of vas deferens, prostatic fluid
added by contraction of smooth muscle in prostate
Erectile tissue in clitoris of female is similarly innervated.
Superficial perineal muscles of male
•
•
•
•
Located in the superficial perineal pouch
Sup transverse perineal muscles and bulbospongiosus attach to the perineal body,
supporting the pelvic viscera
Bulbospongiosus compresses the bulb of the penis & corpus spongiosum, aiding in
emptying the spongy urethra of residual urine / semen. The reflex contraction during
ejaculation is responsible for the pulsatile emission of semen from the penis
Ischiocavernosus muscles surround crura in root of penis, forcing blood into corpora
cavernosa, assisting in erection.
!
E. FEMALE REPRODUCTIVE SYSTEM
!
The Vulva (female UG triangle)
•
•
•
•
Mons pubis: hair-bearing elevation of
skin ant to pubis
Labia majora: protective folds of skin
Labia minora: smaller folds of skin btw
the labia majora
- Unite pos to clitoris, forming frenulum
- Unite ant to clitoris, forming prepuce
Vestibule of vagina inside labium minora
-
Ant ext urethral orifice
Pos vaginal orifice
NIGEL FONG 2011/2012
!
PAGE A222
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
Clitoris
•
•
Erectile organ for sexual arousal, highly sensitive and richly innervated (same as penis)
Body of clitoris consist of the two corpora cavernosa,
•
- Ant cont. of the crura which are attached to either side of the urogenital triangle
Bulbs of vestibule situated on either side of vaginal opening
•
•
- Attached to the clitoris but do not form part of its body (unlike in the male)
Perineal muscles in the female correspond to the male, but are less well developed in
the absence of functional demands related to urination, ejaculation, etc
Clinical: Female circumcision practiced in some cultures removes the prepuce of the
clitoris, or the clitoris entirely. It is disfiguring and discouraged.
!
Vagina
LOC
STR
FUNC
BLOOD
Ext upward & backward btw vulva & uterus (through perineum and pelvis)
ANT
Bladder, urethra
POS
Pouch of douglas, ampulla of rectum, perineal body
LAT
Ureter, Levator ani, urogenital diaphragm, bulb of vestibule
Muscular tube
Vaginal orifice is covered in virgins by the hymen, which tears aft first coitus
Female sexual organ, excretory duct for menstrual flow, and birth canal
Vaginal artery, fr int iliac
Vaginal branch of uterine art
VEN
Plexus drains into int iliac
ART
LYM
NERVE
CLIN
To ext/int iliac nodes (pelvic part) and sup inguinal nodes (perineal part)
From inf hypogastric plexus
• Per-vaginal examination allows examination of the vagina, cervix, and related str.
Alteratively use a speculum. Vagina should be pinkish, check for ulcers or cancer.
Blood indicates menses, abortion, etc
• Culdocentesis: passage of needle through pos fornix into the pouch of douglas allows
drainage of pelvic abscess
• Pap smear involves insertion of spatula & cytobrush through vagina to collect
cellular material from cervical mucosa
• Episiotomy: vaginal delivery may result in traumatic tearing of the perineum, esp
when descent of the fetus is arrested or when instrumentation (e.g. obstetrical forceps)
is used. In such cases, an surgical incision to enlarge the vaginal orifice (i.e.
episiotomy) is performed to decrease traumatic tearing. The incision is usually
posterolateral, avoiding the perineal body and directing further tears away from anus.
NIGEL FONG 2011/2012
PAGE A223
M1 NOTES IN GROSS ANATOMY
Uterus
LOC
STR
7 | PELVIS & PERINEUM
!
Lies in lesser pelvis, with body lying on urinary bladder, cervix btw bladder & rectum
ANT
Uterovesical pouch, sup surf of bladder
POS
Pouch of douglas (may include ileum / sigmoid colon), rectum
LAT
Broad ligament, uterine art/vein, uterine tubes entering
INF
Vagina
Hollow, pear shaped, thick muscular walls.
• Fundus lies above entrance of uterine tubes (which enter at superolateral angles)
• Body lies below entrance of uterine tubes (when collapsed, cavity of uterine body is
merely a cleft in the sagittal plane)
• Cervix pierces ant wall of vagina, communicating with the body through the internal
os and with the vagina through the external os.
Uterus lies on almost horizontal plane
• Anteversion: long axis of uterus bent forward on long axis of vagina
• Anteflexion: long axis of body of uterus bent forward on long axis of cervix
FUNC
BLOOD
Reception, retention, nourishment of fertilized ovum
ART
VEN
LYM
NERVE
CLIN
Uterine art, fr int iliac art.
• Runs med in base of broad lig to reach uterus, crossing ant & 90º to urethra
• Reaches cervix at level of internal os, asc along lat margin of uterus within
broad ligament, anastomoses w ovarian art
Uterine vein, to int iliac vein
From fundus: accompany ovarian artery to para-aortic nodes at L1
Body and cervix: to int/ext iliac nodes
From inf hypogastric plexus
However uterine muscular activity is independent of extrinsic innervation, spinal
anesthesia does not interfere with labour contractions
• Through per-vaginal exam, cervix feels firm if non-pregnant, but softer if pregnant
• Uterus is a dynamic structure, growing during puberty, expanding into the abdomen
during pregnancy, and decreasing in size after menopause
• Hysterectomy (excision of uterus) can be done via ant abd wall or vaginal approach
NIGEL FONG 2011/2012
PAGE A224
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
Support of the uterus
•
•
At level of vagina - Levator ani muscles, perineal body, urogenital diaphragm
At level of cervix – subperitoneal condensations of pelvic fascia on sup surf of lev ani
- Transverse cervical (Cardinal) lig: to lat wall of pelvis
-
•
•
•
Pubocervical lig: to pos surf of pubis
Sacrocervical lig: to sacrum
Round ligament fr superolat angle of uterus, through inguinal canal to subcut tissue
of labium maj: helps to keep uterus anteverted and antiflexed
Body of uterus rests on the bladder
Clinical: Prolapse of the uterus & vagina (or back pain) can result due to damage to
these supporting structures
!
Contents of broad ligament
•
•
•
Formation of broad ligament: see female peritoneal reflections
Uterine tube in upper free border
Vestiges of the ovarian gubernaculum attaching to the uterotubal junction:
- Round ligament of uterus lies ant/inf (going to inguinal canal)
-
•
•
Ligament of ovary lies pos/sup, both
Support of the ovary within the broad ligament
- (round) Ligament of ovary attaches the ovary to the uterus,
- Suspensory ligament of ovary (containing the ovarian vessels) attaches the
ovary laterally to the pelvic wall
Uterine & ovarian blood vessels, lymph vessels, nerves
!
Ovaries
LOC
Suspended intraperitoneally within mesovarium (subdivision of broad ligament), btw the
suspensory ligament of ovary & ligament of ovary.
Extremely variable position
STR
Oval shaped, 4cm x 2cm
Surrounded by tunica albuginea (fibrous capsule), scarred due to ovulation aft puberty
Oogenesis
ART
Ovarian artery: from abdominal aorta at L1 level
VEN
Ovarian vein: to IVC on RHS and L renal v on LHS
LYM
Follow ovarian artery, draining into para-aortic nodes at L1
FUNC
BLOOD
NERVE
Fr aortic plexus, accompanying ovarian artery
NIGEL FONG 2011/2012
PAGE A225
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
Uterine tubes
LOC
Upper free edge of broad ligament, connecting peritoneal cavity in the region of the ovary
with cavity of uterus
STR
10cm long, divided into [lat-med]
• Infundibulum – funnel-shaped lat end, with finger-like fimbriae adj to pole of ovary
• Ampulla – widest part of tube in which fertilization usually occurs
• Isthmus – narrowest part, just lat to uterus
• Intramural part – pierces uterine wall
Receives the ovum from the ovary, nourishes and transports it to the uterus
Location for fertilization, conduit for sperm
ART
Uterine vessels, fr int iliac art
Ovarian vessels, fr abdominal aorta
VEN
Correspond to art
LYM
Int iliac / paraaortic nodes
FUNC
BLOOD
NERVE
CLIN
!
!
!
Fr inf hypogastric plexus
• Female genital tract communicates with peritoneal cavity through open end of uterine
tubes, so infections of the vagina, uterus, and tubes may result in peritonitis while
inflammation of a tube (salpingitis) may result from peritoneal infections
• Ligation of uterine tubes is a method of birth control.
• Ectopic tubal pregnancy – see embryology
Imaging of the female genital tract
!
!
NIGEL FONG 2011/2012
REG
Ovaries & Uterus
MODE
Ultrasound
COND
Normal
VIS
Ovarian follicles appear like
raisins
Thickness of uterine lining
differs with menstrual cycle
& menopause: thickest just
before menstruation
NOTE
Knowing normal thickness
impt for diagnosis of
endometrial CA
!
PAGE A226
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
REG
Female genital tract
MODE
MRI
COND
Normal
VIS
Look out for normal
separation of bladder, vagina,
and rectum by fat. In CA
patient, this indicates that
CA has not spread.
NOTE
!
REG
Female genital tract
MODE
Hysterosalpingogram:
contrast injection into cervix
COND
Normal
VIS
Contrast spills out of both
fimbrial ends, which open
into the peritoneal cavity
NOTE
Study commonly done to
check for uterine tube
blockage in pt with fertility
problems (contrast will not
spill out on one end)
REG
Female genital tract
MODE
Hysterosalpingogram:
contrast injection into cervix
COND
Normal, study complicated
by venous intravasation
VIS
Study done during
menstruation: vessels
engorged, so contrast extends
into veins, draining into int
iliac veins.
NOTE
Try not to do
hysterosalpingogram during
menstruation
!
NIGEL FONG 2011/2012
PAGE A227
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
3. NEUROVASCULATURE IN THE PELVIS & PERINEUM
!
A. NERVES OF THE PELVIS & PERINEUM
!
!
Sacral plexus
•
•
•
On pos pelvic wall, ant to
piriformis
Formed fr ant rami L4-S4
Most branches leave from
greater sciatic foramen to
supply lower limb
(see lower limb)
!
!
!
!
NIGEL FONG 2011/2012
!
PAGE A228
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
Autonomic supply
•
•
•
•
•
•
The abdominal sympathetic trunk continues in the pelvis, running ant to sacrum,
converging & uniting in front of the coccyx as the ganglion impar
Pelvic splanchnic nerves (parasympathetic) arise from S2-S4 to join inf hypogastric
or sup hypogastric / inf mesenteric plexus
Sup hypogastric plexus (mixed): forms as a continuation of the aortic plexus, ant to
promontory of sacrum
Inferiorly, sup hypogastric plexus divides to form R/ L hypogastric nerves, which
then form the inf hypogastric plexus
Inf hypogastric plexus (mixed): Lies on either side of rectum, base of bladder, and
vagina.
These autonomic fibres are distributed to pelvic viscera.
Visceral afferents
•
•
Visceral reflex travels with parasympathetic fibres (i.e. pelvic splanchnic, S2-S4)
Visceral pain sensation depends on loc of str relative to pelvic pain line (middle of
sigmoid colon, or inf limit of peritoneum for all other str)
- Sup to pelvic pain line, follow sympathetics to inf thoracic / upper lumbar ganglia
- Inf to pelvic pain line, follow parasympathetic fibres to pelvic splanchnic n
Dermatomes
• Ant part of perineum supplied by ilio-inguinal nerve, pos part by pudendal nerve
!!!!!!!!!!!
NIGEL FONG 2011/2012
PAGE A229
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
!
!
Pudendal nerve (/artery)
ORIGIN
COURSE
REL
BR
SS
CLIN
!
N: sacral plexus (S2-S4) / A: int iliac artery
Leaves pelvis through greater sciatic foramen inf to piriformis.
Hooks around ischial spine & sacrospinous lig, enters perineum thru lesser sciatic foramen
Runs forward in the pudendal canal (lat wall of ischioanal fossa)
Accompanied throughout its course by the int pudendal vessels (nerve med, art lateral)
Inf rectal n: travel med Perineal n: passes into Dorsal n of penis/clitoris
across ischioanal fossa
UG triangle
Along lat margin of deep perineal
pouch, dorsal surf of clitoris/penis
Ext anal sphinc, lev ani
Muscles of UG triangle
Skin of anal triangle
Skin on pos surf of Sensory to penis/clitoris
scrotum/labia maj
Pudendal nerve block anesthesia
• Males: through perineal skin, lat to sacrospinous lig, near attachment to ischial spine
• Females: inject through vagina
!
!
NIGEL FONG 2011/2012
PAGE A230
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
B. ARTERIAL SUPPLY OF THE PELVIS & PERINEUM
Division of the common iliac arteries
•
•
Ant to sacroiliac joint, common iliac arteries divide into ext/int iliac arteries
Ext iliac artery runs along medial border of psoas, following pelvic brim
- Gives off inf epigastric artery & deep cricumflex iliac branches
- Leaves false pelvis by passing under inguinal lig to become femoral art
!
Int iliac artery
ORIGIN
COURSE
From division of common iliac artery
Passes down into pelvis
At upper margin, divides into ant / pos divisions
ANT DIV
Supplies pelvic viscera, perineum, gluteal region, adductor region of thigh
• Umbilical art: to umbilicus, large in fetus, becomes med umbilical lig in adult
• Sup vesical artery: to bladder (usu arises fr umbilical art)
• Inf vesical art (M) / Vaginal art (F): to bladder, prostate, vas deferens / vagina
• Middle rectal art: to rectum (sometimes arises from inf vesical art)
• Obturator art: to lower limb via obturator canal (with obturator n & vein)
• Int pudendal art: main art of perineum. Branches & supply sim to pudendal nerve
• Inf gluteal art: leaves pelvis through greater sciatic foramen inf to piriformis
• Uterine art: along lat fornix of vagina, lat margin of uterus, anastomose w ovarian a
POS DIV
Supplies lower pos abd wall, pos pelvic wall, gluteal region.
• Iliolumbar art: asc lat back out of pelvic inlet, div into iliac & lumbar br, ss muscle
• Lat sacral art: along pos pelvic wall, to bones, vertebral canal, sacral area
• Sup gluteal art: leaves pelvis through greater sciatic foramen sup to piriformis
CLIN
Int iliac artery has rich collateral circulation which can take its place if the int iliac artery
is ligated
NIGEL FONG 2011/2012
PAGE A231
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
Structures crossing the ureter
•
•
•
F: Uterine art crosses ant/sup to ureter lat to cervix (“water under the bridge”)
M: Ductus deferens crosses over the ureter pos to bladder
Important relationship during surgery e.g. hysterectomy
!
!
C. DRAINAGE OF THE PELVIS & PERINEUM
Venous drainage
•
•
•
•
•
•
Generally follow the arteries (exceptions below): perineal veins form the internal
pudendal vein, which joins the int iliac vein
Extensive prostatic / vesical (pelvic) venous plexus associated with inf surface of
pelvic floor viscera
Deep dorsal vein of penis/clitoris passes through gap btw pubic symphysis (/ inf
pubic lig) & deep perineal pouch, joining the prostatic venous plexus
Ovarian veins follow the arteries to the L renal vein / IVC in the abdomen
Superficial veins fr skin of penis/clitoris drain into the ext pudendal vein, which is a
tributory of the great saphenous vein
Superior rectal veins are part of the portal sys, draining into the inf mesenteric veins
NIGEL FONG 2011/2012
PAGE A232
M1 NOTES IN GROSS ANATOMY
!
7 | PELVIS & PERINEUM
!
Lymphatic drainage
•
•
•
Ext iliac nodes:
Int iliac nodes:
Superficial inguinal nodes:
•
Lateral aortic / lumbar nodes:
•
Inf mesenteric nodes:
NIGEL FONG 2011/2012
-
Sup parts of bladder / cervix
Most pelvic viscera, deep regions of perineum
Skin of perineum
Sup tissues of penis, scrotum, clitoris, labium maj
Anal canal inf to pectinate line
Testes, urethra, epididymis
Ovaries, Fundus of uterus, lat uterine tube
Superiormost rectum, sigmoid colon
PAGE A233
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
4. DEVELOPMENT OF THE REPRODUCTIVE SYSTEM
!
A. GONADS
Indifferent gonads
•
•
•
•
!
Urogenital ridge develops from intermediate mesoderm along pos wall of abd cavity;
this then gives rise to a genital/gonadal ridge.
Primordial germ cells invade genital ridge to induce gonad development (week 6)
- Migrate fr original loc among endoderm cells in wall of yolk sac close to allantois
- Gonads do not develop if germ cells absent
Epithelium penetrate mesenchyme to form primitive sex chords (remain connected to
surface epithelium)
Indifferent gonads similar in both sexes
Testis
•
Week 7: SRY gene of Y chromosome induce development of testes
•
Primitive sex cords continue to proliferate and penetrate deep into medulla to form
horseshoe-shaped testis (medullary) cords
-
•
•
!
Contain primitive germ cells and Sertoli cells (from
gland epithelium)
- At hilum: break up into network of tiny strands
which form rete testis
Leydig cells lie btw testis cords
- Diff. fr mesenchyme of gonadal ridge to induce
differentiation of genital ducts & ext genitalia
- Prod testosterone by 8th week
!
Mature at puberty: testis cords remain solid until puberty, when they acquire a lumen
to form seminiferous tubules
Ovary
•
•
•
Without SRY, primitive sex cords dissociate into irreg
cell clusters, then disappear
- Primitive germ cells left in medulla: form oogonia
Surf epithelium proliferates, forms cortical cords (2nd
generation of cords) which penetrate the mesenchyme
Cortical cords split into isolated cell clusters surr
primitive germ cells: form follicular cells
!
NIGEL FONG 2011/2012
!
PAGE A234
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
Descent of gonads
•
•
•
Testes descend into scrotum: see abdomen (inguinal)
Ovaries descend much less than testes, settling just below rim of true pelvis
Genital ligaments (remnants of urogenital mesentry aft mesonephros degradation)
- Cranial part form suspensory lig of ovary
- Caudal part forms ligament of ovary proper and round ligament of uterus
B. GENITAL DUCTS
!
Indifferent stage
•
•
•
Initially, both males and females have two sets of genital ducts
Mesonephric (Wolffian) ducts: see mesonephros
Paramesonephric (Mullerian) duct: invagination of epithelium on ant/lat surf of
urogenital ridge
Male genital ducts
•
As mesonephros regresses, mesonephric excretory tubules form efferent ductules of
testis (connect rete testes to mesonephric duct)
•
Mesonephric (Wolffian) ducts virilize [under the
influence of testosterone]
- Elongate and become highly convoluted near efferent
ductules to form epididymis
- Obtain thick muscular coat to form vas deferens
- Outbudding produces seminal vesicle
Paramesonephric (Mullerian) duct regresses
- Influence of mullerian inhibiting substance (MIS,
anti-mullerian hormone)
•
!
Female: Uterus & uterine tubes
•
•
Mesonephric (Wolffian) duct regresses
Paramesonephric (Mullerian) duct forms genital ducts [stim by estrogens, no MIS]
•
Cranial vertical part & horizontal part of Mullerian duct develop into uterine tube
- Opens into abd cavity with funnel like structure: future fimbriae
Caudal vertical part of Mullerian duct forms uterine canal
- W lat folding, comes into close contact with paramesonephric duct fr opposite side
- Initially separated by septum but fuse later to form uterine canal
- Caudal tip projects into pos wall of urogenital sinus
- Surrounding mesenchyme forms myometrium
- Peritoneal covering froms perimetrium
Clinical: Congenital malformations may arise due to lack of fusion of paramesonephric
ducts.
•
•
NIGEL FONG 2011/2012
PAGE A235
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
Abnormalities:
Formation of broad ligament
•
•
•
Lateral folding results in urogenital ridge lying in transverse plane
Fusion of ducts in the midline creates transverse pelvic fold from lat sides of fused
paramesonephric ducts to lat walls of pelvis: broad ligament
Divides pelvic cavity into uterorectal pouch & uterovesical pouch
Female: Vagina
•
•
Upper part: derived from uterine canal (paramesonephros)
- Wing-like expansions around end of uterus: vaginal fornices
Lower part: from Sinovaginal bulbs
-
Solid evaginations from pelvic part of urogenital sinus form solid vaginal plate
Canalize by 5th month to form lower part of vagina
Lumen separated from urogenital sinus by hymen (develops thin opening for
menstrual fluid)
!
NIGEL FONG 2011/2012
PAGE A236
M1 NOTES IN GROSS ANATOMY
7 | PELVIS & PERINEUM
C. EXTERNAL GENITALIA
!
Indifferent genitalia
•
Week 3: mesenchyme migrates around cloacal memb to form elevated cloacal folds
- Cranial to cloacal mem: unite to form genital tubercle
Caudally, divided into urethral folds & anal folds when cloacal mem subdivided
into urogenital & anal mem (Week 6)
Genital (labioscrotal) swellings vis on either side of urethral folds (later form labia
maj / scrotum)
-
•
Female external genitalia
•
•
•
Genital tubercle elongates only slightly to form clitoris
Labia minora: from urethral folds, which do not fold
Labia majora: from genital swellings
Male external genitalia
•
•
•
•
•
Development influenced by androgens (esp. DHT) secreted by testes
- Clinical: Insufficient androgen stimulation results in micropenis
Rapid elongation of genital tubercle (called phallus) to form penis
- Pull urethral fold forward to form lat walls of urethral groove
- Endodermal epithelial lining of urethral folds forms urethral plate
- Urethral folds close over urethral plate to form penile urethra
Ectodermal cells later penetrate inward to form canal of ext urethral meatus
Genital (labioscrotal) swellings fuse in midline to form scrotal folds
Clinical: Hypospadas: Abnormal fushion of urethral folds results in abnormal urethral
opening e.g. on undersurface of penile shaft instead of at ext urethral meatus
!
NIGEL FONG 2011/2012
PAGE A237
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
CHAPTER 8: NORMAL STRUCTURE, DEVELOPMENT, AND NEUROANATOMY OF THE
8 | BRAIN, HEAD & NECK
!
!
1. NECK
!
A. EMBRYOLOGY: THE PHARYNGEAL APPARATUS
!
Early development
•
•
Development occurs around the cranial-most portion of the gut: the pharyngeal gut
- Resemble gills of a fish
Develop in 4th week as neural crest cells migrate into head and neck region.
- Clinical: Cranofacial anomalies due to disruption of neural crest cells is associated
with cardiac abnormalities since these cells are also involved in outflow tract
development.
The pharyngeal (brachial) arches
•
Pharyngeal arches appear as ridges on either side of the head & neck regions
- Arches: bars of mesoderm that give muscles, vessels, and skeleton
-
Pouches: endodermal diverticula from the gut, tends to become glands
Clefts: inward ectodermal grooves
-
Pharyngeal membranes: where ectoderm come close to meeting (but do not meet)
endoderm between the arches. In fishes, ectoderm and endoderm meet, resulting in
the membrane breaking down to form gill slits
NIGEL FONG 2011/2012
PAGE A238
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
B. DERIVATIVES
Derivatives of arches
•
•
6 arches form but arch 5 undergo regression, leaving 1, 2, 3, 4, 6.
Each arch supplied by its own cranial nerve and branch of aorta.
!
ARCH
NERVE
MUSCLE
SKELETON
1
Trigeminal (CN V)
Muscles of mastication,
mylohyoid
Maxilla, zygomatic, temporal
bone (part), mandible.
Malleus, incus
2
Facial (CN VII)
Muscles of facial expression
inc. platysma
Stapes
Hyoid, upper part
3
Glossopharyngeal
(CN IX)
Stylopharyngeus
Hyoid, lower part
4
Vagus (CN X): sup
laryngeal br
Cricothyroid, levator palatine,
constrictors of pharynx
Laryngeal cartilages: thyroid,
cricoid, etc
6
Vagus (CN X):
recurrent laryngeal br
Intrinsic muscles of larynx
!
!
!
!
Derivatives of clefts
•
Dorsal part of first cleft becomes ext auditory meatus
- Ext ear develops in a complicated manner from 1st and 2nd arch
•
2nd pharyngeal arch proliferates and
overlap 3rd & 4th arches. As the overgrowing 2nd
arch merges with the epicardial ridge in lower
neck, the more caudal clefts are obliterated
- Hence platysma migrated down
Improper development of 2nd arch results in
deformities in the ant ∆ of neck
- Pharyngeal cysts: if still secretory
•
-
Pharyngeal sinuses: blind-ended passages,
esp tends to open from palatine tonsil
Pharyngeal fistulae: communications with
the pharynx
Note: if in ant midline, likely to be a problem with thyroid devt instead
NIGEL FONG 2011/2012
!
PAGE A239
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Derivatives of pouches
•
•
•
Due to obliteration of 5th arch, pouches 4+5
combine. So there are pouches 1, 2, 3, 4+5
Each pouch divided into dorsal and ventral
component
Clinical: Ectopic thymic and parathyroid
tissue (as accessory glands or remnants) are
not uncommon, due to long migratory path
of glandular tissue
!
POUCH
!
VENTRAL
DORSAL
1
Regress
Forms stalk-like diverticulum, contacts
epithelial lining of 1st pharyngeal cleft (future
ext auditory meatus)
Gives eustachian tube, middle ear
2
Palatine tonsil (with mesodermal
infiltration but no change of site)
Regress
Pouches 3, 4+5 proliferate, detach from pharynx, and migrate anterioinferiorly
3
Forms thymus
Forms inf parathyroid
4+5
Gives parafollicular cells of thyroid
Forms sup parathyroid
C. REGIONS OF HEAD
NIGEL FONG 2011/2012
PAGE A240
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
B. ORGANIZATION & FASCIA
!
Organization of the neck
•
•
Neck lies btw lower margin of mandible & upper border of clavicles (and jugular notch)
- Function: conduit for structures btw head & trunk
Divided into 4 compartments:
- Superficial muscular layer (ant & pos)
- Ant visceral compartment: thyroid, digestive & respiratory sys
-
Paired vascular compartments: common carotid art, int jugular vein, vagus n
-
Pos vertebral compartment: also inc. cervical nerves & brachial plexus
!
Fascia of the neck
•
•
•
Func: Support, allow strs to slide over each other, and limit spread of infections
Superficial fascia: encloses platysma, embedded w superficial n, veins & lymph nodes
Investing fascia: encircles the neck
-
•
Splits to enclose trapezius & sternocleidomastoid
Inferiorly splits to attach to ant/pos surf of manubrium, leaving a suprasternal
space between the two layers.
Pretracheal fascia: surrounds thyroid, trachea, esophagus
•
- Inferiorly, blends with fibrous pericardium
Prevertebral fascia: surrounds prevertebral muscles & vertebral column
•
- Extends lat as the axillary sheath, surrounding axillary vessels & brachial plexus
- Retropharyngeal space btw prevertebral & pretracheal (buccopharyngeal fascia)
Carotid sheath: contains vascular compartment, blends with adjacent layers
NIGEL FONG 2011/2012
PAGE A241
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
C. MUSCULOSKELETAL STRUCTURES OF THE NECK
!
Bones
•
•
Typical cervical vertebrae (C3-6):
- small vertebral body
- foramina transversaria in their transverse
processes through which vertebral vessels
travel
Hyoid bone is suspended btw mandible &
thyroid cartilage, isolated from rest of skeleton
- Serves as attachment for ant neck muscles
and a prop to keep airway open
!
Anterior wall landmarks
•
•
•
•
•
Sternocleidomastoid divides ant/pos triangles
C3: Hyoid bone
C4: Top of thyroid cartilage (laryngeal prominence)
- More prominent in males, forms ‘Adam’s Apple’
C6: Cricoid cartilage
Emergency needle cricothyrotomy to access lower
airway when upper airway blocked
- Insert wide-bore needle thru cricothyroid
ligament (mem), which forms a soft depression
btw inf margin of thyroid cartilage & sup margin
of cricoid cartilage.
!
!
Muscles
•
•
Platysma is an extension of fascial muscles and shares common nerve supply by facial n
Sternocleidomastoid is a key muscle
- Unilateral contraction tilts head towards same side and rotates head to opp side
- Bilateral contraction flexes lower part of cervical spine (flex neck) and extends
upper part (extension of atlanto-occipital joint, tilts jaw up)
- Also accessory muscle of respiration; prominent SCM indicates respiratory distress
- Int jugular vein accessible through gap between SCM heads
NIGEL FONG 2011/2012
PAGE A242
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
!
MUSCLE
NERVE
ORIGIN
INSERTION
ACTION
Inf border of mandible
Fascia over pectoralis maj
& deltoid
Tenses skin,
express grimace
Mastoid process, temporal
bone
Sternal head: manubrium
Clavicular h: med 1/3 clav
Flex neck or
rotate head to
opp side
Sup nuchal line
Ext occipital protuberance
Ligamentum nuchae, C7T12 spinous proc
Clavicle: lat 1/3
Scapula: spine, acromion
Elevate, depress,
superiorly rotate,
or retract scapula
(see upper limb)
Superficial layer:
Facial
(CN 7)
Platysma
Middle layer:
Sternocleidomastoid
Trapezius
Accessory
(CN 11)
Deep layers, ant triangle: infrahyoid muscles: (named after attachments)
Omohyoid
Sternohyoid
Sternothyroid
Ansa
cervicalis
C1-3
Thyrohyoid
C1
Sup scapula
Manubrium of
sternum
2 bellies
Superficial
Thyroid cartilage
Deeper
Hyoid bone
Depress hyoid
Thyroid cartilage
+ depress larynx
Hyoid bone
+ elevate larynx
Deep layers, pos triangle: prevertebral muscles: (other muscles here unimportant)
C4-6
C3-C6 transverse process
1st rib: scalene tubercle: ant
to subclavian art, pos to v
Cervical n
ant rami
C5-C7 tranverse process
1st rib: pos to subclavian art
Ant scalene
Middle scalene
Flex head,
elevates 1st rib
!
Torticollis (short sternocleidomastoid)
•
•
Head tilts towards and face turns away from affected side; cervical spine flexed
- If untreated: Assymetrical growth of face, cervical vertebrae become wedge-shape
Causes
- Congenital torticollis: tearing of SCM during difficult labour resulting in hematoma,
fibrosis, and shortening.
NIGEL FONG 2011/2012
PAGE A243
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
D. NEUROVASCULATURE OF ANT ∆: IDENTIFICATION & RELATIONS
[See blood supply of head & neck, cranial nerves for systematic description[
Overview
Superficial structures
•
External jugular vein: from behind angle of mandible to mid-clavicular point
•
Cutaneous nerves: from C2-C4 cervical plexus, emerging fr nerve root of neck at pos
border of sternocleidomastoid
- Lesser occipital n: ascends at SCM pos border to lat occipital region / med auricle
- Great auricular n: crosses SCM to supply angle of mandible, parotid, auricle
- Transverse cutaneous n: Passes forward to ant/lat neck
- Supraclavicular nerves: descend to chest wall & shoulder region down to rib 2
!!
NIGEL FONG 2011/2012
PAGE A244
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Carotid sheath
•
•
Relations in the carotid sheath
- [Lat] Internal jugular vein (and deep cervical lymph nodes)
- [Med] Carotid arteries
- [Pos] Vagus nerve
Common relations of carotid sheath contents:
- [Ant] Skin, fascia, sternocleidomastoid, omohyoid, parotid (int/ext carotid)
- [Pos] C4-7 transverse process, prevertebral muscles, cervical plexus, phrenic n
- [Med] Vascular compartment: Larynx, Pharynx, Trachea, Esophagus, Thyroid
Carotid sheath: surface anatomy
•
•
Surface marking: fr sternoclavicular joint to point midway between tip of mastoid
process and angle of mandible
Palpate carotid pulse: at bifurcation of common carotid artery
-
At ant border of sternocleidomastoid
Level of sup border of thyroid cartilage (C4)
!
NIGEL FONG 2011/2012
PAGE A245
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
E. NERVES IN POS ∆ / PREVERTEBRAL COMPARTMENT
!
!
!
Cervical plexus (C1-4)
•
•
•
There are 8 cervical spinal nerves but only 7 cervical vertebrae, C1 emerges sup to
vertebrae
Ant rami of C1-4 form irregular loops
- Ant/med to levator scapula & middle scalene muscles, deep to sternocleidomastoid
Cutaneous branches emerge from pos border of sternocleidomastoid (nerve point)
-
•
C1: no cutaneous branch
C2: back of scalp, auricle, angle of mandible (back of head above neck)
C3: whole neck / collar region
C4: Over shoulder
Clinical: front/sides of neck may be anesthetized by subcutaneous injection behind
midpoint of sternocleidomastoid. This also paralyzes the phrenic n
Ansa cervicalis (C1-3): loop of nerve fibres lying on int jugular vein
-
Sup root (C1-2) and inf root (C2-3)
Supplies neck muscles: prevertebral, levator scapulae, most strap muscles
Phrenic nerve in neck
.
.
ORIGIN
C3-5: forms at lat border of ant scalene at C4 level (upp border of thyroid cartilage)
• C5 may form accessory phrenic nerve and join later.
• Differentiation from Vagus n: vagus nerve continues up to the head
.
COURSE
.
TERM
.
BR
.
SS
Descends obliquely deep to prevertebral fascia, on surf of ant scalene, pos to carotid
sheath
Crosses root of neck in plane of ant scalene: ant to subclavian artery, pos to subclavian
vein. Enters thorax ant to int thoracic artery.
No branches.
• Muscular: diaphragm
• Sensory: pericardium, mediastinal parietal pleura, pleura & peritoneum covering
central diaphragm
!
NIGEL FONG 2011/2012
PAGE A246
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
Brachial plexus (C5-T1)
•
•
•
!
Ant rami C5-T1 forms roots of the brachial plexus, which supplies the upper limb
Emerge btw scalenus ant & medius, covered by prevertebral fascia & pos to int jugular
vein of carotid sheath (nerves are large and converging)
Descend inferolat, passing btw 1st rib, clavicle & sup border of scapula to enter axilla.
Accessory nerve (CN 11)
•
•
•
Cell bodies in C1-C6 spinal segments.
- Axons ascend, pass thru foramen magnum, exit cranial cavity thru jugular foramen.
- Leaves lat border of sternocleidomastoid (at junc of sup & middle thirds) and
passes within/deep to investing fascia, disappearing beneath ant border of trapezius
(at junc of middle & inf thirds).
LMN lesion: weakness in turning head to contralateral side, ipsilateral shoulder droop
UMN lesion: no signs seen due to bilateral cortical control
CRANIAL N
XI
(Spinal)
Accessory
FIBRE
SUPPLY
1º NEURON
2º NEURON
Som Mot
Sternocleidomastoid,
trapezius
Spinal accessory
nuc (in sp cord)
-
!
CN visible in pos ∆
•
•
Glossopharyngeal
(CN 9) to tongue
Hypoglossal (CN 12)
to base of tongue
!
!
NIGEL FONG 2011/2012
PAGE A247
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
F. ROOT OF THE NECK
Relations: Superficial to deep
•
•
•
•
•
Subclavian vein (not compressed by muscles)
Scalenus anterior & phrenic nerve
Subclavian artery
Brachial plexus
Apex of lung (pos to first part of subclavian art): beware of pneumothorax
!
!
Subclavian art
.
.
.
.
.
.
.
.
ORIGIN
COURSE
TERM
BRANCH
R: fr brachiocephalic art behind right sternoclavicular joint
L: fr arch of aorta directly, ascending to root of neck
1st part: From origin to med border of scalenus anterior muscle
2nd part: Behind scalenus anterior muscle
3rd part: From lat border of scalenus ant, across pos ∆ of neck to lat border of first rib.
Continues as axillary artery at lat border of 1st rib
1st part:
2
nd
part:
3rd part:
CLINICAL
Vertebral art
Asc through foramina transversaria of upper 6 ribs to
brain, forming basilar arteries [Supplies brain]
Thyrocervical art
Short trunk giving
- Inf thyroid art: to thyroid
- Sup cervical art: crosses brachial plexus
- Suprascapular art: follows suprascapular n
Int thoracic art
Descends into thorax
Costocervical trunk
Runs backward over dome of pleura, div into
- Sup intercostal art: to 1st & 2nd intercostal space
- Deep cervical art: to deep muscles of neck
No branches
Compression of subclavian artery against upper surface of first rib can stop upper limb
hemorrhage
!
NIGEL FONG 2011/2012
!
PAGE A248
M1 NOTES IN GROSS ANATOMY
CLINICAL
8 | BRAIN, HEAD & NECK
Collateral circulation of the subclavian artery:
• Scapular anastomosis: btw 1st part subclavian art & 3rd part axillary art
- 1st part subclavian - thyrocervical trunk - suprascapular art - dorsal scapular art
- circumflex scapular art - subscapular art - 3rd part axillary art
• Btw int thoracic & pos intercostal art
- 1st part subclavian - thyrocervical trunk – int thoracic - pos intercostal art –
circumflex scapular art (anatomosis) – 3rd part axillary art
• Btw ext carotid & 2nd part of subclavian art
- Ext carotid - occipital art - deep cervical art - costocervical trunk – 2nd part
subclavian art
Slow occlusion of axillary artery often enables sufficient collateral circulation to develop,
sudden occlusion does not. However axillary art has inadequate collateral circulation btw
origin of subscapular artery & deep artery of arm
!
Subclavian vein
•
•
Continuation of axillary vein fr lat border of 1st rib, travels ant to sternocleidomastoid
Unites with int jugular vein (venous angle) to form brachiocephalic vein
•
Receives
- External jugular vein as only named tributary
- At venous angle: thoracic duct (L) or right lymphatic duct (R)
Central venous line catherization through subclavian vein
•
-
Insert needle at lower border of clavicle, at junc of medial third and outer 2/3,
where pos border of sternocleidomastoid inserts.
Direct needle pos & up to avoid first rib, but not too upwards or it will hit clavicle
Bright red blood and pulsatile resistance indicates that the subclavian art has been
entered instead
Possible complications include pneumothorax, hemothorax (damage to subclavian
vein), int thoracic art injury, or phrenic nerve injury (diaphragmatic paralysis)
NIGEL FONG 2011/2012
PAGE A249
M1 NOTES IN GROSS ANATOMY
Cervical sympathetic trunk
•
•
-
•
!
Lies medial to vagus, in deep fascia btw carotid sheath & prevertebral fascia.
Consists of 3 ganglia
- Sup cervical ganglion: immediately below skull (C1)
-
•
8 | BRAIN, HEAD & NECK
Middle cervical ganglion: at cricoid cartilage
Inf cervical ganglion: btw C7 vertebra & first rib, often fuses with first thoracic
ganglion to form stellate ganglion
- Ansa subclavia (hooks ard subclavian art) connects middle to inf cervical ganglion
Supplies:
- All ganglia: gray rami to cervical nerves ant rami
- All ganglia: Cardiac branches from all 3 ganglia descend to supply heart
- Sup ganglia: carotid plexus, pharyngeal plexus, branches to CN 9, 10, 12
- Middle ganglia: thyroid branches
Effects of sympathetic disruption (Horner’s syndrome) see eye.
Nerves in root of neck
•
•
•
Phrenic nerves: pass btw subclavian
arteries & veins, under prevertebral fascia
Vagus nerve: passes ant to first part of
subclavian art, pos to brachiocephalic vein
Recurrent laryngeal nerves: ascend in
tracheo-esophageal groove
!
!
NIGEL FONG 2011/2012
PAGE A250
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
G. NECK VISCERA
!
!
Trachea
LOC
Continuation of larynx at lower border of cricoid cartilage (C6)
Descends in midline and ends in thorax at the carina by dividing into principal bronchi at
the sternal angle (T4/5)
ANT
Skin, fascia, jugular arch, sternothyroid & sternohyoid muscles
Isthmus of thyroid gland (2nd-4th ring), inf thyroid vein, thyroid ima art
POS
Esophagus, Recurrent laryngeal nerves
LAT
Thyroid gland, carotid sheath
STR
Fibroelastic tube with kept open by C-shaped hyaline cartilage rings
• Cartilage rings are deficient posteriorly and connected by smooth trachealis muscle
FUNC
BLOOD
NERVE
CLIN
Airway for respiration
BLOOD
Inf thyroid art, bronchial arteries
LYM
Pretracheal & paratracheal nodes, deep cervical lymph nodes
Vagus nerves, recurrent laryngeal nerves.
Deviation from the midline indicates pathology e.g. tension pneumothorax
Cricothyroidotomy: insertion needle btw inf margin of thyroid cartilage & sup margin
of cricoid cartilage (cricothyroid membrane) allows emergency airway access
Tracheostomy: insertion of tracheostomy tube via midline incision from cricothyroid
membrane, entering trachea btw 1st / 2nd tracheal rings, or through 2nd-4th rings. Avoid:
• Avoid: inf thyroid veins, thyroid ima art, L brachiocephalic vein, jugular venous arch,
pleurae, thymus
• Do not cut through pos wall and damage the esophagus (esp in children/infants)
• Avoid damage to recurrent laryngeal nerves
!
!
NIGEL FONG 2011/2012
PAGE A251
M1 NOTES IN GROSS ANATOMY
!
8 | BRAIN, HEAD & NECK
Thyroid gland
LOC
!
Located anteriorly in neck, fr C5-T1 vertebrae
In vascular compartment of ant neck, surrounded by pretracheal layer of fascia
ANT
Sternocleidomastoid, Strap muscles: sternothyroid, omohyoid, sternohyoid
POS/LAT
Carotid sheath: common carotid art, int jugular vein, vagus n
POS/MED
Larynx, trachea, pharynx, esophagus
• Cricothyroid & ext laryngeal nerve
• Recurrent laryngeal nerve btw esophagus & trachea
STR
FUNC
BLOOD
NERVE
CLIN
Right and left pear-shaped lobes
Isthmus: narrow connection of R/L lobes over the
trachea (ant to 2nd/3rd tracheal ring)
Pyramidal lobe: (if present) proj upwards fr isthmus
Parathyroid glands (4): embedded in pos surface,
paired sup & inf
Endocrine gland: see physiology
ART
•
• Sup thyroid art: descends fr ext carotid art (accom. by ext laryngeal nerve)
• Inf thyroid art: fr thyrocervical trunk, asc behind gland to cricoid cartilage,
then turns medially & downwards (related to rec laryngeal nerve)
• Thyroid ima art (10% of people): small unpaired, on ant surface of trachea
VEN
• Sup thyroid vein: follows sup thyroid art, drains to int jugular vein
• Middle thyroid vein: to int jugular vein
• Inf thyroid vein: L/R join and descend in front of trachea, draining into L
brachiocephalic vein
LYM
Mainly to deep cervical lymph nodes, also to paratracheal nodes
Cervical sympathetic ganglia; nerve supply is minor, mainly under hormonal control.
• Due to pretracheal fascia, thyroid gland follows movements of larynx when swallowing:
moves upwards when swallows.
• Note related nerves of thyroid arteries: may be damaged in procedures: ligate the sup
thyroid artery close to gland, and the inf thyroid art away from gland
• Thyroidectomy: pos part of each lobe usually preserved, to protect recurrent & sup
laryngeal nerves and spare parathyroid glands.
• Enlarged thyroid compresses airway, resulting in stridor (noisy breathing)
NIGEL FONG 2011/2012
PAGE A252
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
REG
Thyroid
MODE
CT Transverse
COND
Thyroid gland carcinoma,
with trachea invasion
VIS
NOTE
Embryology of the thyroid gland & related defects
•
Thyroid migrates from tongue to neck
- Grows from endodermal thickening in midline floor of pharynx behind 1st arch
(future ant 2/3 of tongue)
- Thyroglossal duct (a diverticulum) grows caudally in the midline (sup to skeletal
components) to the thyroid cartilage
- Distal end proliferates to form 2 lobes and become solid glandular tissue
- Pbarathyroid & parafollicular cells develop separately from pharyngeal pouches
•
Adult remnants:
- Proximal tubular part of thyroglossal duct
(from tongue to thyroid) degenerates
- Site of origin of thyroglossal duct remains as
the foramen cecum (a pit) at junc of ant
2/3 and pos 1/3 of tongue
Incomplete descent forms ectopic thyroid gland
- Thyroid may be arrested at any point btw
base of tongue and trachea
- Most commonly, forming lingual thyroid
Persistent thyroglossal duct may form cysts
- Impt to differentiate btw ectopic thyroid
gland (only thyroid tissue present) and a
cyst, when excising cyst
•
•
!
!
!
!
NIGEL FONG 2011/2012
!
!
!
PAGE A253
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
2. FACE & SCALP
!
A. LAYERS & MUSCLES
Scalp
•
•
•
Functionally, scalp extends till the supercillary arches (eyebrows)
Occipitofrontalis muscle forms a common tendon (epicranial aponeurosis) between
occipital and frontal bellies.
- Aponeurosis forms a layer of the scalp, diving the connective tissue layer into two
- Contraction of the occipitofrontalis elevates eyebrows and gives a surprised look
- Botox paralyses the frontalis, so no lines appear on the forehead
5 layers: Skin, dense connective tissue, aponeurosis, loose connective tissue, pericranium
- First 3 layers may move freely over the loose connective tissue layer.
- Due to aponeurosis, sup. scalp wounds do not gape, but deep ones gape widely
- If hair gets caught, face can be pulled off
!
Face
•
•
•
Face = ant aspect of head from forehead to chin, partially including either ear
Muscles of facial expression are subcutaneous, with origin from bone/fascia, and
insertion into the skin. There is no deep fascia in the face.
- Unusual - only other subcutaneous muscles are that of the scrotum
- Creases on skin develop perpendicular to the direction of contracting facial muscles.
- Develop from mesoderm of 2nd pharyngeal arch
- SS by facial nerve (CN VII) – except opening of eyelid (levator palpebrae sup)
Sphincters close orifices:
-
•
•
Orbicularis oris closes the mouth
Orbicularis oculi closes the eyes (orbital part tightly, palpebral part gently), which
is nec to protect the eyeballs from injury, and spread tears to keep the cornea moist
Dilators open orifices
- Elevators, e.g. Zygomaticus maj, which gives a smile
- Depressors, e.g. depressor anguli oris, which pulls the corners of the lips down
Masseter (not a muscle of facial expression) and buccinator (deep to masseter) are impt
landmarks
NIGEL FONG 2011/2012
PAGE A254
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
!!
!
NIGEL FONG 2011/2012
PAGE A255
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
B. BLOOD SUPPLY
!
Blood supply of face: Facial artery
.
.
ORIGIN
.
COURSE
.
TERM
Ext carotid artery (3rd branch after sup thyroid & lingual art)
Arches up & over submandibular gland (may appear attached)
Curves around inf margin of mandible at the ant border of masseter musc
Tortuous course: Runs towards angle of mouth, side of nose, medial angle of eye
Anastomose w opthalmic artery (fr int carotid)
Anastomose across the midline
.
BR
.
SS
CLIN
Submental artery, Inf labial art, Sup labial art, Lat nasal art, Transverse facial art
Face
Facial pulse palpable at inf border of mandible, ant to masseter
!
Blood supply of face: others
•
•
•
•
!
Sup temporal artery (which branches to give transverse facial artery) fr ext carotid
Mental artery: term br of inf alveolar artery (fr ext carotid)
Supraorbital & supratrochlear arteries (accompanying their nerves): fr ophthalmic art,
which arises fr int carotid
Clinical: When cut, vessels of the face bleed from both ends due to rich anastomosis. It
is necessary to ligate both ends during surgery.
Blood supply of scalp:
•
•
•
•
•
Fr ext carotid art : via occipital, pos auricular, sup temporal art
Fr int carotid art : via supratrochlear & supra-orbital art
Calvaria is supplied by meningeal arteries.
Clinical: Arteries of scalp bleed profusely when cut as they are firmly attached to dense
connective tissue, and do not vasospasm when injured.
Clinical: Bleeding of the scalp can be stopped by application of circumferential pressure
(encircle head tightly above ear & eyebrows) as all sup art to scalp ascend from the
face & neck
!
NIGEL FONG 2011/2012
PAGE A256
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
!
Venous drainage of face
•
•
•
Danger triangle of face
Thru accompanying veins, facial vein draining into int jugular vein
- Identification: facial vein lies behind facial art and is not tortuous
Communications w venous sinuses of the cranium
- W cavernous sinus thru sup opthalmic vein
- W pterygoid venous plexus thru inf opthalmic & deep facial veins
Infections of face can spread into cranial cavity since facial veins are valveless
- Esp. in the danger triangle (fr upper lips to bridge of nose)
B. TRIGEMINAL NERVE (CN V)
!
CRANIAL N
V
V1
V2
V3
V3
Trigeminal
Opthalmic
Maxillary
Mandibular
Mandibular
FIBRE
SUPPLY
1º NEURON
2º NEURON
Som Sen
Face, ant to vertex ear chin
- Cornea, forehead & scalp
- Cheek, upper jaw
- Chin, lower jaw, ant 1/3
tongue
Trigeminal
ganglion
Dpd on modality:
Principal sens nc
Mesencephalic nc
Spinal nuc of V
Som Mot
Mus of mastication, tensors
tympani, palatini, digastric
(ant belly), mylohyoid
Trigeminal motor
nuc
-
!
Trigemino-Thalamic system
•
•
Similar to ascending spinal tracts:
- 1º (trigeminal) ganglion contain
pseudo-unipolar neurons
- 2º neuron decussates
- 3º neuron is in the thalamus
Differences
- CN V goes to thalamus VPM
(ventro-posteromedial
nucleus)
while spinal tracts goes to VPL
(ventro-posteromedial nucleus)
- Little overlap btw V1, V2, V3 but
spinal dermatomes do
NIGEL FONG 2011/2012
!
PAGE A257
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Nuclei
•
•
Motor nuc: trigeminal motor nuc (pons)
Sensory nucleus segregated by modality
- Spinal nuc of V is shared by CN V, VII, IX, X,
receiving pain & temperature fibres from all CN
- Mesencephalic nuc is exception: contains 1º neu.
MODALITY
Like spinothalamic:
Pain, Temp, Crude touch
Like DCML:
Discriminative touch, vibration, pressure
Conscious proprioception fr muscles of
mastication, TMJ
1º NEURON
Trigeminal
ganglion
!
2º NEURON
LOCATION
Spinal nuc of V
Stretch fr medulla to
upper cerv spinal cord
Principal (Chief)
sensory nuc
Pons
Mesencephalic nuc
in CNS but contains 1º neurons
Midbrain
!
Course & division
•
Emerges from pons. Distal to trigeminal gangliion, splits into
- Opthalmic n (CN V1)
: exit skull via sup orbital fissure
-
Maxillary n (CN V2)
Mandibular n (CN V3)
: exit skull via foramen rotundum
: exit skull via foramen ovale
-
•
•
Terminal cutaneous branches: Supraorbital (V1), infraorbital (V2) & mental (V3) n
may be visible coming out through their foramina
Motor root passes inf to trigeminal ganglion (bypassing ganglion), joining mandibular n
CN V has no presynaptic parasympathetics fr CNS, but postsynaptic parasympathetic
fibres of other CN join branches of CN V to be carried to their destinations
NIGEL FONG 2011/2012
PAGE A258
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Supply of CN V
•
•
Somatic sensory: SS face ant to vertex, ear, and chin.
- V1: skin of forehead, upper eyelid, conjunctiva, cornea, nosebridge, dura
- V2: cheeks, nasal cavity (and maxillary sinus), upper jaw
- V3: lower jaw, ant 2/3 tongue, ext auditory meatus, ext tympanic membrane
- V3 also carries proprioception information from lower jaw
- Scalp – note trigeminal supplies ant to ear & vertex, C2/3 posteriorly
- Clinical: test patient laterally since it is still CN V1 on tip of nose
Motor division supplies muscles of mastication (masseter, temporalis, pterygoids)
Clinical notes
•
•
•
•
•
Jaw jerk reflex: tap chin w downward stroke elicits twitch of jaw-closing muscles
- Input fr muscle spindles (via CN V3) relayed via mesencephalic nuc to motor nuc
LMN lesion: unilateral bite weakness, sensory loss
UMN lesion: minimal effect due to bilateral cortical control (general principle for CN)
Trigeminal neuralgia (tic douloureux): paroxysmal excruciating pain in territory
supplied by a CN V division, causing grimacing
- Often precipitated by activating trigger zone: e.g. chewing or touching nose/cheek
- Demyelination of sensory root of n, exposed axons touch unmyelinated pain fibres
- Cause: compression of n by blood vessel
Herpes simplex virus may remain latent in trigeminal ganglia, coursing through
trigeminal branches to give cold sores.
!
NIGEL FONG 2011/2012
PAGE A259
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
C. FACIAL NERVE (CN VII)
!
CRANIAL N
VII
Facial
FIBRE
Som Mot
Parasym
SUPPLY
1º NEURON
2º NEURON
Musc of facial expression,
stapedius, stylohyoid,
digastric (pos belly)
Facial motor nuc
-
Lacrimal gland
Lacrimal nuc
Pterygopalatine
Submandibular, sublingual
Salivatory nuc
Submandibular g
Geniculate gang.
Nucleus tractus
solitarius
Spec Sen
Taste: Ant 2/3 of tongue
Som Sen
Ext ear (via intemediate n)
Spinal nuc of V
Course of CN VII
•
•
Motor root loops around abducens nucleus
Emerge fr pontomedullary junction in pos cranial fossa as
- Larger motor root
- Nervus intemedius: carries all non-motor fibres
•
Enters int acoustic meatus, travels in facial canal inside
temporal bone
- At the geniculum, CN VII turns abruptly pos to
course along med wall of tympanic cavity
- Gives branches: n to stapedius, greater petrosal n,
chorda tympani
Facial n & trigeminal n (with
large trigeminal ganglion)
14: Chorda tympani
!
!
!
CN VII motor division
•
•
Emerges fr stylomastoid foramen of temporal bone
- Immediately supplies pos belly of occipitofrontalis, stylohyoid, pos belly digastric
Travels in parotid gland (sup to veins & arteries), then branching into
- Posterior auricular n: to back of scalp
- Temporal br: cross zygomatic arch, to orbicularis occuli & supraorbital musc
-
Zygomatic br: passes inf to eye, to orbicularis occuli & infraorbital musc
Buccal br: Ext to buccinator, to upper lip musc
-
(Marginal) mandibular br: along mandible, to lower lip musc
-
Cervical br: to platysma
NIGEL FONG 2011/2012
PAGE A260
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Nervus Intemedius
•
•
•
Greater petrosal n leaves CN VII in facial canal, join
lacrimal n (fr CN V1).
- Parasympathetic to lacrimal gland, nasal glands.
Synapse in pterygopalatine ganglion
Chorda tympani: leaves CN VII in facial canal, joining
lingual n (fr CN V3)
- Parasym to submandibular & sublingual gland
Synapse in submandibular ganglion
- Taste fibres fr ant 2/3 of tongue.
Sensory fibres: 1º cell bodies at geniculate ganglion in
geniculum of CN VII
!
!
Bell’s Palsy: Lower motor neuron lesion
•
•
•
Causes (can be sudden onset of unclear etiology)
- Inflammation of facial nerve (e.g. viral neuritis) esp at stylomastoid foramen
- Temporal bone fracture, wounds (superficial, hence vulnerable), birth injury
LMN lesion causes ipsilateral paralysis of facial muscles (both upper & lower face)
- Loss of tonus of orbicularis oculi: inf eyelid everts, lacrimal fluid not spread over
cornea, making cornea vulnerable to ulceration
- Angle of mouth sags on affected side
- Dribble of food & saliva from mouth; impaired labial (B, M, P, W) sounds
If lesion occurs before these fibres exit, may also result in
- Ipsilateral hyperacusis: over-sensitivity to sound due to stapedius paralysis (which
dampens sounds)
- Ipsilateral loss of salivation & tearing
- Ipsilateral loss of taste in ant 2/3 of tongue
Upper motor neuron lesion
•
•
Corticobulbar tract to muscles on lower face receive only contralateral UMN influence.
- Exception to rule that cranial nerves generally receive bilateral UMN influence
- Hence CN VII UMN lesion observable, while rest of cranial nerves not so.
UMN lesion causes paralysis of lower half of contralateral face
- Forehead innervated bilaterally and is unaffected (still wrinkles)
NIGEL FONG 2011/2012
PAGE A261
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
D. PAROTID GLAND
.
.
LOC
.
Btw ramus of mandible & ant border of sternocleidomastoid
ANT/MED
Masseter, temporomandibular joint, pos border mandible medial pterygoid
POS/MED
Mastoid proc, Sternocleidomastoid, Pos belly digastric, Styloid proc & musc,
Carotid sheath [ICA, IJV, CN X], CN IX, XI, XII, Pharynx.
SUP
Ext auditory meatus
.
Thick duct emptying secretions into mouth (parotid papilla opposite 2nd upper molar)
• Surface mark: middle 1/3 of line connecting intertragic notch of ear to upper border of lip
DUCT•
.
.
FUNC
.
Serous secretion
.
NERVE
CLIN
Parasympathetic:
• Fr glossopharyngeal (CN IX), via lesser petrosal n (CN IX parasym only SS parotid)
• Synapsing in otic ganglion
• Continuing along parotid branches of auriculotemporal nerve (CN V3)
• Malignant tumours in the parotid gland may involve facial nerve
• Inflammation: may result fr retrograde bact infection fr mouth, or mumps etc
• Frey’s syndrome: Arises following penetrating wound damage to auriculotemporal
(parasympathetic SS) and great auricular nerves. During healing, parasympathetic
fibres of auriculotemporal nerves grow to join the great auricular nerve, reaching sweat
glands of skin, such that parasympathetic stimuli for saliva production during eating
results in beads of perspiration on skin instead.
!
Relations in the parotid gland
•
•
Travelling within gland [Sup-Deep]:
- Facial nerve,
- Retromandibular vein
- Ext carotid artery
Easily damaged during surgery on parotid
NIGEL FONG 2011/2012
!
PAGE A262
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
3. BLOOD SUPPLY OF THE HEAD & NECK
!
A. ARTERIAL SUPPLY
!
Common carotid artery
.
.
ORIGIN
R common carotid: fr brachiocephalic art behind R sternoclavicular jt
L common carotid: fr arch of aorta in sup mediastinum
.
COURSE
Runs upward in carotid sheath fr SC jt, under ant border of sternocleidomastoid
No branches; bifurcates into ext & int carotid art at upper border of thyroid cartilage
.
.
..adf
RELATION
ANT
Skin, fascia, sternocleidomastoid, strap muscles
POS
C4-7 transverse process, prevertebral muscles, sympathetic trunk
MED
Larynx, pharynx, trachea, esophagus, thyroid
LAT
Int jugular vein, vagus nerve
.
.
SINUS
Carotid sinus: localized dilation at the carotid bifurcation
• Baroreceptor for arterial pressure
Carotid body: pos to bifurcation of common carotid
• Chemoreceptor for PO2 & PCO2
• SS: CN XI (glossopharyngeal)
.
SS
.
CLINICAL
All structures in head & neck, except pos brain which is SS by vertebrobasilar system
Carotid pulse point at its bifurcation – ant border of sternocleidomastoid, at level of
sup border of thyroid cartilage (C4)
Collateral circulation of common carotid artery:
!
• Btw thyroid arteries: subclavian art – thyrocervical art – inf thyroid art – sup
thyroid art – ext carotid art
• Btw ext carotid & 2nd part of subclavian art: ext carotid - occipital art - deep
cervical art - costocervical trunk – 2nd part subclavian art
• Btw L/R sides of face/scalp
• Fr vertebral art via Circle of Willis
NIGEL FONG 2011/2012
PAGE A263
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
External Carotid artery
.
.
ORIGIN
.
COURSE
Terminal branch of common carotid artery at upper border of thyroid cartilage (C4)
Ascend superficially upon emerging from ant border of sternocleidomastoid
•
•
•
•
Initially med then pos/lat to int carotid art
Med to int jugular v [see relations in carotid sheath]
Crossed by CN XII, pos belly digastric, stylohyoid
Stylopharyngeus, CN XII, CN X pharyngeal br pass btw ECA & ICA
BR
BR
3 med:
2 pos:
1 ant:
Sup thyroid art:
Descends to upper pole of thyroid w ext laryngeal n
Lingual art:
Passes fwd to tongue
Facial art:
Supply face, tonsil, submandibular gland [see face]
Occipital art:
Ascends pos to mastoid proc to back of scalp
Pos auricular art:
Supplies auricle & scalp
Ascending pharyngeal:
Ascends to & supplies pharyngeal wall
.
.
TERM
Terminates in substance of parotid gland [deep to facial n] by bifurcating into
• Sup temporal art: ascend over zygomatic arch to supply scalp
• Maxillary art: runs fwd/med to neck of mandible and enters pterygopalatine fossa
[see maxilla]. Gives middle meningeal art: enters skull through foramen spinosum
.
Neck, face, scalp, tongue, maxilla.
SS
.
CLINICAL
Ext carotid can be ligated without consequence due to rich retrograde collateral supply
between branches & contralateral side (e.g. occipital art)
!
Internal Carotid artery
.
.
ORIGIN
.
COURSE
Terminal branch of common carotid artery at upper border of thyroid cartilage (C4)
Ascend in neck, embedded in carotid sheath deep to parotid gland [relations: see neck]
Passes through carotid canal in pterous part of temporal bone (middle cranial fossa)
Travel upwards & forwards in cavernous sinus (without communication)
Leaves sinus and travels up med to ant clinoid process of sphenoid bone
Incline backwards, lat to optic chiasma
BR
BR
No branches in neck, all branches in skull
• Ophthalmic art: enters orbit through optic canal, also gives ctrl art of retina
• Pos communicating art: to pos cerebral art [part of Circle of Willis]
.
.
Bifurcates into Ant & Middle cerebral art [see blood supply of brain]
TERM
.
Brain, orbit & supraorbital region, part of nose
SS
.
CLINICAL
See blood supply of brain
!
Common surface marking
•
All structures of carotid sheath:
- fr sternoclavicular joint
- to point midway between tip of mastoid process and angle of mandible
NIGEL FONG 2011/2012
PAGE A264
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
B. VENOUS DRAINAGE
!
!
External Jugular vein
.
.
ORIGIN
!
Forms behind angle of mandible by union of
• Pos auricular vein
• Pos division of retromandibular vein (fr union of sup temporal & maxillary vein)
.
COURSE
.
TERM
Descends obliquely ant to sternocleidomastoid, pos to platysma [note surf marking]
Pierce deep fascia abv midpoint of clavicle in pos triangle to drain into subclavian v
.
RECV
.
DRAINS
.
CLINICAL
•
•
•
•
Pos ext jugular vein: fr back of scalp
Transverse cervical vein: fr skin/fascia over pos triangle of neck
Suprascapular vein: fr back of scapula
Ant jugular vein: in front of neck close to midline
Drain blood from scalp and side of face
• Jugular venous pressure visible (see physiology)
• EJV severence: investing neck fascia holds lumen open, –ve intrathoracic pressure
sucks air in, prod venous air embolism (froth in R heart): stop blood flow, dyspnea
Internal Jugular vein
.
.
ORIGIN
.
TERM
Continuation of sigmoid sinus, leaving skull through jugular foramen (pos cranial fossa)
Descends in neck through carotid sheath (together w deep cervical lymph nodes)
• Inferior bulb (dilation) of IJV has bicuspid valve to prevent backflow e.g. if inverted
Behind medial end of clavicle: joins subclavian to form brachiocephalic v
.
.
..adf
RELATION
ANT
Skin, fascia, sternocleidomastoid, strap muscles, parotid gland, cross by CN XI
POS
C4-7 transverse process, prevertebral muscles, sympathetic trunk, phrenic n
MED
Int/common carotid art, CN X. Superiorly, CN IX-XII also.
.
.
RECV
.
DRAINS
• Inf petrosal sinus (sup sinus drains to cavernous sinus directly)
• Facial vein (also revc ant division retromandibular v), pharyngeal veins, lingual vein
• Sup thyroid vein, middle thyroid vein
Brain, ant face, cervical viscera, deep muscles of neck
.
CLINICAL
Can catheterize IJV btw sternal & clavicular heads of sternocleidomastoid. Palpate
common carotid art and insert needle lateral to art, pointing downwards
NIGEL FONG 2011/2012
PAGE A265
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
C. LYMPHATICS
!
!
!
Pericervical collar
•
•
•
Pericervical collar of nodes extending from below chin to back of head
Superficial ring:
- Occipital
: drain back of scalp
- Mastoid
: drain scalp above ear, auricle, ext auditory meatus
- Parotid
: drain scalp abv parotid, eyelids, parotid, ext audit m
- Buccal (facial)
: drain face (lymph fr here passes into submandibular)
- Submandibular
: drain front of scalp, nose & sinuses, cheek, upper lip,
most teeth, ant 2/3 of tongue, floor of mouth, gums
- Submental
: drain tongue, ant mouth floor, lower incisors, lower lip, chin
- Superficial cervical : drain angle of jaw, lower parotid, earlobe (along EJV)
Deep nodes of regional collar:
- Retropharyngeal
: drain nasopharynx, auditory tube, vertebral column
- Laryngeal
: larynx (ant to larynx)
- (para)Tracheal
: Drain trachea, thyroid
Deep cervical nodes
•
•
•
•
Lie along IJV within carotid sheath.
Receive lymph from all groups of regional nodes.
Efferent lymphatics form jugular trunk, draining into thoracic duct / R lymphatic duct
Clinical: Cancer & lymph nodes
- Cervical sentinel nodes (deep cervical nodes) may be involved in spread of cancer fr
thorax & abdomen
- Radical neck dissection performed when cancer invades cervical lymphatics. Carotid
arteries & vagus nerve are preserved but IJV removed
NIGEL FONG 2011/2012
PAGE A266
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
4. CRANIUM
!
A. THE SKULL: EXTERNAL VIEW
!
Overview
•
Neurocranium:
-
•
8 bones: 1 Frontal, 2 parietal, 1 occipital, 2 temporal, 1 sphenoid & 1 ethmoid
Divided into the vault/calvaria (upper part) and base (lower part)
Bones dvp through intramembranous ossification, and are made up of made up of
ext & int tables (compact bone) separated by diploe (spongy bone)
Viscerocranium (facial skeleton):
-
15 bones: 2 maxillae, 1 mandible, 2 zygomatic, 2 nasal, 2 lacrimal, 1 vomer, 2
palatine, 2 inf conchae.
Mandible united to skull by tempromandibular joint
Visceral openings:
•
•
•
•
Orbital margins: [sup] frontal, [lat] zygomatic, [inf] maxilla [med] maxilla & frontal
Jaws: Maxillae form upper jaw & ant hard palate, Mandible forms lower jaw.
Nose: nasal bones form bridge, maxilla forms lower border, vomer forms nasal septum
- Opens internally as the chonae (pos nasal aperture), bounded laterally by the med
pterygoid plates of sphenoid
Ear:
- Ext auditory (acoustic) meatus: tympanic plate of temporal bone
-
Int auditory (acoustic) meatus & cartilaginous part of auditory tube: pierces
pos surface of petrous part of temporal bone
NIGEL FONG 2011/2012
PAGE A267
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
External landmarks
•
Sutures:
- Coronal: Btw parietal & frontal bones
-
•
•
•
•
Sagittal: Btw contralateral parietal bones
Lambdoid: Btw parietal & occipital bones
Occipital condyles articulate with the atlas (C1): see back
Zygomatic bone forms prominence of cheek.
Ext occipital protuberance is easily palpable; sup nuchal lines extend lat fr this.
Pterion: where ant/inf corner of parietal bone articulates w greater wing of sphenoid,
one finger pos to frontal process of zygomatic, 2 finger sup to zygomatic arch.
- Overlies ant div of middle meningeal arteries
- Thinnest part, fractures lead to extradural hemorrhage (see middle meningeal art)
!
NIGEL FONG 2011/2012
PAGE A268
M1 NOTES IN GROSS ANATOMY
!
Sphenoid: pos view
8 | BRAIN, HEAD & NECK
!
!
!
Clinical notes
•
•
Fractures:
- Depressed fractures of the calvaria (skull cap) may compress and injure the brain
- Fractures of nasal bone most common
- When the meninges tear, blood & CSF may leak out through visceral openings
(which opening depends on leaking from which cranial fossa – see later)
Adult pericranium has poor osteogenic properties and regenerates poorly: after surgery,
bone flaps have to be put back and wired.
!
NIGEL FONG 2011/2012
PAGE A269
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Neonatal skull
•
•
•
•
•
Skull bones (calvaria) of infant are soft and loosely connected, without diploe
- Enables shape change during passage thru the birth canal, and facilitating growth
- Premature closure of sutures (primary craniosynostosis) results in malformations
(but normally does not affect brain development)
Fontanelle (unossified membranous intervals):
- Ant fontanelle: diamond/star shape at site of future bregma, bounded by sep
halves of frontal bone & parietal bone
- Pos fontanelle: triangle shape at site of future lambda, bounded by parietal bones
& occipital bone
Frontal bone and mandible dvp from 2 halves which later fuse, obliterating sutures.
- Persistent frontal suture must not be interpreted as fracture
Mandible elongates to assume adult shape after eruption of permanent teeth.
- In old age, when teeth are lost, size of mandible is reduced
Development of temporal bone:
- No mastoid processes and smaller tympanic part at birth:
- Tympanic mem closer to surface
- CN VII close to surface when they emerge fr stylomastoid foramina and are easily
injured (e.g. by forceps delivery)
B. CRANIAL CAVITY: INTERNAL VIEW
Cranial fossae
•
!
Ant cranial fossa contain frontal lobes
-
•
Formed by orbital plates of frontal bone, cribiform plate of ethmoid, up to lesser
wing of sphenoid
Middle cranial fossa contain temporal lobes
-
•
Median part: hypophysial fossa (sella turcica) containing pituitary gland forms in
the body of the sphenoid bone. Bounded [ant] tuberculum sellae, [pos] dorsum sellae
Lateral part: formed by greater wings of sphenoid & sup border of petrous (“rock”,
hardest) part of temporal bone
Optic canal & orbital fissure communicates with orbit
Posterior cranial fossa: contain hindbrain (cerebellum, pons, medulla oblongata)
-
Formed by occipital bone & mastoid part of temporal bone
Foramen magnum transmits medulla oblongata & meninges; through this, spinal
cord is continuous with brain
Note sinuses – see venous drainage of brain.
NIGEL FONG 2011/2012
PAGE A270
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Foramina of cranial fossae
•
•
•
•
See diagram
Nerves of the middle cranial fossa may take a short course between the bone and dura;
location of fossae may not be where the nerves leave the brain.
Identification: Large CN II is assoc w ICA, large CN V emerges under tentorium
cerebelli. CN IX, X, XI travel through jugular foramen lat to jugular tubercle.
Int carotid artery (and accompanying sympathetic plexus) passes horizontally across
the area of the foramen lacerum (through cavernous sinus). Foramen lacerum is closed
by cartilage.
Inf relations of cranial fossae
•
Fractures, bleeds, or CSF leakage from the cranial fossae may come out from
- Ant: nose, orbit (e.g. bilateral bruised eye indicates ant fossa bleed)
- Middle: into pharynx and is then swallowed (appears as GIT bleed), or ears.
- Pos: Bruise appears at the back of the neck
NIGEL FONG 2011/2012
PAGE A271
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
C. MENINGES & VENOUS DRAINAGE OF BRAIN
!
Dura mater
•
Endosteal layer: periosteum of bone
-
•
•
!
Continuous with sutural ligaments and periosteum on outside of skull
does not extend through foramen magnum to dura of spinal cord
Meningeal layer: dense strong
fibrous layer
- Continuous with spinal dura
through foramen magnum
- Continuous with epineurum of
cranial nerves, ensheaths cranial
nerves as they pass through
foramina of skull
Septa formed by meningeal layer
resist rotatory displacemt of brain
!
SEPTA
DESCRIPTION
ANT ATTACH
Falx
cerebelli
Sickle-shape midline
fold partially sep.
cerebral hemispheres
Int frontal
crest, crista
galli (ethmoid)
Tentorium
cerebelli
Crescent-shaped roof
over pos cranial fossa
Sep cerebellum fr
occipital lobes
Diaphragma
sellae
Small circular roof
for hypophysial fossa
Clinoid proc of
sphenoid,
petrous part of
temporal bone
POS ATTACH
Int occipital
protuberance,
tentorium
Falx attaches to
and holds
tentorium up
Int surf occipital
Btw clinoid proc
OPENING
Corpus callosum
connecting R/L
hemispheres
Tentorial notch:
midbrain passes
through
Pituitary stalk,
hypophyseal cap.
Arachnoid & Pia mater (leptomeninges)
•
•
Arachnoid mater: Delicate impermeable membrane deep to dura, holds CSF to
cushion brain and protect against impacts
- Held against dura by pressure of CSF, held to pia by arachnoid trabeculae.
- Project into dural venous sinuses = arachnoid villi / granulations (see CSF)
Pia mater: Adheres to surface of brain, follows all its contours
-
Fuses with epineurum of cranial nerves (except CN II, which is surrounded by all
meninges)
NIGEL FONG 2011/2012
PAGE A272
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Spaces in the meninges
•
Epidural (extradural) space: potential space btw periosteal layer of dura & cranium
-
•
•
•
Not continuous with normal spinal epidural space which is extra-periosteal while
the epidural space is intra-periosteal
- Meningeal arteries travel in periosteal layer of dura
Dural venous sinuses: normal space between the 2 layers of dura
Subdural space: potential space btw dura & arachnoid
Subarachnoid space: normal space btw arachnoid & pia
-
Contain CSF, arteries of the circle of Willis, etc
Nerve supply of the dura
•
•
Dura innervated by meningeal branches from CN V1, V2, V3, X, C2-3
Clinical: Dural headaches – dura is sensitive to pain even though brain itself is not
-
EG distension of scalp or meningeal vessels
Following lumbar puncture, brain sags slightly, pulling on dura, causing headache
Meningeal arteries
•
•
•
•
Lie in periosteal layer of dura, supply dura and calvaria
- Accompanied by meningeal v
Largest branch: middle meningeal artery
- Enters middle cranial fossa through foramen spinosum, runs laterally
- Divides into ant & pos branches on greater wing of sphenoid
- Ant branch runs superiorly across the pterion
Accompanied by meningeal veins:
- Middle meningeal veins drain into pterygoid plexus (outside the cranium)
Clinical: Fracture of pterion can rupture the middle meningeal artery, resulting in
extradural hemorrhage
!
!
!
NIGEL FONG 2011/2012
PAGE A273
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Cranial hemorrhage
•
Compression of brain compromises perfusion; this causes the neurological signs seen
Extradural
Subdural
Subarachnoid
Btw bone & periosteum
Btw dura & arachnoid
Btw arachnoid & pia
SOURCE
Torn middle meningeal art
Tearing of sup cerebral veins
Arterial: ruptured aneurysm
CAUSE
Trauma, skull fracture etc
(esp to pterion)
Minor blow esp in elderly, w
A/P displacement (lateral
mvmt prevented by falx)
Congenital, angioma, etc
SYMP
Brief concussion, period of
lucidity, rapid decline
Decline normally slower
Severe headache, stiff neck
On lumbar puncture, blood
seen (circulation of CSF)
RADIO
Lens shaped
Crescent shape, does not
cross midline (falx)
Can see sulci of brain
TYPE
!
!
NIGEL FONG 2011/2012
PAGE A274
M1 NOTES IN GROSS ANATOMY
D. VENOUS SINUSES OF BRAIN
8 | BRAIN, HEAD & NECK
!
!
!
Dural venous sinuses
•
Endothelium-lined valveless spaces btw periosteal & meningeal layers of dura
- Receive emissary veins passing fr outside cranial cavity (e.g. scalp) into sinuses.
Normally bloodflow is away from the brain, but they are valveless and infections
may enter the cranial cavity through these means
•
Sup sagittal sinus runs bwd in
upper border of falx.
- Receiving sup cerebral veins,
cont w venous lacunae
•
•
•
•
•
•
Inf sagittal sinus runs in inf concave
border of falx cerebelli
Union of inf sagittal sinus & great cerebral
vein (of Galen) forms the straight sinus,
which runs in junc of falx & tentorium
Confluence of sinuses: meeting pt of sup sagittal, straight, occipital, transverse sinus
Transverse sinus: Drains blood fr confluence of sinus, via lat margin of tentorium
Sigmoid sinus: Cont. of transverse sinus, following S-shaped course in grooves in pos
cranial fossa, leaving skull through foramen to become int jugular vein.
Occipital sinus: runs superiorly in attached pos border of falx cerebelli, from
communication w int vertebral plexus, to confluence of sinus
Cavernous sinus
•
•
Cavernous sinus lies on lat side of body of sphenoid, btw endosteal & meningeal
layers of dura
- Receives inf ophthalmic vein & central vein of retina
- L & R cavernous sinuses communicate through intercavernous sinuses ant/pos to
pituitary stalk
Petrosal sinuses: drain cavernous sinuses
-
•
Sup petrosal sinus: fr cavernous sinus, via anterolat margin of tentorium, to
transverse sinus
- Inf petrosal sinuses: fr cavernous sinus to junction of sigmoid sinus & int jugular v
Basilar sinuses connect inf petrosal sinuses to each other and to vertebral plexus.
•
•
Communicates with pterygoid plexus
Clinical: see spread of infection from face
!
NIGEL FONG 2011/2012
PAGE A275
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Structures & relations of cavernous sinus
•
•
Structures inside cavernous sinus:
- Thru sinus: ICA, sympathetic plexus, CN VI
In lat wall: CN III, IV, V1 & V2
Relations of cavernous sinus & pituitary
- Ant: Sup orbital fissure
- Lat: Foramen rotundum, ovale, trigeminal ganglion
- Pos: Foramen lacerum
- Sup: Optic chiasm
- Med: Pituitary gland (in sella turnica)
- Inf: Nasal cavity, sphenoid sinus
- Clinical: Hence pituitary tumors may compress the
optic chiasm
!
NIGEL FONG 2011/2012
!
PAGE A276
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
5. BRAIN
!
A. STRUCTURE OF THE BRAIN
!
Embryology
•
•
Brain develops from cephalic part of neural tube (eye develops as outgrowth of brain)
Centre of neural tube later gives rise to ventricles of the brain.
PRIMARY VESICLES
Prosencephalon (forebrain)
Mesencephalon (midbrain)
Rhombencephalon (hindbrain)
SECONDARY VESICLES
DERIVATIVE
Telencephalon
Cerebral cortex, Corpus striatum
Diencephalon
Thalamus & Hypothalamus
Midbrain
Midbrain
Metencephalon
Pons & Cerebellum
Myelencephalon
Medulla oblongata
!
Lobes of the cerebrum
•
•
Med
Cortex (grey matter, cell bodies) located on outside, white matter (axons) on inside
- Cortex made up of gyri (gyrus, ridges), separated by sulci (sulcus, creases)
4 surface lobes of the brain (frontal, parietal, temporal, occipital)
-
•
Lat
L/R separated by falx cerebrelli
Central sulcus divides frontal & parietal lobe
Lateral sulcus divides temporal lobe & parietal lobe
Parieto-occipital sulcus (view on medial aspect) div parietal & occipital lobe.
- Calcarine sulcus further subdivides the occipital lobe
Limbic lobe surrounds medial margin of hemisphere
-
Limbic sys (hippocampus, fornix, amygdala, etc) – impt in emotion, behaviour, etc
NIGEL FONG 2011/2012
PAGE A277
M1 NOTES IN GROSS ANATOMY
Corpus callosum
•
•
8 | BRAIN, HEAD & NECK
!!!!!!
!
White matter connecting two hemispheres
- Consists of body, splenium (pos), genu (ant), rostrum (inf, to ant comissure)
Ant & pos commissures on either side of the corpus callosum
NIGEL FONG 2011/2012
PAGE A278
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
!
Diencephalon region
•
Thalamus: Relay station for relay of sensation to cerebral cortex (all sensory neurons
reaching cortex pass through thalamus, except CN I)
- Most medial, on either side of 3rd ventricle.
Hypothalamus: major survival systems – reproduction, growth & metabolism, food &
water intake, temperature control, pituitary output etc.
- Lateral wall & floor of 3rd ventricle
Internal capsule (forms corona radiata) separates thalamus from lentiform nucleus
•
- Horiz view: ant limb, genu, pos limb, retrolentiform part
- Contains fibres running btw cortex & thalamus, brainstem, spinal cord
- Corticospinal (pyramidal) tract descends in pos limb
Basal ganglia: gray matter located near base of hemisphere
•
•
-
Lentiform nucleus: putamen & globus pallidus (pallidum)
Caudate nucleus: on upper surf of thalamus (corpus striatum refers to caudate
nucleus and putamen)
- Also inc. subthalmic nucleus in diencephalon and substantia nigra in midbrain.
Fornix: ‘tail’ left behind as hippocampus migrates from above corpus callosum to the
temporal lobes
- Comprises: Crus (enters fr hippocampus), Body (beneath corpus callosum),
Pillars/columns (leave for diencephalon)
rd
3 ventricle (see later) lies in this region
-
•
•
-
Roof: fornix | Lat: thalamus & hypothalamus | Pos: Pineal gland | Floor:
infundibulum, mammillary bodies
NIGEL FONG 2011/2012
PAGE A279
M1 NOTES IN GROSS ANATOMY
Brainstem
8 | BRAIN, HEAD & NECK
Ant view
!
Pos view
•
Midbrain: 2 large cerebral peduncles bordering interpeduncular fossa
•
- Dorsum (roof): cerebral peduncles
- Sup colliculi (visual system) & inf colliculi (auditory system)
Pons: lies on top of clivus, transverse fibres raise surface ridges
•
•
•
!
Medulla oblongata:
- Pyramids besides ant median fissure & pyramidal decussation (spinothalamic tract)
- Pos: Gracile tubercles & cuneate tubercles (dorsal column medial lemniscus tract)
4th ventricle (diamond shaped marking) lies behind pons & upper medulla, aqueduct
of Sylvius lies in the midbrain
Function
- Cranial nerves emerge from brainstem nuclei (except CN I & II): see cranial nerves
- Ascending and descending tracts pass through brainstem
- Midbrain also has centers for visual & auditory reflex, motor function, transmission
of pain, visceral functions.
- Medulla nuclei regulate visceral functions (inc respiration & heart rate)
Cerebellum
•
•
•
Motor function: coordinate activity of muscle groups
2 hemispheres connected by vermis
- Hemispheres show fissures, with folia in between
6 cerebellar peduncles connect cerebellum to dorsal side of brainstem
- Sup peduncles connect to midbrain, middle to pons, inf to medulla
Ant view:
NIGEL FONG 2011/2012
Lat view:
PAGE A280
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
B. VENTRICLES & CIRCULATION OF CSF
!
Ventricular system
!
!!!!!
!
•
2 lateral ventricles in the cenrebral hemispheres
•
- Body (parietal lobe), and ant (frontal), post (occipital) & inf (temporal) horns
- Opens through interventricular foramen into 3rd ventricle
3rd ventricle: slit-like cavity btw R & L diencephalon
-
•
Drains via (cerebral) aqueduct of Sylvius to 4th ventricle
4th ventricle: in pos pons & medulla, extending inferoposteriorly
-
Continuous with central canal of spinal cord
Circulation of CSF
•
•
•
•
•
CSF secreted by choroid plexuses in each ventricle (vascular pia mater covered by
cuboidal epithelium)
Leaves lateral ventricles through interventricular foramina, entering 3rd ventricle, and
then passing through the aqueduct of Sylvius to the 4th ventricle
Enters subarachnoid space via:
- Paired lateral foramen of Luschka
- Single midline foramen of Magendie
Reabsorbed into venous system via arachnoid granulations
- Protrude through meningeal layer of dura into dural venous sinuses)
- Usu. at sup sagittal, transverse, and other dural venous sinuses
CSF continuous with subarachnoid cisterns, central canal of spinal cord, extensions
surrounding optic nerve
Hydrocephalus
•
•
•
Intra-cranial pressure depends on the balance between CSF secretion & reabsorption.
Hydrocephalus = abnormal accumulation of CSF in ventricles of brain, due to:
- Blockage of CSF outflow, usually in cerebral aqueduct (e.g. tumor, infection)
- Interference with absorption (e.g. blocked arachnoid granulations aft hemorrhage)
- Overproduction of CSF
Hydrocephalus results in ventricle dilation & increased intra-cranial pressure
- Squeeze brain btw ventricular fluid & calvarial bones.
- In infants: brain & calvaria expand because sutures &fontanelles still open
NIGEL FONG 2011/2012
PAGE A281
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
C. THE CEREBRAL CORTEX
Organization of cerebral cortex
•
•
•
Laminar organization: layered by cell types from surface to deep
Columnar organization: Columns (∼200 neurons each) form functional units
Connections btw columns
- Short association fibres : connect adjacent ipsilat gyri (S/M pyramidal neuron)
- Long association fibres : connect different cortical regions within hemisphere
- Comissural fibres
: corpus callosum btw homologous reg of 2 hemispheres.
- Projection fibres
: to brainstem, spinal cord.
: corticopedal (input) or corticofugal (output)
: cholinergic / aminergic afferents implicated in psychiatry.
Neuron types
•
Pyramidal (w v long dendrite) - Primary excitatory cell type, uses glutamate
-
•
All efferent axons from cerebral cortex are pyramidal and excitatory
Size of pyramidal cell determines distance projected: small/medium project to
ipsilateral cortex, large project further.
Non-pyramidal
- Mostly inhibitory, use GABA
•
Supporting glial cells: astrocytes, oligodendrocytes, microglia (see histology)
Brodmann’s map
Somatic sensory & motor
•
Principle: a primary area responds to simple features and adjacent areas interprete
AREA
LOCATION
FUNCTION
STIMULATION
DAMAGE
1º somatosensory
3, 1, 2: Post-central
gyrus, parietal lobe
Receives somatic
sensation from
contralateral body
Contralateral
parasthesia &
numbness
Contralateral loss
of sensation
SomSens
association
5: pos parietal lobe
Moving arms twds
obj, obj manipulation
1º motor
4: Pre-central gyrus,
frontal lobe
Upper motor neurons
for contralateral body
Single contralat
muscle moves
See UMN lesion:
affects contralat
2º motor
6 lat: Premotor cortex
6 med: Supplementary
motor area
Complex movements,
planning, steady nonmoving joints etc
NIGEL FONG 2011/2012
Postural instabil
Akinesia: X
initiate mvmt
PAGE A282
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Homunculus & plasticity
•
•
Sensory & motor homunculus show the body areas which the cortex maps too: legs
medial and upper body lateral
- Area of representation disproportionate: highly sensitive / finely controlled areas
(fingers, face) are better represented
Plasticity: sensory & motor maps can be modified by peripheral events
- Initial paralysis with nerve damage / infarct may be followed by progressive
recovery within days as other cell columns close to lesion take on missing function
Vision
•
•
Visual info reaches 1º visual cortex, then visual association cortex for processing
‘’What’ and ‘Where’ processed differently: the greater the complexity processed, the
greater the distance from the 1º visual cortex
‘Where’ pathway:
‘What’ pathway:
!
AREA
LOCATION
FUNCTION
STIMULATION
DAMAGE
1º visual
17: Occipital lobe, both
banks of calcarine sulcus
Simple visual info fr
contralat vis field
Crude flashes of
bright light
Loss of vision in
contralat vis field
Visual
assoc
18, 19: Occipital lobe,
adjacent to 1º vis cortex
More complex visual
processing
Hallucination of
formed images
Visual agnosia:
✓ see ✗ recognize
Where
pathway
Dorsal visual pathway:
go up pos parietal lobe
Process spatial rls,
motion info
-
-
What
pathway
Ventral visual pathway:
underside of temporal l
Process colour/form
info, recognition
-
-
Frontal
eye field
Middle frontal gyrus in
area 4
Voluntary eye mvmt
(saccade) to contralat
Both eyes deviate
contralaterally
Both eyes deviate
ipsilaterally
NIGEL FONG 2011/2012
PAGE A283
M1 NOTES IN GROSS ANATOMY
!
!
Hearing & speech
AREA
LOCATION
FUNCTION
1º auditory
41, 21, 22: Sup temporal
gyrus
Auditory info from
both ears
Wernicke’s
speech area
[Auditory assoc. cortex]
22: sup temporal gyrus
Comprehension of
spoken word
Broca’s
speech area
44, 45: Inf frontal gyrus
Speech production
•
Tinnitus:
buzzing,
ringing in ear
Inhibition of
speech, utter
vowel sounds
DAMAGE
Minor: each ear rep
bilaterally
Receptive aphasia:
✓hear ✗understand
Speech ✗meaningful
Expressive aphasia:
✓understand
✗express language
Normal func require both Wernicke’s & Broca’s areas
- Conn. by long association fibres of arcuate fasciculus
- Speech functions mostly on dominant hemisphere
Presentation of speech lesions
- Wernicke’s [Receptive aphasia]: speech fluent but
unintelligible and patient doesn’t realise it
- Broca’s [Expressive aphasia]: speech slow, laboured
!
Special sensation [not important]
•
•
•
!
STIMULATION
Aphasia (disturbed language function)
•
!
8 | BRAIN, HEAD & NECK
1º vestibular cortex for appreciation of spatial orientation (stimulation: vertigo)
1º gustatory cortex for taste (damage: loss of taste on contralateral side)
1º olfactory cortex for smell in inf temporal lobe (damage: ansomnia)
Multimodal association areas
•
•
Pos multimodal assoc: parietotemporal reg, supramarginal & angular gyri (7, 39, 40)
- Multisensory perception including visual/spatial, language, attention
Ant multimodal assoc area: prefrontal cortex
- Affective behaviour & judgement: working memory, planning, language production
- Damage: behaviour/personality change, with no appreciation of social norm
Hemispherical dominance
•
•
•
Both cerebral hemispheres are asymmetrical in certain respects
- Most R-handers are L-hemisphere dominant, L-handers can be either or both.
Dominant hemisphere = language dominance
- Non-dom hemisphere helps to appreciate spatial dimensions, store tone memories
EG damage to pos multimodal association area
- Dominant hemisphere (Gerstmann syn): Alexia (cannot read), agraphia (cannot
write), expressive aphasia, acalculia, agnosia (cannot recognize perceptions)
- Non-dominant hemisphere: hemineglect syndrome (neglect of contralateral side)
!
NIGEL FONG 2011/2012
PAGE A284
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
D. BLOOD SUPPLY OF THE BRAIN
Overview
!
•
•
Brain is only 2.5% of body weight but uses 20% of oxygen at rest.
Internal carotid sys (ant circulation): 80% of cerebral blood flow
- Int carotid gives ant cerebral arteries & continues as middle cerebral arteries
•
Vertebrobasilar sys (pos circulation): 20% of cerebral blood flow, also SS hindbrain
- Vertebral arteries: fr subclavian, ascend in transverse foramen of C1-6 vertebrae
-
Merge at pontomedullary junct to form basilar artery
-
Basilar art runs along ant midline of pons, until its rostral border
Basilar art bifurcates and continues as pos cerebral arteries
-
Clinical: Subclavian steal syndrome – increased upper limb usage allows less
blood to flow into vertebral art, causing fainting
Circle of Willis
•
•
•
Circle of Willis (cerebral arterial circle) on
ventral surface of brain, in subarachnoid space
- Impt anastomosis but X protect against
sudden occlusion as comm arteries are small
Ant to pos: ant communicating artery, ant
cerebral art, int carotid art, pos communicating
art, pos cerebral art
Clinical: Berry aneurysms tend to arise at
bifurcations within the circle. Rupture causes
subarachnoid hemorrhage.
!
!
NIGEL FONG 2011/2012
REG
Vertebrobasilar
MODE
Angiogram
COND
Berry aneurysm
VIS
As shown
NOTE
Injection of contrast
into either vertebral
artery shows up on
both sides of brain as
they merge to form
basilar
PAGE A285
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Proximal branches
•
Fr int carotid
•
Fr vertebrobasilar
- Hypophysial art to infundibulum, giving pituitary portal sys
- Opthalmic art to orbit, SS eye, part of nose, sinuses
- Labyrinthine art (fr basilar) to inner ear
- 1 ant & 2 pos spinal art (fr vertebral art) – see spine
!
Supply of hindbrain
•
Supply of cerebellum & adjacent structures (fr vertebrobasilar system)
- Pos inf cerebellar : also SS lat medulla, inf vermis, 4th ventricle choroid plexus
-
•
Ant inf cerebellar : also SS part of pons (cochlear nuclei)
Sup cerebellar
: also SS pons, sup cerebellar peduncle, tectum of midbrain
Pontine arteries: multiple short branches fr basilar art to the pons
!
!
Supply of cerebral cortex
•
•
•
Course of cerebral arteries:
- Ant cerebral art
: loop around (sup to) optic chiasm to med surface
: forms arch around genu of corpus callosum (ID key)
- Middle cerebral art : pass along lat fissure, split into upper/lower branches
- Pos cerebral art
: winds around midbrain
Medial surf: mainly ant & pos cerebral art, territory divided by parieto-occipital sulcus
Lateral surf: mainly middle cerebral art, except for thin strip on sup (ant) & inf (pos)
REG
R internal carotid
MODE
Angiogram
COND
Normal
VIS
As shown
NOTE
NIGEL FONG 2011/2012
PAGE A286
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
Supply of deep structures of brain
•
•
!
Deep structures (thalamus, internal capsule, corpus striatum, choroid plexus etc)
- Lat striate art fr middle cerebral art
- Medial striate art (recurrent art of Heubner) fr ant cerebral art
- Ant choroidal art fr int carotid art
- Pos choroidal art / penetrating branches fr pos cerebral art
Occlusion to lat striate arteries is a cause of classic stroke:
- Severe ramifications as int capsule contains impt ascending & descending fibres
- Disruption to descending upper motor neurons of corticospinal tract causes
hemiplegia (paralysis of contralateral part of body)
Blood-brain barrier
•
•
•
BBB isolates brain from blood, neurons are instead bathed in the stable & chemically
optimal environment of CSF
- Exception: BBB is leaky at the hypothalamus, allowing hypothalamus to sense level
of circulating hormones
BBB is due to tight junctions btw endothelial cells (induced by astrocytic end feet)
- Glucose actively transported into CSF by astrocytes
- Water soluble substances blocked (e.g. plasma proteins, macromolecules)
- Lipid soluble substances cross
- Implications for drug use: e.g. antibiotics, chemo agents etc
BBB can break down when
- Hypertension: when BP > power of arterioles to control, causing cerebral edema
- Infection: perhaps due to leukocyte migration
- Osmotic challenge (sometimes on purpose)
- Severe hypercapnia: due to arteriolar muscle relaxation
!
!
!
!
!
NIGEL FONG 2011/2012
PAGE A287
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
E. SUMMARY: CRANIAL NERVES [see separate sections for each nerve]
•
•
•
Special sensory: CN I, II, VIII
Motor: CN III, IV, VI, XI (spinal root), XII
Mixed: CN V, VII, IX, X (nerves of pharyngeal arches – see embryology)
Special & Visceral Sensory
•
•
*Smell is the only sensation that does not pass through thalamus
CNS nuclei are organized by function
!
CRANIAL N
FIBRE
SUPPLY
1º NEURON
2º NEURON
I
Olfactory
Spec Sen
Smell
Olfac epithelium
*
II
Optic
Spec Sen
Vision: Retina
Retina ganglion
cells
Thalamus: lat
geniculate nuc
VIII
Vestibulocochlear
Spec Sen
Vestibular sense, balance
Vestibular gang.
Vestibular nuc
Hearing: spiral organ
Spiral gang
Cochlear nuc
VII
Facial
Spec Sen
Taste: Ant 2/3 of tongue
Geniculate gang.
IX
Glossopharyngeal
Spec Sen
Taste: Pos 1/3 of tongue
Vis Sen
Baroreception: carotid sinus
Glossopharyngeal
ganglion (inf)
Spec Sen
Taste: Palate, epiglottis
Vis Sen
Heart, Resp, Pharynx,
Larynx, GIT up to midgut
X
Vagus
Vagal ganglion
(inf)
Nucleus tractus
solitarius
!
Somatic Sensory
•
Note that the ear receives multiple supply from CN V, VII, IX, X, C2-3
!
CRANIAL N
V
V1
V2
V3
Trigeminal
Opthalmic
Maxillary
Mandibular
FIBRE
SUPPLY
1º NEURON
2º NEURON
Som Sen
Face, ant to vertex ear chin
- Cornea, forehead & scalp
- Cheek, upper jaw
- Chin, lower jaw, ant 1/3
tongue
Trigeminal
ganglion
Dpd on modality:
Principal sens nc
Mesencephalic nc
Spinal nuc of V
VII
Facial
Som Sen
Ext ear (via intemediate n)
Geniculate gang.
IX
Glossopharyngeal
Som Sen
Pos 1/3 tongue, Pharynx,
Ext & middle ear
Glossopharyngeal
ganglion (sup)
X
Vagus
Som Sen
Ext ear, Larynx
Vagal gang. (sup)
Visceral Motor (Parasympathetic)
Spinal nuc of V
!
CRANIAL N
FIBRE
SUPPLY
1º NEURON
2º NEURON
III
Oculomotor
Parasym
Sphincter pupillae, ciliary
muscle
EdingerWestphal nuc.
Ciliary ganglion
VII
Facial
Parasym
Lacrimal gland
Lacrimal nuc
Pterygopalatine
Parasym
Submandibular, sublingual
IX
Glos-phary
Parasym
Parotid gland
X
Vagus
Parasym
CVS, Resp, GIT up to
midgut
NIGEL FONG 2011/2012
Salivatory nuc
Dorsal motor nuc
Submandibular g
Otic ganglion
Various
PAGE A288
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Somatic Motor
•
Cortico-bulbar (-nuclear) tract: UMN fr cerebral cortex, synapse on cranial n (LMN)
•
CNs generally receive bilateral UMN influence (from both L/R motor cortex)
- Exception: Facial nerve fibres to lower face only receive contralateral UMN input
- Exception: CN XII receives bilateral input but contralateral is dominant
- Clinical: Lesion of brain UMN not significally seen, except in lower face & tongue
!
CRANIAL N
FIBRE
SUPPLY
1º NEURON
III
Oculomotor
Som Mot
Extraoccular musc except
sup oblique & lat rectus
Oculomotor nuc
IV
Trochlear
Som Mot
Sup oblique muscle
Trochlear nuc
VI
Abducens
Som Mot
Lat rectus muscle
Abducens nuc
V
Trigeminal
Mandibular
Som Mot
Mus of mastication, tensors
tympani, palatini, digastric
(ant belly), mylohyoid
Trigeminal motor
nuc
VII
Facial
Som Mot
Musc of facial expression,
stapedius, stylohyoid,
digastric (pos belly)
Facial motor nuc
IX
Glossopharyngeal
Som Mot
Stylopharyngeus
Nucleus
Ambiguus
V3
X
Vagus
Som Mot
Musc of soft palate (exc
tensor palatini), pharynx
(exc stylopharyngeus),
larynx, sup 2/3 esophagus
XI
(Spinal)
Accessory
Som Mot
Sternocleidomastoid,
trapezius
Spinal accessory
nuc (in sp cord)
XII
Hypoglossal
Som Mot
Musc of tongue (intrinsic,
extrinsic) exc palatoglossus
Hypoglossal nuc.
2º NEURON
Somatic motor
LMNs
No post-synaptic
neuron, unlike
visceral motor
[See embryology:
pharyngeal arch]
!
Location of CN nuclei
•
Brainstem nuclei are arranged in functional columns. General principle (see exceptions)
-
Forebrain
Midbrain
Pons
Medulla
Cervical spinal cord
I, II
III, IV
V – VIII
IX, X, XII
XI
Nuclei serving many n extend further (e.g. spinal nuc of V - fr pons to upp sp cord
!
NIGEL FONG 2011/2012
PAGE A289
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Exit/entry of cranial nerves from brain
•
•
•
•
•
•
•
•
•
•
All emerge anteriorly from brainstem, except CN IV
CN I
: Olfactory bulb travels into temporal lobe
CN II
: Optic chiasm travels into thalamus (lat geniculate nuc)
CN III
: Emerge fr medial surface, cerebral peduncle (midbrain)
CN IV
: Emerge fr dorsal brainstem, winding around peduncle
CN V
: Emerge fr pons
CN VI – VII
: Emerge fr pontomedullary junction
CN IX, X
: Emerge fr lat part of medulla
CN XI
: From cervical spinal cord, ascend up foramen magnum
CN XII
: Emerge fr med part of medulla
!
!
!
NIGEL FONG 2011/2012
PAGE A290
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
F. CEREBELLUM
!
Gross anatomy
•
Divided into ant, pos, flocculonodular lobes by primary and posterolat fissures
•
•
Cerebellar cortex receive afferents, efferents originate from deep cerebellar nuclei
Connected to brainstem via cerebellar peduncles (axon bundles)
Principles
•
•
•
Receives & integrates balance sense, prioceptive
information, motor intention
Unconsciously controls motor function: postural
equilibrium, motor activity, tonus.
Cerebellum is concerned with same side of body
- R cerebral cortex controls L body. Hence to
control L body, cerebrocerebllum must receive
input from contralat i.e. R cerebral cortex
!
!
DIVISION
Vestibulocerebellum
Spinocerebellum
Cerebrocerebellum
(Pontocerebellum)
LOCATION
Flocculonodular lobe
Vermis & adjacent part
Lateral parts
AFFERENTS
Balance sense:
Ipsilat vestibular nuclei
Unconscious proprioception:
Ipsilat spinocerebellar tract
(uncrossed pathway)
Motor intention:
Contralateral cerebral
cortex
EFFERENTS
Ipsilat vestibular nuc, then to:
Vestibular nuclei, then to
ipsilat motor UMN
Thalamus first, then
contralat cerebral
cortex
Adjusts ongoing movement,
allows smooth mvmt
Coordinates planning
of limb movements
FUNCTION
• Vestibulospinal tract:
ipsilat postural muscles
• CN III, IV, VI nuclei
Postural equilibrium
Vestibulo-ocular reflex
Cerebellar dysfunction
•
Presents ipsilaterally as incoordination of limb movements
•
•
•
Dysequilibrium: unsteady in standing position, tends to fall to side of lesion
Dystonia: loss in resistance normally offered by muscles to passive manipulation
Dyssynergia: loss of coordinated muscle movement, presenting as cerebellar signs
- Past pointing: hand cannot stop moving at desired point
- Intention tremor: quiver due to faulty agonist/antagonist synergies
- Dysdiadochokinesia: inability to perform rapid pronation/supination etc
NIGEL FONG 2011/2012
PAGE A291
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
6. ORBIT & EYE
!
A. BOUNDARIES
!
!
!
Bony walls of the orbit
•
•
•
•
•
•
Pyramidal cavity with bases directed ant/lat and apices pos/med.
- Medial walls parallel, lateral walls perpendicular, so axes of orbits diverge at 45º
- Eyeball is much smaller than its cavity
- Periorbita (periosteum of orbit) cont. w pericranium, periosteal layer of dura…
Roof
: Frontal bone (sep orbit fr ant cranial fossa & frontal lobe of brain)
Lat wall : Zygomatic bone, greater wing of sphenoid
Med wall : Maxilla, Lacrimal bone, Ethmoid (sep orbit fr ethmoidal sinus)
Floor
: Maxilla (sep orbit fr maxillary sinus)
Clinical: The walls of the orbit (esp med) are thin, blowout fractures of orbit may
involve ethmoidal/sphenoidal sinus (medial), maxillary sinus (inf), or frontal lobe (sup)
Openings into the orbit
•
Optic canal: in lesser wing of sphenoid, communicates with middle cranial fossa
•
- Optic n (CN II) with ctrl retinal artery, opthalmic artery (fr int carotid)
Sup orbital fissure: btw greater & lesser wings of sphenoid, to middle cranial fossa
•
- CN III, IV, VI, br of CN V1 (frontal, lacrimal, nasocilary), sup opthalmic vein
Inf orbital fissure: btw maxilla & greater wing of sphenoid, to pterygopalatine fossa
•
•
•
- CN V2, inf opthalmic vein, sympathetic nerves
Supra-orbital notch/foramen: supraorbital nerve (fr CN V1) & vessels
Infraorbital foramen / canal: infraorbital nerve (fr CN V2) & vessels
Nasolacrimal canal: Nasolacrimal duct
Eyelids
•
•
•
•
Sup & inf eyelids meet at med/lat palpebral commissures (with med/lat palpebral lig)
- Function: protect eyeball fr injury & excessive light
- Fibrous support prov by orbital septum (attached to periosteum) & Sup/inf tarsus
- Eyelashes at margin of lids to minimize entry of foreign objects
Layers sup – deep: skin & subcutaneous tissue, orbicularis occuli muscle, orbital
septum, tarsus, conjunctiva
To open / look up: levator palpebrae superioris (CN III) & sup tarsal muscle
(smooth muscle w sympathetic supply, sometimes considered part of levator)
To close: orbicularis occuli (CN VII – see face)
NIGEL FONG 2011/2012
PAGE A292
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!!!!!!!!
Glands of the eyelid
•
•
•
!
Tarsal glands on inner surface of eyelid: sebaceous secretion (sticky stuff in morning)
- Lubricate eyelid edges, preventing adhesion, and keep lacrimal fluid inside
Ciliary glands on edge of eyelid: modified sweat glands
Clinical: Blockage & inflammation of tarsal glands (chalazion) vs ciliary glands (stye)
can be differentiated by location
!
Conjunctiva
•
•
Conjunctival sac enables eyelids to move freely over surface of eyeball. Formed by:
- Palpebral conjunctiva: transparent mucus membrane covering eyelids
- Bulbar conjunctiva: Reflected at sup & inf fornices onto the ant surface of eyeball.
Its epithelium is continuous with cornea
Normally colourless, unless vessels dilated & congested e.g. irritation, conjunctivitis.
Lacrimal gland & fluid
•
•
Lacrimal fluid: saline secretion to lubricate conjunctiva & cornea. In excess = tears
- With lysozyme: antibacterial
- Also provides nutrients & dissolved oxygen to the avascular cornea
Lacrimal gland lies in fossa for lacrimal gland in sup/lat part of orbit, near lat
margin of levator palpebrae superioris tendon.
- Lacrimal fluid exits gland via excretory ducts, flowing into sup conjunctival fornix
- Circulate medially across the cornea with blinking, collecting at lacrimal lake
- Drain thru lacrimal pumctum, lacrimal canaliculi, lacrimal sac, and nasolacrimal
duct to inf nasal meatus to be swallowed.
!
!
NIGEL FONG 2011/2012
PAGE A293
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
B. CONTENTS OF THE ORBIT
!
Eyeball & spaces
•
•
•
•
Eyeball is much smaller than the orbit
- Suspensory ligament of eyeball forms a hammock-like sling to support it.
Structures of orbit embedded in orbital fat
Position of eyeball indicative of pathology
- Exopthalmos (protrusion): Graves disease, orbital tumors
- Inopthalmos (retraction): Starvation reducing retrobulbar fat
Ciliary ganglion located at pos part of orbit
Blood vessels
•
Opthalmic artery: from int carotid art, enters orbit through optic canal.
•
- Gives central artery of retina (see eyeball)
Sup & inf opthalmic veins, draining into cavernous sinus
•
- Communication with facial vein: see danger area of face
No lymph nodes in the orbit (after all the eye is an extension of the CNS, which does
not have lymph nodes)
!
!
!
NIGEL FONG 2011/2012
!
PAGE A294
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Opthalmic nerve (CN V1)
•
General sensory function
- CN II, III, IV, VI for special sensation, somatic & visceral motor – see later)
Frontal n: passes on roof of orbit, sup to levator palpebrae sup, dividing into:
•
- Supratrochlear n: wind around upper margin of orbit to supply skin of forehead
- Supraorbital n: exits to face through sup orbital fissure/foramen
Nasocillary n: cross abv optic n, runs along upper margin of med rectus
•
- Gives ant/pos ethmoidal n to nose
- Cutanoues n: infratrochlear & ext nasal n (fr ant ethmoidal)
Lacrimal nerve: travels on upper border of lat rectus
•
-
Cutanous supply to skin
Carries visceromotor fibres to lacrimal gland (receives parasympathetics fr CN VII)
!!!!!!
!
Identification & relations
•
Superior view
•
Anterior view
-
Sup most: Frontal n, Sup opthalmic vein
Ctr: Levator palpebrae sup above sup rectus
Med: Sup oblique above med rectus
Lat: Lacrimal gland & lat rectus
Inferior/anterior: inf oblique
!
!
NIGEL FONG 2011/2012
PAGE A295
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
C. DEVELOPMENT OF THE EYE
Growth of the optic cup
•
•
Eye grows out of neuroectoderm of forebrain as the optic vesicle (week 3)
Optic vesicles invaginates to form the optic cup
-
•
Inner layer forms neural layer of retina (rods, cones, ganglion cells etc)
Outer layer forms pigmented layer of retina
Layers initially separated by intraretinal space but later appose each other
Optic cup connected to brain by optic stalk, which becomes optic nerve
-
Surrounded by dura (continuous with sclera), pia & arachnoid (cont w choroid)
Invagination of optic cup also involves inf surface, forming the choroid fissure which
contains the hyaloid artery (later becomes ctrl artery of retina)
Closure of choroid fissure and further growth of optic nerve results in the central
artery of retina being contained within the optic nerve.
Surrounding structures
•
•
•
Optic vesicles induce surface ectoderm to form lens placode (plate)
- Lens placode later leaves surface ectoderm to lie in the optic cup
Mesenchyme in the region forms iris, ciliary body, sphincter pupillae, dilator pupillae,
choroid, sclera.
Cornea formed fr surface ectoderm (gives epithelium) as well as mesenchyme (deeper
layers of cornea)
Defects related to development
•
•
•
Retinal detachment: As the 2 layers of the retina are not firmly attached, they can
detach due to seepage of fluid after trauma – pt sees flashes of light / floating specks.
Coloboma: choroid fissure fails to close, resulting in a persistent cleft (iris only, may
extend into ciliary body, retina, choroid, optic nerve). Can also arise fr injury
Congenital cataracts: lens opacification, assoc w maternal rubella during pregnancy
! Retinal detachment
Coloboma "
NIGEL FONG 2011/2012
PAGE A296
M1 NOTES IN GROSS ANATOMY
D. STRUCTURE OF THE EYEBALL
8 | BRAIN, HEAD & NECK
!
Opthalmoscopic view
!
!
Outer fibrous layer
•
•
Sclera posteriorly: tough opaque layer, continuous w dura of CN II
Cornea anteriorly: transparent, more convex, appearing to protrude from ant surface
-
!
Avascular, nourished by lacrimal fluid & aq humor
Primary refractive medium of the eye, with greatest degree of refraction
Blink reflex: Cornea is v sensitive to touch (supplied by CN V1). Touching w wisp
of cotton should trigger orbicularis occuli contraction (CN V1 & CN VII patent)
Middle vascular layer
•
•
Choroid posteriorly: vascular bed giving ‘red eye’ in photos.
Ciliary body anteriorly: connects choroid with iris, provide attachment of lens
•
- Accomodation: smooth muscle of ciliary body controls thickness of lens
Iris: thin ant diaphragm with pupil (central aperture), allowing light to pass through
-
Pupil diameter controlled by sphincter pupillae & dilator pupillae
Inner retina
•
Outer pigmented layer (reduce scattering of light) & inner neural layer (CN II)
Fovea centralis in the macula (macula lutea, yellow spot), lateral to optic disc, is the
area of most acute vision (has greatest density of cones and no rods - see CN II)
Optic disc: Where optic nerve enters the eyeball
•
- Optic disc has no photoreceptors, insensitive to light (“blind spot”)
Optic nerve (CN II) exit orbits through optic canals
•
- Optic sheath: Surrounded by ext of cranial meninges, subarachnoid space (w CSF)
- Dura of optic sheath continuous with sclera of eye
Central artery of retina (branch of opthalmic art) runs within optic sheath
•
•
-
End artery supplying retina
Accompanied by central vein of retina, draining into cavernous sinus
Clinical: Increase in CSF pressure causes edema of the retina, viewed during
opthalmoscopy as swelling of optic disc (papilledema)
NIGEL FONG 2011/2012
PAGE A297
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Aqueous humor
•
•
•
•
Function: Clear fluid supporting wall of eyeball by exerting internal pressure.
- Also nourishes avascular cornea & lens.
Fills the space between the lens & the cornea
- Space divided into ant & pos chamber by the iris/pupil
Flow of aq humor:
- Secreted into pos chamber by ciliary processes of ciliary body
- Passes into ant chamber through pupil
- Drains at iridocorneal angle into the scleral venous sinus (canal of Schlemm)
Clinical: Glaucoma: increase in intra-ocular pressure due to blockage of outflow
-
!!
Open-angle: due to blockage of trebeculae or scleral venous sinus
Close-angle: when iris obstructs outflow of aqueous humor
Compresion of retinal arteries can ↓ blood SS to retina, causing blindness (vision is
lost from periphery first because that is where retinal artery pressure is lowest)
Lens
•
Transparent biconvex structure pos to iris, ant to vitreous humor
- Elastic capsule anchored by zonular fibres (suspensory ligament of lens) to
encircling ciliary process (unattached lens is nearly spherical)
- Cataracts: when lens becomes opaque
•
Accomodation: shape of lens changes for near vision
- Far vision: no nerve stimulation, ciliary muscle relaxed, zonular fibres under
tension. Lens stretched thin & less convex, allowing less refraction of parallel rays
- Near vision: parasympathetic stimulation contracts ciliary muscle, zonular fibres
relax. Lens more convex, refracting divergent rays from a near object more.
- Clinical: Presbyopia - Ability to accommodate restricted after age 40.
!
Vitreous humor
•
•
Tranparent gel filling eyeball behind lens
Function: contribute slightly to magnifying power of eye, support pos surface of lens,
holds neural part of retina against pigmented part.
NIGEL FONG 2011/2012
PAGE A298
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
E. AUTONOMIC INNERVATION OF EYE
!
Nerve supply of lacrimal gland
PARASYMPATHETIC
SYMPATHETIC
Secretomotor, drive secretion
Vasoconstrict
CN VII nervus intermedius
Lacrimal nucleus
Presynaptic: T1 intemedio-lateral nuc
Postsynaptic: T1 sympathetic ganglion
ROUTE
CN VII nervus intermedius
Greater petrosal n
Sympathetic trunk, sup cervical ganglion,
int carotid plexus, Deep petrosal n
GANGLION
Pterygopalatine ganglion:
synapse onto postsynaptic
COMMON
Zygomatic n (fr CN V2) carry fibres to lacrimal n (fr CN V1) to lacrimal gland
FUNCTION
ORIGIN
Merge to form nerve of pterygoid canal (Vidian nerve)
Pass through, do not synapse
!
!
!
!
Nerve supply of intraoccular muscles
PARASYMPATHETIC
SYMPATHETIC
FUNCTION
Constricts pupil in response to bright light
- stim sphincter pupillae
Accomodation of lens: ciliary mus contract
Dilates pupil in response to dim light:
- stim dilator pupillae
ORIGIN
CN III: Edinger-Westphal nucleus
T1 via sym trunk, int carotid plexus
GANGLION
Synapse on ciliary ganglion
Pass through without synapsing
ROUTE
Via short ciliary nerve to eyeball
Via long ciliary nerve to eyeball
!
Pupillary light reflex
•
Shining light into pupil results in constriction of both
L/R pupils
1. Retinal ganglion cell detect light, transmit signal via
optic n to pretectal nucleus of midbrain
2. Signal transmitted to L/R Edinger-Westphal nucleus
- Contralateral nuc reached via pos commissure
3. Preganglionic parasympathetic fibres of CN III travel
to ciliary ganglion and synapse
4. Postganglionic parasympathetic fibres enter iris to
supply sphincter pupillae, so pupil constricts
• Pupils may also dilate in response to emotional state due to sympathetic activation
!
NIGEL FONG 2011/2012
!
!
PAGE A299
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Accomodation (and Convergence)
•
•
Accomodation reflex brings closer objects onto focus on the retina
- Lens thickening (ciliary muscles): greater refraction focuses divergent rays on retina
- Pupillary constriction (sphincter pupillae): eliminate stray light
- (Con)Vergence of eyes (medial rectus): look together towards near object
Visual association cortex analyses object and passes signals down sup colliculus to
- Edinger-Westphal nucleus, then via ciliary ganglion to ciliary muscles & sphincter
pupillae
- Oculomotor nucleus (CN III) for stimulation of medial rectus
!
F. EXTRAOCCULAR MUSCLES
!
= 4 recti (med/lat/sup/inf), sup/inf oblique, and levator palpebrae superioris
Levator palpebrae superioris
•
•
•
Opens the upper eyelid: opposed by gravity & orbicularis occuli
Includes both skeletal muscle & smooth muscle (sup tarsal muscle)
- Skeletal muscle: Innervated by CN III
- Smooth muscle: Innervated by sympathetics from T1 via cervical sym trunk
Clinical: Ptosis (drooping of upper eyelid) can result from
-
CN III lesion (see CN III)
Horner syndrome: interruption of cervical sympathetic trunk, which also causes
miosis (pupillary constriction), vasodilation, and anhydrosis (no sweating).
!
!
!
Attachments of the extra-occular muscles
•
•
Recti muscles arise from common tendinous ring surrounding optic canal and attach to
sup, inf, med, lat aspects of anterior eyeball
Obliques: line of pull is from the ant/med orbital rim, attaching to the pos/lat eyeball
- Inf oblique originates directly from ant/inf orbital rim, lat to lacrimal fossa
- Sup oblique originates similar to recti, but its tendon goes through a trochlea at
the sup/med orbital rim, which redirects its line of pull.
!
NIGEL FONG 2011/2012
PAGE A300
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
Actions of extraoccular muscles
•
•
•
•
•
!
Movements are described starting with eyes in primary position (looking ahead);
Rotation is described in terms of movement of sup pole of eyeball
Intuitive action of recti muscles
- Med rectus adducts, Lat rectus abducts
- Sup rectus elevates, Inf rectus depresses
Recti approach eyeball from medial side as axis of orbit & recti is laterally directed
- Sup/inf recti adduct.
- Sup rectus rotates sup pole of eyeball medially: i.e. intorsion (medial rotation)
Inf rectus rotates inf pole of eyeball medially: i.e. extorsion (lateral rotation)
Since obliques pull from ant/med and attach to pos & lat part of eyeball,
- Sup oblique depresses & inf oblique elevates (opposite action vs if they attach ant)
- Both obliques abduct the eye (but not very well until lat rectus initiates)
- Sup oblique rotates sup pole of eye medially i.e. intorsion, inf oblique rotates inf
pole of eye medially, i.e. extorsion
Muscles act together as synergists (combined actions: see diagram).
- Rotation normally cancels out
Clinical testing of extraoccular muscles & nerve supply
•
•
•
Test sup/inf recti: look laterally, up/down.
- In this position, angle of gaze coincides with plane of muscle, and the recti are
solely responsible for elevation/depression
Test sup/inf oblique: look medially, down/up (note: sup oblique looks down)
- In this position, obliques solely responsible for elevation/depression
Med/lat rectus cannot be tested in isolation.
!
!
!
!
!
NIGEL FONG 2011/2012
!
PAGE A301
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
G. CN III, IV, VI: OCULOMOTOR, TROCHLEAR, ABDUCENS NERVE
!
CRANIAL N
III
Oculomotor
FIBRE
SUPPLY
1º NEURON
2º NEURON
Som Mot
Extraoccular musc except
sup oblique & lat rectus
Oculomotor nuc
Parasym
Sphincter pupil, ciliary mus
Edinger-Westphal
Ciliary ganglion
-
IV
Trochlear
Som Mot
Sup oblique muscle
Trochlear nuc
-
VI
Abducens
Som Mot
Lat rectus muscle
Abducens nuc
-
Mnemonic for nerve supply: SO4 LR6 AllOthers3
Course of CN III, IV, VI
•
•
Exit from brainstem
- CN III exits occulomotor nucleus at midbrain (level of sup colliculus), travel btw
cerebral peduncles
- CN IV exits trochlear nucleus, crosses midline, leaves roof (pos) of lower midbrain
(level of inf colliculus), then wrapping around lat aspect of cerebral peduncle
- CN VI exits abducens nucleus at pontomedullary junction
All pass thru cavernous sinus (directly through: CN VI, through lat wall: CN III, IV)
- All enter orbit through sup orbital fissure, CN III divides into branches.
!
!
Effects of lesion
•
•
•
•
CN VI lesion: paralysis of lat rectus (abducts)
- Eye cannot abduct, adducted at rest due to unopposed med rectus
CN IV lesion: paralysis of sup oblique (depresses, abducts, intorts)
– Elevation of eye on forward gaze due to unopposed inf oblique
– Extent of elevation increased w adduction
CN III lesion: paralysis of all extraoccular muscles except lat rectus & sup oblique
- Ptosis (dropping of upper eye lid) due to impaired levator palpebrae sup
!
- Fully dilated pupil, unreactive to pupillary light reflex (CN III supplies sphincter)
- Lat deviation - unopposed lat rectus (this alone if muscle paralysis, not CN lesion)
Diplopia (double vision) present for all lesions when looking twds affected side: 1 eye
can look but the other cannot.
Abducens paralysis:
Oculomotor paralysis:
!
NIGEL FONG 2011/2012
PAGE A302
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Eye movements
•
•
•
Eyes move to keep object stationary on fovea (foveation), even if object or head moves
Disconjugate movement: in accomodation, both medial recti act.
Conjugate movements: eyes move as a pair, in same direction and by same amount
-
•
!
Saccades (scanning): flick from 1 visual target to another
Tracking (smooth pursuit): follow object of interest across visual field
Complex control: reflexive control by separate nuclei for each subtype of eye
movement, or voluntary control by cortex
Vestibulo-Ocular reflex maintains foveation despite head
movements
- Receptors in semicirculator canals of ear detect rotational
acceleration
- Vestibular nuclei send signals to occular motor nuclei
- Eyes move in opposite direction to keep image on retina
!
F. CN II: OPTIC NERVE
CRANIAL N
FIBRE
SUPPLY
1º NEURON
2º NEURON
II
Spec Sen
Vision: Retina
Retina ganglion
cells
Thalamus: lat
geniculate nuc
Optic
!
Photoreceptors
•
Photoreceptors consist of outer (disks w rhodopsin) & inner segment (mitochondria)
- Rods: sees black & white, sensitive to dim light. None in fovea.
-
•
•
Cones: sees colours & detail, only in bright light. Concentrated in fovea
Dark current: when unstimulated by light, cGMP binds cGMP-gated ion channels.
Photoreceptors are depolarized and release glutamate to bipolar cells
Photoreceptors hyperpolarized by light
- Rhodopsin absorbs photon, causing cis/trans isomerization of retinal
- G protein is bound, bound G protein then activates transducin [amplification]
- Transducin activates phosphodiesterase, which hydrolyses cGMP [amplification]
- cGMP-gated channels close. Photoreceptor hyperpolarizes, less glutamate released
Signal transmission in retina
•
•
•
Photoreceptors (2, 3) conv light energy to action pot
- Cones coded for red, green, blue.
- Rods coded on/off.
Bipolar cells (5) transmit info to ganglion cells (7)
Axons of ganglion cells form optic nerve (CN II)
-
•
Acquire myelin sheath as nerve leave optic disc
Optic n is part of CNS: contain astrocytes &
oligodendrocytes (not Schwann cells of PNS),
invested with cranial meninges.
Signal integrated by horizontal & amacrine cells (5)
NIGEL FONG 2011/2012
!
1: Pigment layer | 2-8: Neural layer
PAGE A303
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
Visual pathway
•
•
•
•
Binocular vision provides a 3D image for gauging distances.
- 2/3 of visual field is binocular: 2 eyes overlap
- Outer 1/6 on each side is monocular
Visual image is inverted & reversed by cornea/lens
- L visual field = R retinal field; upper visual field = lower retinal field
Vision is a crossed sensation: R visual cortex sees L visual field.
- Fibres fr nasal hemiretina (view temporal vis field) : decussate at optic chiasm
- Fibres fr temporal hemiretina (view nasal vis field) : uncrossed, stay ipsilateral
Axons from CN II terminate in lateral geniculate body of the thalamus
-
•
Collateral br to midbrain
: sup colliculus (visual reflexes)
: pretectal nucleus (pupillary reflex, accomodation)
Optic radiation (geniculo-calcarine tract) relay visual information from thalamus
LGB to 1º visual cortex (see cerebral cortex)
- Meyer’s loop: fibres fr sup visual field (inf retinal quadrants) sweep fwd into
temporal lobe before turning back. May be affected by stroke of temporal lobe
- 1º visual cortex on banks of calcarine sulcus, L/R eyes rep. in alternating stripes.
!
!
!
NIGEL FONG 2011/2012
PAGE A304
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Visual pathway lesion
•
•
•
Patients may be unaware of extensive blindness:
in affected area, patient does not see blackness,
patient sees nothing
Visual injury described in terms of patient’s
viewpoint i.e. visual fields
Confrontation testing: pt sits opposite examiner
and focuses on examiner’s nose, while examiner
brings a wriggling finger into view from the
periphery.
Presentation of lesion
Lesion in:
• Optic n (1, 2)
: 1 eye blindness (whole or part, i.e. scotoma)
• Optic chiasm (3) : Bitemporal hemianopia (e.g. with pituitary adenoma)
!
: Homonymous hemianopia (same on both sides)
•
Optic tract (4)
•
•
Meyer’s loop (4) : Homonymous upper quadrantanopia (eg tumors impinging fr below)
Lesions close to visual cortex (6-8) may present with macular sparing
- Area of cortex corresponding to macula supplied by both pos & middle cerebral
artery, hence does not infarct
Note if optic tract / visual cortex, hemianopia is on contralateral side.
•
NIGEL FONG 2011/2012
PAGE A305
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
7. NOSE
!
A. EXTERNAL & SKELETAL FEATURES
External nose
•
•
•
Surface description:
Dorsum ext fr root to apex; nares (nostrils) bounded by alae
Skeleton:
Bones (Nasal, frontal, maxillary) + cartilage
Thin skin of face extends into vestibule of nose, which has hairs to filter dust particles
!
Boundaries of nasal cavity
•
•
•
Roof:
Floor:
Med:
Nasal, frontal, ethmoidal (cribiform plate), sphenoidal bones
Palatine process of maxilla, horizontal plates of palatine bone
Nasal septum: bony part (ethmoid, vomer) + soft mobile cartilaginous part
•
•
Lat:
Pos:
Nasal chonae: sup, middle (ethmoid bone), inf (separate bone)
Opens into nasopharynx through choanae
Lat:
Med (septal):
!
NIGEL FONG 2011/2012
PAGE A306
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
A/P view:
Lateral view:
!
!
Paranasal sinuses
•
•
•
•
Air-filled extensions of respiratory part of nasal cavity into adjacent bones
- Respiratory epithelium extends into the sinuses
Frontal sinus: btw inner & outer tables of frontal bone
Ethmoidal sinus (cells): ant / middle / pos invaginations into the ethmoid bone
Sphenoidal sinus: in body of sphenoid, may extend into wings.
-
•
Closely related to optic nerves / chiasm, pituitary gland, cavernous sinus & int
carotid art, separated only by thin bone
- Clinical: Pituitary may be surgically accessed from nose, via the sphenoidal sinus
Maxillary sinus: in body of maxillae
-
Closely related to roots of maxillary teeth: can be damaged during extraction
Most commonly infected: sinus located inferior to its opening into the nasal cavity,
hence does not drain easily
B. INTERNAL FEATURES
Nasal conchae
•
•
•
!
Also see:
Histology of nose
in Histology
Nasal conchae (sup, medial, inf) hang like curtains from the lat wall, curving inferiorly
- Func: create turbulent flow to precipitate particles, ↑ surf area to warm air
Nasal meatus (sup, middle, inf) lie below their conchae.
Sphenoethmoidal recess: sup to sup concha (tog w sup concha, hv olfactory epithelium)
NIGEL FONG 2011/2012
PAGE A307
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
Openings into the nasal meatus
•
•
•
•
Sphenoethmoidal recess : sphenoid sinus
Sup nasal meatus
: pos ethmoid sinus
Inf nasal meatus
: nasolacrimal duct, pharyngotympanic tube posteriorly
Middle meatus
: everything else
- Bulla: formed by middle ethmoidal sinus
-
Hiatus semilunaris: infundibulum opening of frontal sinus.
-
Maxillary sinus has a small opening in floor of hiatus semilunaris
Spread of infections
•
!
Rhinitis (swollen & infected mucosa) may spread via openings to:
-
Paranasal sinuses, causing sinusitis and local pain (esp maxillary sinus)
-
Nasopharynx
Ant cranal fossa: thru cribiform plate
Middle ear: thru pharyngotmpanic tube
Lacrimal apparatus & conjunctiva: thru nasolacrimal duct
• Infection of ethmoidal cells may also break through fragile medial wall of orbit,
spreading to the orbit and affecting the optic nerve
NIGEL FONG 2011/2012
PAGE A308
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
C. VASCULATURE & INNERVATION
!!!!!
Blood supply
•
•
•
•
!
Arterial supply from branches of both ext & int carotid
- Fr opthalmic art
: Ant & pos ethmoidal art
- Fr maxillary art
: Sphenopalatine art
: Greater palatine art (via incisive canal thru ant hard palate)
- Fr facial art
: Septal branch of sup labial art
Little’s / Kiesselbach area: Arterial anastomosis
- Clinical: Epistaxis (nosebleed) commonly arises from this area. But if persistent,
check for ant cranial fossa bleed or nasopharyngeal cancer.
Submucosal venous plexus warms inspired air
- Drains into accompanying veins, comm. w cavernous sinus (see danger area of face)
Lymphatics: ext part to submandibular nodes, deep parts to upper deep cervical nodes
!
CRANIAL N
FIBRE
SUPPLY
1º NEURON
2º NEURON
I
Spec Sen
Smell
Olfac epithelium
*
Olfactory
!
Innervation of the nose
•
•
Special sensation (Smell): Olfactory epithelium supplied by olfactory nerve (CN I)
General sensation: Branches of facial nerve (CN V)
- Ant/sup: fr opthalmic n (CN V1) - nasociliary n – ant/pos ethmoidal n
-
Pos/inf: fr maxillary n (CN V2) – nasopalatine nerve & greater palatine n
Frontal & ethmoidal supplied by CN V1, Maxillary by CN V2, Sphenoidal by both
!
NIGEL FONG 2011/2012
PAGE A309
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
8. MASTICATORY APPARATUS & ORAL CAVITY
A. PTERYGOPALATINE FOSSA
!
!
!
Boundaries & Contents
•
•
Small pyramidal space inf to apex of orbit, medial to infratemporal fossa
- Btw pterygoid process of sphenoid, pos aspect of maxilla
Distributes nerves & vessels to other compartments via many connections (below)
- Pterygopalatine part of maxillary artery (see maxillary artery)
- Maxillary nerve
- Pterygopalatine ganglion
!
NIGEL FONG 2011/2012
PAGE A310
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
!
Maxillary nerve (CN V2)
•
•
Purely sensory nerve supplying cheeks, nasal cavity (and maxillary sinus), upper jaw
Leaves skull via foramen rotundum to enter pterygopalatine fossa
•
Branches emerge from pterygopalatine fossa
- Zygomatic n: SS skin of lat cheek / temple (via zygomatico-temporal & -facial n)
- Greater & lesser palatine nerve: through palatine canal to roof of oral cavity
- Branches to nose: nasal nerve, nasopalatine nerve
- Alveolar nerves: branches from maxillary n in pterygopalatine fossa and from inf
orbital n together form sup dental plexus to SS maxillary teeth
Leaves pterygopalatine fossa as inf orbital fissure, becoming inf orbital nerve
•
•
- Nasal, palpebral, sup labial branches supply skin of face in V2 dermatome
Gives pterygopalatine ganglion (see lacrimal gland) in the pterygopalatine fossa
- Contains parasympathetic postsynaptic cell bodies SS lacrimal gland, nasal,
palatine, pharyngeal glands
B. TEMPOROMANDIBULAR JOINT & MUSCLES OF MASTICATION
!
Regions
•
•
•
Temporal fossa: lateral area of scalp sup to zygomatic arch, overlying the pterion
- Occupied primarily by temporalis muscle
Infratemporal fossa: deep & inf to zygomatic arch, pos to maxilla
- Deep to ramus of mandible: visible only when ramus of mandible removed
Foramen ovale exits to the infratemporal region
- Foramen ovale may be accessed when jaw is open or via vestibule of mouth
!
NIGEL FONG 2011/2012
!
PAGE A311
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Temporomandibular joint
•
•
•
•
Synovial modified hinge joint btw
- Mandible: head (condyle)
- Temporal bone: mandibular fossa & articular tubercle
Contains fibrocartilaginous articular disc
- Creates sup/inf compartments, lined by separate synovial membranes
- Articular surface covered by fibrocartilage instead of hyaline cartilage (unusual)
Supporting ligaments: lateral, sphenomandibular & stylomandibular
- Lat ligament prevents complete opening by hinge movement only
Nerve supply: auriculotemporal nerve (from CN V3)
!
Movements of the TMJ
•
•
•
!
Fully opening the mouth requires an intial rotation, followed by protraction
Hinge movements (elevation & depression / rotation) occur in inf cavity
- Depression: head of mandible rotates on articular disc
Gliding movements (protrusion & retrusion / translation) occur in sup cavity
- Protrusion: head of mandible moves anteriorly on articular surf
- Side-to-side chewing mvmt: protraction on 1 side deviates jaw to opposite side
Clinical notes
•
Dislocation of TMJ: when taking a large bite
or yawning, the head of mandible may slide
anteriorly, out of condylar fossa and over the
articular tubercle. Muscles hold jaw in its
dislocated position and the mouth cannot close.
!
•
•
•
To reduce ant dislocation of mandible, mandible must be pulled downwards before
putting it back.
Fracture: Blow to chin with mouth closed can drive head of mandible pos/sup
- May fracture floor of middle cranial fossa or bony auditory canal
Ankylosis: rheumatoid arthritis, infectious agents, neoplasia, trauma may result in
unilateral or bilateral loss of movement
Pain in TMJ may be referred from elsewhere
!
NIGEL FONG 2011/2012
PAGE A312
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Muscles of mastication
•
•
•
Muscles of mastication develop from 1st pharyngeal arch
- Hence are innervated by nerve of 1st arch: CN V3 (Motor root of mandibular n)
Powerful muscles close the mouth (all except lateral pterygoid)
- Opening of mouth is primarily by gravity, assisted by strap muscles of neck
(suprahyoid & infrahyoid).
Identification & key relations:
- Lateral pterygoid has horizontal fibres and is more superficial while medial
pterygoid has vertical fibres and is deeper
- Medial pterygoid usually tendinous
- Br of CN V3 (inf alveolar & lingual n) emerge from btw medial & lateral pterygoid
!!
!
MUSCLE
ORIGIN
INSERTION
Temporalis
Temporalis fossa / fascia
Mandible: coronoid
process & ramus
Masseter
Zygomatic arch
Mandible: angle &
ramus (lat side)
Lat pterygoid plate: med side
Maxilla
Mandible: ramus &
angle (med side)
Lat pterygoid plate: lat side
Sphenoid: greater wing
Mandible: neck, jt
capsule, artic. Disc
Med pterygoid
NERVE
CN V3
Lat pterygoid
!
ACTION
Retract
Elevate
Depress
Protract
Side mvmt
!
Note: Digastric is not a muscle of mastication, but it helps to open the mouth.
Supplied by closest motor nerves: Ant belly SS by CN V3, Pos belly by CN VII
NIGEL FONG 2011/2012
PAGE A313
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
C. INFRATEMPORAL FOSSA: NEUROVASCULATURE
!
!
!
!!
Maxillary artery
•
•
Largest branch of external carotid supplying nasal cavity & sinuses, lateral wall & roof
of oral cavity, all teeth, and dura mater.
- Originates from ext carotid in substance of parotid gland.
- Passes through infratemporal fossa (either adj or deep to lat pterygoid)
- Disappears into pterygomaxillary fissure, enters pterygopalatine fossa
Branches from either infratemporal or pterygopalatine fossa
- Middle meningeal art
: To dura mater
- Inf alveolar art
: To mandibular teeth (via mandibular foramen)
- Sup alveolar art
: To maxillary teeth
- Greater palatine art
: To hard palate (gives less. palatine art to soft palate)
- Sphenopalatine art
: To nose (via sphenopalatine foramen)
- Infra-orbital art
: To face
Pterygoid venous plexus
•
•
•
!
In infratemporal fossa btw med &
lat pterygoid & temporalis
Drains areas SS by maxillary art:
Communicates with
- Cavernous sinus via emissary v
- Facial vein
- Possible route for spread of
infection
!
!
!
!
!
NIGEL FONG 2011/2012
PAGE A314
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Mandibular nerve (CN V3)
•
Supply:
- Sensory: lower jaw (with proprioception), lower teeth, gums, inner surface of cheek,
ant 2/3 tongue, ext auditory meatus & ext tympanic membrane
- Motor: Muscles of mastication
Leaves skull via foramen ovale to enter infratemporal fossa, splitting into ant/pos div
•
- Ant division: branches to muscles of mastication & buccal nerve to skin of cheek
- Pos division: auriculotemporal, lingual, and inf alveolar nerve.
Auriculotemporal nerve: to skin of auricle, ext auditory meatus, TMJ, scalp
•
- Carries CN IX parasympathetics fr otic ganglion to parotid gland
Lingual nerve: enters mouth, runs fwd on side of tongue.
•
-
•
Responsible for general sensation on ant 2/3 of tongue
Joined by chorda tympani fr CN VII: carries taste from ant 2/3 of tongue,
parasympathetics to submandibular & sublingual glands
Inf alveolar nerve: enters mandibular foramen (medial side ramus) to SS teeth
-
Terminates as mental nerve, emerging through mental foramen to SS skin of chin
Identification: lies inf to lingual n, disappears into the mandible
Clinical: closely related to 3rd molar, may be damaged in clumsy extraction
Clinical: anesthetic injection often used by dentists to anesthetize lower jaw
!
Pos division:
!
Ant division:
!
!
!
!
NIGEL FONG 2011/2012
PAGE A315
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Relations
!
!
!
NIGEL FONG 2011/2012
PAGE A316
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
D. ORAL CAVITY
!
Mouth
•
Lips: formed by orbicularis oris, covered ext by skin and int by mucus membrane.
- Philtrum: shallow vertical midline groove on outer surf of upper lip
Vestibule: between lips/cheeks and teeth/gums.
•
- Lat wall formed by cheek (buccinator muscle)
Oral cavity proper: bounded by teeth/gums, hard/soft palate (roof), tongue (floor)
•
•
Mylohyoid (fr med border of mandible to hyoid bone)
•
- Supports floor of mouth, raises floor of oral cavity when swallowing
- Supplied by CN V3
Pos limit of oral cavity: Oropharyngeal isthmus marked by palatoglossal fold
•
Sensory supply of oral cavity
- Maxillary part: by CN V2, via sup alveolar nerves (ant/mid/pos)
- Mandibular part: by CN V3, via lingual n, inf alveolar n, buccal n (lat side)
!!!!!!!!!!!!!
Teeth
•
•
•
Anchored individually in sockets (alveoli) in alveolar processes of maxillae & mandible
by periodontal ligament
20 deciduous (milk) teeth: 4 sides x 2 incisors, 1 canine, 2 molars
32 permanent (adult) teeth: 4 sides x 2 incisors, 1 canine, 2 premolars, 3 molars
- Third molars (wisdom teeth) may be unerupted or congenitally absent
!
NIGEL FONG 2011/2012
PAGE A317
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!!
Tongue
!
•
Ant 2/3: Rough due to fungiform (no taste buds) & filiform papillae (with taste buds)
- Frenulum on underside: mucosal fold connecting tongue to floor of mouth
•
Pos 1/3 (root): forms ant wall of the oropharynx
- Dorsum of pos 1/3 covered by lymphoid nodules of lingual tonsils.
•
Sulcus terminalis forms V-shaped division btw ant 2/3 and pos 1/3
-
•
Circumvallate papillae (with taste buds) ant/parallel to sulcus terminalis.
Foramen cecum forms blind ended depression at center of V: vestigial structure
of thyroid diverticulum, which dvp fr foramen cecum and migrates to ant neck
Intrinsic muscles change shape of tongue:
- Sup & inf longitudinal, transverse, vertical fibres, all supplied by CN XII
Development & nerve supply
•
•
Tongue dvp at base of pharyngeal arches, carrying nerve SS of respective arches along
- Median lingual swelling may be present
Tongue is freed from floor of mouth by apoptosis at base of tongue
- Clinical: Ankyloglossia (tongue-tie) e.g. frenulum extending to tip of tongue can
result if apoptosis is incomplete. This impairs articulation of words
!
PART
DERV
DEVELOPMENT
Ant 2/3
1 pharyngeal
arch
2 lat lingual swellings overgrow
median lingual swellings to fuse in
midline (indicicated by median sulcus)
Pos 1/3
Arches 2-4
(hypobranchial
eminence)
3rd arch overgrows 2nd arch and
fuses with 1st arch at sulcus terminalis
Occipital somite
Mesoderm origin, migrate to tongue
Muscles
st
GEN SENS
CN V3
Lingual n
TASTE
CN VII chorda
tympani, joining
lingual n
--- CN IX --(both modalities)
Small caudal area ant to epiglottis
derv fr 4th arch
CN X:
int laryngeal n
MOTOR:
CN XII
!
NIGEL FONG 2011/2012
PAGE A318
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!!!!!
!
Extrinsic muscles of tongue
•
•
•
Responsible for changing position of tongue
All supplied by CN XII except palatoglossus which receives same nerve supply as the
rest of the muscles of the soft palate.
Clinical: if genioglossus is paralyzed (e.g. in general anesthesia), tongue will tend to to
fall posteriorly, obstructing the airway. Hence airway is inserted in anesthesized person
to prevent tongue from relapsing.
!
MUSCLE
NERVE
Genioglossus
Hyoglossus
Mandible: inner surf
CN XII
Styloglossus
Palatoglossus
ORIGIN
CN X
Hyoid bone
Temporal: styloid
proc
Soft palate: palatine
aponeurosis
INSERTION
Blends with
muscles of
tongue
Side of tongue
ACTION
Protrudes tongue
Depress tongue
Draws tongue up, curl backward
Pulls tongue up/back, narrows
oropharyngeal isthmus
Blood supply of tongue
•
Lingual art: fr ext carotid
•
- Passes deep to hyoglossus (while lingual & hypoglossal nerves are superficial)
- Gives branches: dorsal lingual, deep lingual
Lingual vein: sup to hyoglossus, w hypoglossal n
•
Deep lingual veins run on underside of tongue
-
Clinical: deep lingual v rapidly absorbs drugs placed under the tongue, e.g.
nitroglycerin as a vasodilator for angina pectoris
Lymphatic drainage of tongue
•
•
•
•
Apex & frenulum drains to submental nodes
Ant 2/3 drain to submental & submandibular node
Pos 1/3 drains directly to deep cervical nodes
(eventually all drain to deep cervical nodes
Rich anastomosis across midline: tumour on one
side easily metastasizes to contralateral nodes
!
!
NIGEL FONG 2011/2012
PAGE A319
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
E. SUBMANDIBULAR REGION
Lingual nerve in submandibular region
•
•
•
Carries fibres from CN V3 and CN VII chorda tympani
- To ant 2/3 of tongue: Gen sensory (fr CN V) and taste (fr CN VII chorda tympani)
- To submandibular & sublingual glands: parasympathetic fibres (fr CN VII)
Passes through gap btw mylohyoid, sup & middle constrictor muscles
Enters floor of mouth, superficial to hyoglossus, loops under submandibular duct
Salivary glands
•
!!!!!
!!!
!
Submandibular gland (mixed serious & mucus)
-
•
Beneath lower border of body of mandible
Div into sup & deep parts by mylohyoid, curves around pos border of mylohyoid.
Deep part cont as submandibular duct, opening at base of frenulum of tongue
Closely related to facial artery, lingual (fr CN V3), hypoglossal (CN XII), and
marginal mandibular (fr CN VII) nerves
Sublingual gland (mostly mucus)
•
- Lies beneath mucus membrane on floor of mouth, btw mandible & genioglossus
- Multiple sublingual ducts open into mouth
Parotid gland (serous) is separate, opening into parotid papilla opp 2nd upper molar
•
Secretomotor fibres to submandibular & sublingual gland:
- Preganglionic fibres: CN VII via chorda tympani, travelling along lingual nerve
- Postganglionc fibres: Direct branches fr submandibular ganglion
!
NIGEL FONG 2011/2012
PAGE A320
M1 NOTES IN GROSS ANATOMY
!
8 | BRAIN, HEAD & NECK
CRANIAL N
FIBRE
SUPPLY
1º NEURON
2º NEURON
XII
Som Mot
Musc of tongue (intrinsic,
extrinsic) exc palatoglossus
Hypoglossal nuc.
-
Hypoglossal
Hypoglossal nerve (CN XII)
•
•
SS muscles of ipsilateral tongue except palatoglossus
LMN rootlets emerge fr hypoglossal nuc (medulla)
-
•
•
Leaves skull through hypoglossal canal and descend
to below angle of mandible
- Crosses ext carotid art, curves ant to appear below
the jaw (inf to lingual, superficial to hyoglossus)
LMN lesion: tongue deviates to side of lesion as other
side protrudes normally
UMN lesion: tongue deviates to side opposite lesion
- Bilat UMN influence but contralateral is dominant
!
!
F. PALATE
!
Bone & mucosa of palate
•
•
•
Forms roof of mouth & floor of nose
Hard palate: ant 2/3 - palatine process of maxillae & horizontal part, palatine bones
- mucosa firmly bound to underlying bone (submucous injections painful)
Soft palate: fibromuscular pos 1/3, formed by palatine aponeurosis and muscles,
attached to pos border of hard palate
- Laterally cont w wall of pharynx, joined to tongue & pharynx by palatoglossal &
palatopharyngeal arches
- Uvula hangs from pos soft palate
!
NIGEL FONG 2011/2012
PAGE A321
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
Muscles of soft palate
•
•
May elevate palate pos/sup against wall of pharynx, or depress it to contact pos tongue
- Elevation ensures that food does not pass into the nasopharynx during swallowing
May tense soft palate so tongue may push against it, squeezing food bolus backwards
!
MUSCLE
Tensor veli palatini
NERVE
CN V3
Levator veli palatini
Palatoglossus
Palatopharyngeus
Musculus uvulae
ORIGIN
Hooks around pterygoid
hamulus
Auditory tube cartilage
CN X via
pharyngeal
plexus
INSERTION
Side of tongue
ACTION
Tenses soft palate
Palatine
aponeurosis
Elevates soft palate
Pull tongue up/back
Lat wall pharynx
Elevates larynx dur
swallowing
Uvula
Shortens uvula
!
Neurovasculature
•
•
•
From maxillary artery, to pterygoid venous plexus
- Greater & lesser palatine art (via greater / lesser palatine foramina in hard palate)
Sensory innervation from CN V2
- Nasopalatine nerve (via incisive canal): to ant hard palate
- Greater palatine nerves (via greater palatine foramina): to ant hard palate
- Lesser palatine nerves (via lesser palatine foramina): to soft palate, palatine tonsil
CN IX also contributes to sensory ss to pos soft palate
!
NIGEL FONG 2011/2012
PAGE A322
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!!!!!!!!
!
!
!
Development of palate
•
Face forms from 1st pharyngeal arch (end of week 4)
- Splits into 1 frontonasal, 2 maxillary, and 2 mandibular prominences
- Maxillary & mandibular prominence separated by stomodeum, which forms mouth
- Nasal pits demarcate med & lat nasal prominence on either side
Maxillary prominences grow medially, join median nasal promimence
•
- Gives lateral portion of upper lip
Medial nasal prominences fuse to form intermaxillary segment
•
- Gives philtrium of upper lip, upper jaw & 4 incisors, primary palate
Palatine shelves (palatal processes) grow from the maxillary prominence
•
- Forms secondary palate (fuses with primary palate at the incisive foramen)
- Soft palate grows from pos edge of palatal processes
R/L mandibular processes fuse to form the mandible
•
Cleft lip & palate
•
•
•
•
Result in abnormal facial appearance, difficulty speaking & eating (unable to suck
efficiently, food is regurgigated through nose or aspirated into lungs)
Failure of maxillary prominence to fuse w medial nasal prominence [B-D]
- Lat cleft lip, cleft upper jaw, cleft btw 1º and 2º palates.
Failure of palatine shelves to fuse [E]
- Cleft (secondary) palate, cleft uvula
Median cleft lip due to failure of medial nasal prominence to merge is rare.
!
!!
NIGEL FONG 2011/2012
!!
!
PAGE A323
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
9. PHARYNX & LARYNX
A. PHARYNX
!
Divisions of pharynx
•
•
!
Nasopharynx: pos to nose, fr base of skull to soft palate
Oropharynx: pos to mouth, fr soft palate to epiglottis
- transmits air
- transmit food & air
•
Laryngopharynx: pos to larynx, fr epiglottis to cricoid
•
Relations
- Sup: body of sphenoid (and sinus)
- Pos: Retropharyngeal space, lymph nodes, prevertebral muscles, spine
- Lat: carotid sheath (w ICA, IJV, lymph nodes), CN IX-XII, parotid
- transmit food
Eustachian (auditory, pharyngotympanic) tube
•
•
Connects nasopharynx to tympanic cavity, allows
equalization of pressure in middle ear (on either
side of tympanic membrane)
Cartilaginous part opens into nasopharynx
-
•
•
Normally closed until opened when yawning /
swallowing (action of tensor & levator veli
palatini, attached to it)
Bony part lies within petrous temporal bone,
opens into tympanic cavity (ant wall middle ear)
Clinical: when tube is blocked (e.g. infection), air
in tympanic cavity is abs by vessels. The lower
pressure inside the tympanic cavity pulls the
tympanic membrane inwards, affecting hearing.
- More horizontal in children: easier spread of
infections from nose
NIGEL FONG 2011/2012
!
PAGE A324
M1 NOTES IN GROSS ANATOMY
Nasopharynx
8 | BRAIN, HEAD & NECK
!!
•
•
Opens from nasal cavity through 2 chonae
Pharyngeal tonsil (adenoids): lymphoid tissue in roof /pos wall of nasopharynx
•
Clinical: Adenoiditis can obstruct passage of air, block pharyngotympanic tubes,
impair hearing, and infection spread to ear causing otitis media, hearing loss etc
Salpingopharyngeal fold formed by salpingopharyngeus muscle
•
•
Pharyngotympanic (auditory, eustachian) tube opens into lat wall of nasopharynx
Pharyngeal recess : lat ext of wall of nasopharynx
-
-
Clinical: Common site of nasopharyngeal cancer
Oropharynx (C2-3 level)
•
•
•
Opens from oral cavity thru oropharyngeal
isthmus (formed by palatoglossal folds, soft
palate, tongue)
Palatine tonsils lie lat in tonsilar fossa, btw
palatoglossal & palatopharyngeal arches
Vallacula ant to epiglottis forms a food trap
!
!
Laryngopharynx
•
•
Communicates with larynx through laryngeal inlet on ant wall
- Piriform recess on either side of laryngeal inlet form a food trap
Clinical: Closely related to sup laryngeal n (& int laryngeal branch), may be damaged
by foreign objects or their removal
NIGEL FONG 2011/2012
PAGE A325
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
Muscles of pharynx
•
•
Like arrangement of GIT: outer circular (3) and inner longitudinal (3) muscles
- Peristaltic movements + sphincteric function of inf constrictor
Pharyngobasilar fascia lies between layers, forming pos wall of pharynx
- - Gap btw sup & middle constrictors: stylopharyngeus, CN XII pass
!
MUSCLE
Sup constrictor
Middle constrictor
Inf constrictor
Palatopharyngeus
Salpingopharyngeus
Stylopharyngeus
NERVE
CN X
via
pharyngeal
plexus
CN IX
ORIGIN
INSERTION
ACTION
Interdigitate
Peristalsis
Wall of
pharynx
Elevate pharynx
to receive food or
speak
Joins buccinator and bone
Hyoid bone
Thyroid & cricoid cartilage
Soft palate
Auditory tube
Styloid process
!
!
NIGEL FONG 2011/2012
!!
!
PAGE A326
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
Swallowing (deglutition)
PHASE
PROCESS
MUSCLES
NERVE
Oral
(voluntary)
Bolus of food compressed against palate &
pushed into oropharynx
Styloglossus, palatoglossus
CN IX,
CN X
Pharyngeal
(involuntary)
Soft palate elvates to shut off nasopharynx
Larynx elevates & inlet closes
Pharyngeal & laryngeal
muscles
CN X
Esophageal
(involuntary)
Bolus moves downward over epiglottis, forced
down laryngopharynx into esophagus
Pharyngeal constrictors
CN X
!
!
!
Pharyngeal plexus
•
Pharyngeal plexus forms on surf of pharyngeal constrictors
•
Motor ss of pharynx & soft palate by CN X
- except stylopharyngeus (CN IX) & tensor veli palatini (CN V3)
Sensory: from CN IX
Gag reflex: touching back of tongue results in reflex contraction of pharynx to
prevent abnormal items entering throat.
•
•
Vasculature
•
•
Blood supply: mainly by ascending pharyngeal branch of ext carotid art
- Small branches of facial & maxillary art, sup/inf thyroid art
Lymphatic drainage: into deep cervical nodes
- May via pharyngeal lymphatic (tonsilar) ring: palatine, lingual, pharyngeal tonsils
!
!
NIGEL FONG 2011/2012
!
PAGE A327
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
B. LARYNX
!
Skeleton of larynx
•
•
Thyroid cartilage: large paired laminae which fuse anteriorly to give laryngeal
prominence (Adam’s apple)
Cricoid cartilage: signet ring shape, taller pos
-
•
Articulates w inf horn of thyroid cartilage (cricothyroid jt) – allows thyroid
cartilage to swivel fwd
Arytenoid cartilage: paired, can rotate, slide twds/away, tilt ant/pos
•
- Cricoarytenoid joint: articulates w sup edge cricoid cartilage
- Vocal process: for attachment of vocal ligament / vocalis muscles
- Muscular process: a lever on which lat & pos cricoarytenoid muscles attach
- Related to small corniculate & cuneiform cartilages.
Epiglottic cartilage: Leaf shaped elastic cartilage, ant to & closes laryngeal inlet
-
Lies pos to root of tongue, stalk attached to pos surf of thyroid cartilage
!
Vocal folds
•
•
Larynx cont. fr laryngopharynx at the laryngeal inlet, and cont as the trachea at C6
- Divided into vestibule (sup) and infraglottic cavity (inf) by the vocal folds
Vestibular fold (false vocal cord) sup to true vocal cord has a protective function
-
•
Laryngeal ventricle (sinus) ext lat btw false/true folds, w glands to lubricate them
Vocal fold (true vocal cord) closes to prevent entry of food, and vibrates to prod voice
-
Formed by vocal ligaments which extend fr pos surface of lamina of thyroid
cartilage to vocal process of arytenoid
!
NIGEL FONG 2011/2012
!
PAGE A328
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Laryngoscopic view
•
Folds visible, from superior to inf
- Ary-epiglottic folds in vestibule
-
•
Vestibular fold with an aperture in
between, the rima vestibuli
Vocal fold with rima glottis btw
Epiglottis attached to base of tongue by
med & 2 lat glossoepiglotic folds
Food can get stuck in the vallecula,
between the folds
Food also can get stuck in the piriform
recess on either side of larynx
-
•
!
Movements of vocal fold & muscles of larynx
•
•
•
Swallowing: most muscles
- Laryngeal inlet closed
- Ary-epiglottic folds adducted, larynx pulled up
twd epiglottis to prevent food entering trachea
Breathing: Pos cricoarytenoid abducts vocal folds
Phonation: Lat cricoarytenoid (and others) abduct
vocal folds so that they are closely apposed / slit like
- ↑ Voice pitch: ↑ vocal fold tension (cricothyroid),
- ↓ Pitch: ↓ tension (thyro-arytenoid, vocalis).
- In postpubertal males, vocal folds are longer,
hence voice is lower-pitched
!
!
MUSCLE
NERVE
Pos crico-arytenoid
Lat crico-arytenoid
Transverse & oblique
arytenoid
Thyro-epiglottic
CN X via
recurrent
laryngeal n
Thyro-arytenoid & Vocalis
Cricothyroid
ORIGIN
INSERTION
ACTION
Cricoid
Muscular process,
arytenoid cartilage
Abduct
Arytenoid
Contralateral arytenoid
Adduct &
close inlet
Thyroid c
Epiglottic cartilage
Opens inlet
Lat to vocal ligament
CN X via ext
laryngeal
Ant surf cricoid
Ant surf thyroid c
Relax
Tenses, tilt
thyroid fwd
!!
NIGEL FONG 2011/2012
PAGE A329
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Blood supply
•
Sup laryngeal art
-
•
Fr ext carotid via superior
thyroid art (travels w int
laryngeal n)
Inf laryngeal art
-
•
•
Fr subclavian via inf thyroid
art (w inf laryngeal n)
Veins: sup/inf laryngeal veins
accompanying the arteries
Lymphatic drainage: to deep
cervical lymph nodes, possibly
via pretracheal nodes
!
Nerve supply
•
•
Supply: all from CN X
- Motor: All by inferior laryngeal except cricothyroid, which is fr ext laryngeal
- Sensory: Int laryngeal above vocal folds, inf laryngeal below vocal folds
Superior laryngeal n fr CN X at inf vagal ganglion
-
External laryngeal n: descends adj to sup thyroid art
Internal laryngeal n: pierces thyrohyoid membrane to enter mucosa
Clinical: sup laryngeal n block e.g. endotracheal intubation: insert needle midway
btw thyroid & hyoid.
Recurrent laryngeal n loops ard arch of aorta (LHS) / subclavian (RHS), ascending
in the tracheo-esophageal groove as inf laryngeal nerve (close to inf thyroid art)
-
•
•
Clinical: Injury to these nerves result in hoarseness of voice
- Recurrent laryngeal n injury (vulnerable due to long course) – all muscles except
cricothyroid affected. In crush injury, abductors affected more than adductors
- External laryngeal n injury – cricothyroid affected
- Internal laryngeal n injury – loss of sensation, protective mechanism to keep foreign
bodies out is inactive, foreign bodies enter easily
!!!!!!!!!!
NIGEL FONG 2011/2012
PAGE A330
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
C. CRANIAL NERVES IX & X
!
CRANIAL N
IX
X
Glossopharyngeal
Vagus
FIBRE
SUPPLY
1º NEURON
2º NEURON
Spec Sen
Taste: Pos 1/3 of tongue
Vis Sen
Baroreception: carotid sinus
Glossopharyngeal
ganglion (inf)
Nucleus tractus
solitarius
Som Sen
Pos 1/3 tongue, Pharynx,
Ext & middle ear
Glossopharyngeal
ganglion (sup)
Spinal nuc of V
Som Mot
Stylopharyngeus
Nuc Ambiguus
-
Spec Sen
Taste: Palate, epiglottis
Vis Sen
Heart, Resp, GIT up to
midgut
Vagal ganglion
(inf)
Nucleus tractus
solitarius
Som Sen
Ext ear, Larynx
Vagal gang. (sup)
Spinal nuc of V
Parasym
CVS, Resp, GIT up to
midgut
Dorsal motor nuc
Various
Som Mot
Musc of soft palate (exc
tensor palatini), pharynx
(exc stylopharyngeus),
larynx, sup 2/3 esophagus
Nuc Ambiguus
-
!
Course of CN IX
•
•
•
•
Emerges from lat medulla
- Gives tympanic branch to ear
- Gives lesser petrosal nerve (parasympathetic to parotid, via otic ganglion)
Leaves cranium through jugular foramen (together with CN X & XI)
- Site of sup & inf glossopharyngeal ganglia (sensory, pseudo-unipolar neurons)
Descends pos to stylopharyngeus (supplying it)
- Carotid branch to carotid sinus & carotid body
Enters mouth btw sup & mid pharyngeal constrictors, contributes to pharyngeal plexus
!
NIGEL FONG 2011/2012
PAGE A331
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Course of CN X
•
•
•
!
Arises as series of rootlets from lateral medulla
- Cranial root of accessory nerve joins Vagus and is distributed together
Leaves cranium through jugular foramen (together with CN IX & XI)
- Site of sup & inf vagal ganglia (sensory, pseudo-unipolar neurons)
Continues in carotid sheath to root of neck, descending down the esophagus into the
thorax and abdomen, supplying as far as proximal 2/3 of transverse colon
Sensory pathway
MODALITY
1º NEURON
2º NEURON
3º NEURON
Somatic Sensory
Sup IX / X ganglia
Spinal nucleus of V
Contralat thalamus
Ipsilateral nuc solitarius
Ipsilat thalamus
Brainstem reticular n
-
Taste
Visceral Sensory
!
Inf IX / X ganglia
Then to
cortex
Effect of lesion
•
•
•
CN IX-XI may be affected together e.g. fracture of base of skull at jugular foramen
LMN lesion of CN IX / X
- Dysarthria (difficulty speaking) & dysphagia (difficulty swallowing)
- Ipsilateral loss of gag reflex (requires motor & sensory)
- Bilateral lesion of CN X not compatible with life
UMN lesion: little effect because of bilateral cortical control
NIGEL FONG 2011/2012
PAGE A332
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
10. EAR & HEARING
!
A. EXTERNAL EAR
!
External ear
•
•
•
•
Auricle: Assists in collecting sound
- Elastic cartilage covered by thin skin
External acoustic meatus: conducts sound from
auricle to tympanic membrane
- Outer 2/3 bony, inner 1/3 cartilaginous
- Lined by skin which secretes earwax
Clinical: external ear is not straight. to straighten,
pull up and backwards.
Sensory SS of ext ear & outer surface tympanic mem
- CN V3 (auriculotemporal), C2-3
- Minor contributions fr CN X, CN VII
!
!
Tympanic membrane
•
•
•
•
Divides external & middle ear
Normally translucent & pearly grey (on otoscopic examination)
- Clinical: Bulging red tympanic membrane may indicate otitis media (infection of
middle ear), often secondary to upper respiratory infection blocking eustachian tube
Transfers sound vibrations from air to auditory ossicles
- Clinical: ruptured eardrum - perforation of tympanic membrane may result from
otits media, foreign bodies, trauma, excessive pressure, and can cause deafness.
Sensory supply: outer part follows ext ear, inner part follows inner ear
Normal otoscopic view:
Otitis media:
!
!
NIGEL FONG 2011/2012
PAGE A333
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
B. MIDDLE EAR
Middle ear (tympanic cavity)
•
•
Air-filled chamber in petrous part of temporal bone
Ossicles form mobile chain to transmit sound fr tympanic mem to inner ear.
-
•
Consist of malleus (hammer), incus (anvil), stapes (stirrup)
- Handle of malleus attached to tympanic mem, base of stapes fills oval window
Vibration dampening to soften loud sounds occurs via reflex contractions of muscles
- Stapedius: attached to and dampens stapes (supplied by CN VII)
-
Tensor tympani: attached to and dampens malleus (supplied CN V3)
Walls & relations of middle ear
•
•
•
•
•
•
Lat wall : Tympanic membrane, chorda tympani nerve (deep to mem)
Med wall : Promontory formed by 1st turn of cochlea, covered by tympanic plexus
: Oval window & round window
: Prominence of facial canal containing CN VII
Pos wall : Aditus, communicating with mastoid sinus
Ant wall :
:
Floor
:
Roof
:
Opening of eustachian (auditory, pharyngotympanic) tube to nasopharynx
Related to int carotid artery
Related to int jugular vein
Epitympanic recess, related to middle cranial fossa / temporal lobe
!
NIGEL FONG 2011/2012
PAGE A334
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
Nerves in the middle ear
•
•
!
CN IX: Tympanic nerve / branch
- Forms tympanic plexus: somatic sensory to ear
- Gives lesser petrosal n: parasympathetic to parotid
Facial nerve: lies in facial canal
- Gives n to stapedius, greater petrosal n & chorda tympani (see CN VII)
Clinical notes
•
•
•
Otitis media, blockage of pharyngotympanic tube
Mastoiditis: Otitis media may spread to mastoid air cells.
- Can spread sup to middle cranial fissure
- During surgical treatment, care has to be taken not to injure CN VII
Hyperacusis (intolerance of loud sounds) may result from paralysis of stapedius due
to facial nerve lesion (see facial nerve)
C. INNER EAR
!
!!!
!
Component parts
•
•
Located in petrous part of temporal bone, btw middle & pos cranial fossa
Vestibular system: innervated by vestibular nerve from CN VIII
- Utricle & Saccule: sense static head position
-
•
Semicircular canals (in 3 different axis): sense head rotation
Cochlea: organ of hearing, innervated by cochlear nerve from CN VIII
-
Consists of perilymph-filled scala vestibuli (inside/upper) and scala tympani,
which communicate at the helicotrema
Scala media (cochlear duct) w endolymph separates the scala vestibuli & tympani
Basilar membrane: partition between scala media & scala tympani
!
NIGEL FONG 2011/2012
PAGE A335
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
!
Transmission of sound through the cochlea
•
•
•
At the oval window, vibrations of the auditory ossicles are transduced into pressure
waves in the perilymph of the scala vestibuli
Pressure wave ascends through scala vestibuli to cochlear apex, goes round helicotrema,
returns via scala tympani to basal turn of cochlea.
Pressure wave arrives at the round window; membrane closing round window bulges
outward, dissipating the pressure wave
Sound analysis
•
•
•
•
Properties of basilar membrane varies along its
length: tuned to progression of frequencies
- Base of cochlea: thick & taut, resonates in
response to ↑ frequency (20 kHz)
- Apex of cochlea: thin & floppy, resonates in
response to ↓ frequency (20 Hz)
Organ of corti: on basilar membrane, carried
along when basilar membrane vibrates
- 1 row inner hair cells, 3 rows outer hair cells
When basilar mem vibrates, inner hair cells
vibrate, creating an action potential.
- Tonotropic arrangement: every hair cell
most sensitive to stimu of specific frequency
Outer hair cells amplify sound: contract in
response to movement of basilar membrane,
exacerbating vibrations picked up by inner c
- Clinical: Otoacoustic emissions: through this
mechanism, sound can be produced and
detected from outside the ear. This is used
to test for hearing defects in infants.
!
!
!
!
!
NIGEL FONG 2011/2012
PAGE A336
M1 NOTES IN GROSS ANATOMY
8 | BRAIN, HEAD & NECK
D. CRANIAL NERVE VIII & HEARING PATHWAY
!
CRANIAL N
VIII
Vestibulocochlear
FIBRE
Spec Sen
SUPPLY
1º NEURON
2º NEURON
Vestibular sense, balance
Vestibular gang.
Vestibular nuc
Hearing: spiral organ
Spiral gang
Cochlear nuc
!
Vestibular nerve
•
•
•
•
•
•
1º
2º
neurons receive information from:
Static labyrinth (utricle & saccule): info about head position in space
Kinetic labyrinth (semicircular canals): info about rotational movements
Cell body in spiral vestibular ganglion
neuron in vestibular nucleus: 4-part nucleus in dorsolateral pons/medulla
- Some 2º neurons in cerebellum
Projects to ocular motor nuclei, allowing Vestibular-ocular reflex: compensatory
movements of extra-ocular muscles to maintain gaze even as head is moved
Projects to spinal cord, forming vestibulospinal tract
- Supply extensor muscles, adjusting posture to maintain balance
Clinical: Defect in vestibular system results in vertigo (dizziness) and nystagmus
(involuntary eye movements)
Clinical: Motion sickness results from discordance btw visual & vestibular stimulation
Cochlear nerve & hearing pathway
•
•
•
1º neurons receive sensory info from inner hair cells at basilar membrane of cochlea
(high pitch from basal turn, low pitch from apex)
- Cell body in spiral ganglion
2º neuron in cochlear nucleus at ponto-medullary
junction
Multistep bilateral pathway (cross + uncross)
- To bilat sup olivary nucleus: localize sounds
by comparing time of arrival & intensity
- To inf colliculus
- To thalamus, medial geniculate nucleus (vs
vision: lateral geniculate nucleus)
- To 1º auditory cortex (temporal lobe, sup
temporal gyrus inf to lat fissure)
- To auditory association cortex (Wernicke’s
speech area) – see cortex
!
!
Hearing loss
•
•
Conductive hearing loss: interference with mechanical conduction of sound by air to
tympanic membrane, by ossicle bones to cochlea
Sensineural hearing loss: defects in spiral organ, cochlear nerve, hearing pathway
-
•
High frequency hearing loss: deterioriation of basal turn of organ of corti
Cochlear inplants: small ext microphone recv sounds and transmits this to an
implated receiver. Receiver sends electrical impulses to cochlea, stim. cochlear nerve
Stimulation of 1º sensory cortex: tinnitus (buzzing, humming, ringing)
NIGEL FONG 2011/2012
PAGE A337