ILM 1 – Nervous System
1) Describe the basic organization of the nervous system.
a. See written notes for web
2) Describe the relationship between spinal cord segments and vertebral levels
and how this relationship changes during development.
• 7 cervical vertebrae à 8 pairs of cervical spinal nerves (8
pairs because first pair of cervical spinal nerves exits
above C1 vertebrae)
o Cervical segment is only segment of SC where the
nerves move above their corresponding vertebrae
• 12 thoracic vertebrae à 12 pairs of thoracic spinal nerves
• 5 lumbar vertebrae à 5 pairs of lumbar spinal nerves
• 5 sacral vertebrae à 5 pairs of sacral spinal nerves
• 1 coccyx à 1 pair of coccygeal spinal nerves
-Early in development, spinal nerves and spinal segments lie in
close proximity
-BUT spinal cord grows slower than vertebral column
-This disconnect is more pronounced as you move
inferiorly
-Actual SC ends around L1/L2
-Ex: Sacral nerves actually around L1/L2
3) Recognize the segmental organization of the human body and state the definition of a
dermatome and myotome.
• Dermatome – area of skin supplied by a single spinal nerve
• Myotome – mass of muscle supplied by a single spinal nerve
**Netter plate 171
4) Discuss the structure of a typical spinal nerve and its distribution.
•
Any given spinal/cranial nerve contains multiple bundles of nerve fibers à this means
they can carry sensory fibers, motor fibers, or both
5) Compare the pathways of somatic motor and somatic sensory neurons.
*See pathways comparison pages in written notes
6) Compare the pathways of the sympathetic and parasympathetic nervous
systems.
*See pathways comparison pages in written notes
7) Describe the phenomenon of referred pain.
• Referred pain – phenomenon of visceral (organ) pain perceived as somatic (body wall)
pain
o Occurs because the dorsal root ganglion houses cell bodies of both visceral
sensory and somatic sensory neurons
§ Ex: ischemia of heart muscle perceived by CNS as body wall pain
(shoulder/L arm)
• CNS misinterprets incoming visceral sensory signal as somatic
8) Predict the deficits that would result if a ventral root, dorsal root, spinal nerve, ventral
ramus, dorsal ramus, white ramus communicans or gray ramus communicans is injured.
ILM 2 – Thoracic Wall
1) Identify the thoracic vertebrae (body, transverse processes, spinous process, costal
facets), ribs (head, tubercle, body, angle, costal groove), costal cartilages, sternum
(manubrium, body, xiphoid process) and clavicles.
Thoracic skeleton:
-12 thoracic vertebrae
Thoracic vertebrae anatomy:
Rib anatomy:
Atypical Ribs – ribs that lack some feature of typical ribs (seen above)
-Rib 1 – two depressions on superior surface for subclavian artery & vein (which runs
between clavicle and rib 1)
-Ribs 11 & 12 – short ribs without tubercles and angles
Other Rib Classifications:
• True Ribs – attach to sternum with their own costal cartilage (1-7)
• False Ribs – attach to sternum indirectly via costal cartilage of rib above it (8-10)
• Floating Ribs – do not attach to sternum; imbedded in musculature of thoracic wall (1112)
Costal Cartilages – connect ribs to sternum (hyaline
cartilage) at sternocostal joints (most are synovial to permit
movement)
Sternal Anatomy:
Manubrium – articulates with ribs 1 & 2 and
with body of sternum (at an angle ~T4/5 à
sternal angle)
Body – articulates with costal cartilages of ribs
2-7
Xiphoid process – inferior tip of sternum; may
ossify and fuse with body of sternum in
adulthood; found around T10 vertebral level
2) Locate the jugular notch, sternal angle, and costal margin.
• Jugular (suprasternal) notch – located at top of manubrium
• Sternal angle – located around T4/T5; landmark for bifurcation of trachea
• Costal margin – ribs 7-10 (see image above)
3) Describe the segmental organization of the body, including the nerves and vessels of
the thoracic wall. Define the dermatome and myotome levels present on the thoracic
wall. Describe the course and branches of a typical spinal nerve, segmental artery and
vein in an intercostal space (e.g., relative to ribs and muscle layers).
• Intercostal Neurovascular Bundles – intercostal vein, artery, and
nerve (“VAN”)
o Lie between the INTERNAL and INNERMOST intercostal
muscles (in the costal groove)
§ Collateral branches extend inferiorly at the angle of
the rib (lie alone superior edge of rib below)
o Intercostal nerves are the ventral rami of T1-T11 spinal
nerves à supply lateral and anterior aspects of
thoracic wall
§ 11 intercostal spaces = 11 intercostal nerves
• BUT?? 12 ribs and 12 thoracic spinal
nerves??
o T12 ventral ramus travels below
T12 à “Subcostal nerve”
o Types of fibers present in intercostal nerves:
§ Somatic Motor
• To skeletal muscles à intercostal muscles
§ Somatic Sensory
• From skin à pain, temperature, touch
• From joints
• From skeletal muscles
• From tendons
• In general: Proprioception
§ Sympathetic Fibers
• To skin à sweat glands, arrector pili muscles, and blood
vessels
•
•
Dermatomes – areas of skin innervated by specific spinal nerves
https://www.picmonic.com/learn/dermatomes-thoracic_1498
o Thoracic: T1-T12
§ T1 – medial arm
§ T4 – nipple
§ T7 – xiphoid
§ T10 – belly button
§ T12 – pubis
Thoracic Wall Blood Supply
o Thoracic Aorta – primary supply; anterior to
spinal column
§ Gives off posterior intercostal
arteries
• PIAs give off collateral branches @ angles of ribs (basically
just name change as it angles posteriorly)
o Internal Thoracic (Mammary) Arteries – paired L/R; branches of
subclavian arteries
§ Anteriorly deep to rib cage, run parallel to sternum (located on
anterior thoracic wall)
§ Give off anterior intercostal arteries (2 per
intercostal space)
§ Because of location close to the heart,
commonly used in CABG
**Posterior intercostal arteries & their collateral branches
anastamose with anterior intercostal arteries à means
they are connected structures and blood can travel in
either direction à connection VERY IMPORTANT in case of a blockage (esp of
internal thoracic artery)
•
Intercostal Veins
o Posterior intercostal veins drain into azygous venous
system à superior vena cava à back to heart
o Anterior intercostal veins drain into internal thoracic
veins à brachiocephalic vein à superior vena cava
4) Use your knowledge of the contents of an intercostal space to perform
an intercostal nerve block.
5) Describe the innervation of sweat glands, arrector pili muscles, and blood vessels in
the skin.
• Sympathetic (see pathways written notes)
6) Predict the deficits that will result if an intercostal nerve is injured.
• Know dermatomes and types of innervations by intercostal nerves
ILM 3 – Innervation of Thoracic and Abdominal Organs
1) Compare and contrast the parasympathetic innervation of the lungs, heart, foregut,
midgut, and hindgut.
• See written pathways
2) Compare and contrast the sympathetic innervation of the lungs, heart, foregut,
midgut, and hindgut.
• See written pathways
3) Indicate the regions on the body wall to which cardiac pain can refer.
• T1, C4-C8 **DERMATOMES
• Neck, chest, shoulders, arms/forearms, upper abdomen
4) Indicate the regions on the body wall to which foregut, midgut, and hindgut pain
typically refer. Describe the presentation of pain that is associated with appendicitis.
• Foregut – area at and inferior to costal margin
• Midgut & Hindgut – more inferior locations on anterior abdominal wall
o Ex: appendicitis
§ Pain typically presents as diffuse pain around umbilicus (T10
dermatome)
§ But as parietal peritoneum becomes inflamed, somatic sensory
innervation of the parietal peritoneum will localize pain to RLQ
• This area is known as McBurney’s Point – the area of
tenderness in cases of appendicitis
ILM 4 – Lungs and Diaphragm
1) Distinguish between the parietal and visceral pleurae and describe their innervation.
• Visceral Pleura – lines surfaces of the lung; closely adheres to lungs, lines lung
fissures
o Innervation:
§ Visceral Sensory à ischemia, stretch
§ NO somatic sensory innervation (pain/temp/touch)
• Parietal Pleura – lines walls of thoracic cavity, diaphragm, and mediastinum
o Innervation:
§ Somatic Sensory à sensitive to pain/temp/touch
• Travels back to CNS via intercostal nerves and phrenic
nerve
-Both are continuous from one another (*balloon/fist analogy); serous sacs filled
with fluid
-Pleuritis – inflammation of pleura à can lead to adhesion of visceral/parietal
layers
-Results in acute pain with elevated activity
2) Define the pleural cavity and costodiaphragmatic recesses.
• Pleural Cavity – “potential space” between outer parietal/ inner visceral pleurae
o R/L pleural cavities are independent of one another
o Normally contains a very thin layer of serous fluid, which allows the two
layers to slide against one another during respiration
• Costodiaphragmatic Recesses – inferior/lateral parts of pleural cavities
o With inspiration (*especially forced), lungs expand into this, causing the
recess to decrease in area
o With expiration, these recesses enlarge again
•
Clinical Correlations:
o Potential spaces of pleural cavities can become filled with fluid/air/blood
due to illness or injury
§ Hydrothorax – FLUID in pleural cavity à result of pleural effusion
due to blocked lymph vessels, infection, lung injury, tumors
§ Hemothorax – BLOOD in pleural cavity à result of injury to
intercostal vessels or internal thoracic vessels
§ Pneumothorax – AIR in pleural cavity à result of puncture wound
that penetrates parietal pleura
• Lungs possess elasticity (allowing them to recoil to ~1/3 of
their original size), which collapses in case of
pneumothorax
•
•
L side is more opaque and can see vasculature
R lung is hyperlucent (cannot see vascular structures) à indicates R collapsed
lung
3) Apply your knowledge of the costodiaphragmatic recesses to perform thoracentesis.
• In an x-ray, costodiaphragmatic recess should appear as a sharp/acute angle
formed by lateral thoracic wall + lateral aspect of diaphragm
•
In the image on the right, the right side of patient shows a rounded
costodiaphragmatic recess (no acute angle)
o Indicates a potential hydrothorax or hemothorax
• If there is fluid in the pleural cavity, a thoracentesis will be performed
o Thoracentesis Steps:
§ Intercostal nerve block performed
§ Needle inserted into intercostal space, avoiding intercostal nerve
bundles
§ ***Posterior aspect of 7-9th intercostal spaces are usually safe
spaces for these
§ As needle enters costodiaphragmatic recess, avoid injury to lungs
and nearby abdominal organs
4) Contrast the structure of the right and left lungs (e.g., number of lobes, fissures).
• Right lung à 3 lobes
o Superior, middle, and inferior lobe
§ Separated by 2 fissures
• R horizontal fissure
o Separates superior/middle lobes
•
•
R oblique fissure
o Separates middle/inferior lobes
o R lung is typically larger than left because the mediastinum (containing the
heart) bulges more into the L side of the body, which restricts size of L lung
Left lung à 2 lobes
o Superior and inferior lobe
§ Separated by oblique fissure
o Cardiac notch found on anterior border of superior lobe
§ Caused by the apex of the heart deviating to the left
5) Describe the trachea and bronchi. Explain the clinical significance of the structural
differences between the left and right main bronchi.
• Trachea – continuous with (superior) larynx
o Palpate at jugular notch
§ Will be palpating the wall of the trachea, which is fortified by Cshaped rings of hyaline cartilage
• Hyaline cartilage is incomplete posteriorly à closed off by
smooth muscle and mucosa
o Bifurcates at sternal angle (T4/T5 IV disk)
§ Carina – marks the bifurcation with ridge of cartilage (best seen from
internal view)
§ Bifurcation leads to R/L main bronchi
•
Bronchi – bifurcation of trachea leads to R/L bronchus (pl. bronchi)
o Bronchi are extrapulmonary (*exist outside of lung)
o Supported by c-shaped hyaline cartilage (like trachea)
o Right main bronchus is wider, shorter, and runs more vertically than the left
§ This asymmetry means aspirated foreign objects are more likely to lodge
in the R bronchus (because of its shape)
•
Bronchial Tree – right and left main bronchi divide into lobar bronchi
o Lobar bronchi are intrapulmonary
o 3 Right lobar bronchi
o 2 Left lobar bronchi
§ *Corresponds to 3 lobes of R lung, 2 lobes of L lung
o Lobar bronchi divide into segmental bronchi (*intrapulmonary)
§ Segmental bronchi supply bronchopulmonary segment (*see #7)
6) Distinguish between the pulmonary and bronchial arteries and veins.
• Pulmonary Arteries and Veins – carry oxygen poor/rich blood from/to the heart
o Pulmonary ARTERIES blood flow:
§ Oxygen poor blood from right ventricle à pulmonary trunk à R/L
pulmonary artery à lobar artery à segmental artery
§ **Pulmonary arteries follow same branching pattern as bronchial
tree; within lungs, bronchi and pulmonary aa are paired and
branch in unison
o Pulmonary VEINS
§ Oxygen rich blood from lungs à 2 pulmonary veins on each side
à L atrium
§ *intersegmental (running through connective tissue separating
bronchopulmonary lobar segments)
§ *Pulmonary veins do NOT branch following pulmonary
arteries/bronchi
•
Bronchial Arteries and Veins – supply and drain the lung tissue itself (including
bronchi/connective tissue to lungs
o Bronchial ARTERIES – carry oxygen rich blood to lung tissue
§ Most bronchial arteries are branches off of thoracic aorta
o Bronchial VEINS – return oxygen poor blood from lung tissues to azygous
system or to intercostal veins
§ Azygous system drains thoracic wall and upper lumbar region of
spinal cord via lumbar veins and posterior intercostal veins
7) Define a bronchopulmonary segment and discuss the clinical significance of these
segments.
• Bronchopulmonary Segments – subdivision of a lobe; 10 per lung
o Each supplied by: segmental bronchus and segmental branch of
pulmonary artery
o Clinical Significance:
§ Functionally independent separated by connective tissue (so can
be surgically resected if affected by disease)
o Pulmonary veins are intersegmental à they drain oxygen rich blood and
are found in connective tissue between these segments
8) Describe the attachments of the diaphragm and indicate where structures pass
through the diaphragm relative to one another and relative to the vertebrae.
• Diaphragm Attachments:
o Anteriorly à attaches to posterior aspect of xiphoid process
o Laterally à attaches to internal surface of costal margin
o Posteriorly à attaches to floating ribs 11-12, lumbar vertebrae (through
R & L crura)
§ Crura – musculotendinous bands that arise from anterior surfaces
of bodies of lumbar vertebrae)
• The diaphragm separates the thoracic and abdominal cavities, but some
structures are continuous between the two areas, so the diaphragm has 3
apertures/openings:
o 1) Caval Opening – opening in central tendon primarily for inferior vena
cava
§ Lies at T8 vertebral level
§ *Most superior of the 3 openings
o 2) Esophageal Hiatus – opening for esophagus and vagus nerve
§ T10 vertebral level
o 3) Aortic Hiatus – opening for descending aorta, thoracic duct, and
azygous vein
§ T12 vertebral level
•
Diaphragm Innervation:
o Somatic SENSORY
§ Mostly through PHRENIC nerves
§ Peripherally through intercostal nerves
o Somatic MOTOR
§ From R/L phrenic nerves
• These phrenic nerves arise from ventral rami of C3, C4, and C5
o “C3, 4, & 5 keep diaphragm alive”
• L/R phrenic nerves innervate L/R domes independently
9) Describe the spinal levels of origin of the phrenic nerve, its course through the
mediastinum, and its primary functions.
• Originates in ventral rami of C3, C4, & C5
o *See above
• Phrenic nerve usually runs posterior to the subclavian vein as it enters the
thorax, where it runs anterior to the root of the lung and between the fibrous
pericardium and mediastinum parietal pleura
• Function: Motor innervation to diaphragm, works in conjunction with secondary
respiratory muscles to allow inspiration
o DIAPHRAGM is the PRIMARY muscle of INSPIRATION
10) Explain the movements of the thoracic wall and diaphragm during inspiration and
expiration.
• Movement of diaphragm:
o When it is relaxed you can see the 2 domes
o Domes pull inferiorly when contracted (breathing in)
§ As it flattens, it pulls abdominal viscera inferiorly (*flattens
DOWN) à this increases vertical dimensions of thoracic cavity
o What happens with a lesion of a phrenic nerve???
§ Side with damaged phrenic nerve will not move inferiorly
§ X-ray during inspiration will show a DEPRESSED ACTIVE side &
RAISED PARALYZED side
§ Image below shows paralyzed LEFT side
• Right is flattened during inspiration à NORMAL
• Left did not move/appears raised à L phrenic damaged
•
Movement of Thorax:
o *First, understand basics of respiration:
§ Air moves from H à L pressure
§ To draw air INTO lungs, thoracic pressure must be LESS than
atmospheric pressure
• Need to INCREASE volume of thoracic cavity
§ To expel air OUT of lungs, thoracic pressure must be MORE than
atmospheric pressure
• Need to DECREASE volume of thoracic cavity
o **How do we change volume of thoracic cavity??**
§ Contraction of muscles à ESPECIALLY diaphragm
§ CONTRACTION of diaphragm INCREASES vertical
dimension/volume of thorax
•
Intercostal muscles also help increase volume in thoracic cavity
o Medial/lateral dimension changes with elevation of ribs via intercostal
muscles
§ Ribs move like bucket handle
o Anterior/posterior dimension changes via intercostal muscles as they
move the sternum superiorly/anteriorly like a pump handle
•
Inspiration
o Forceful à pectoralis major recruited
§ Fixed upper limbs (like hands on hips) allows pec major to assist
with increasing the volume of thoracic cavity
Expiration
o Passive
§ Diaphragm, intercostal muscles, and others RELAX à decreases
intrathoracic volume à increases pressure
• Allows stretched elastic tissue of the lungs to recoil and
expel air
§ Concurrently, intraabdominal pressure decreases and abdominal
viscera are decompressed
§ Thoracic cavity size reduces (primarily due to relaxation of
diaphragm/elastic recoil of lungs) and thoracic pressure increases
o Forceful
§ Abdominal muscles like obliques and rectus abdominis are
recruited to compress abdominal viscera upward
•
•
This helps decrease volume of thoracic cavity/increase
pressure à allows air to leave from the HIGH internal
pressure to the LOW external pressure
ILM 5 – Mediastinum and Heart I
• Mediastinum – everything at the center of the thorax
o Extends entire anterior/posterior depth of thorax and entire length
(inferior/superior) (*but confined to midline area)
o Mediastinum Borders:
§ Superior – Superior Thoracic Aperture à big opening that connects the
thorax to the head/neck and upper limbs
• Borders of superior thoracic aperture
• 1st ribs (laterally)
• Manubrium (anteriorly)
• T1 vertebra (posteriorly)
§ Inferior – diaphragm
o Can be split into superior mediastinum and inferior mediastinum
§ Sternal angle is the separation point for superior/inferior (T4/T5)
1) Indicate the location of the thymus.
• Thymus crosses sternal angle (present above and below it)
o In adults, looks like fat
o Responsible for production of T cells à immunity!
2) Distinguish between the fibrous and serous pericardium, including the parietal and
visceral layers of the latter.
• Pericardium AKA pericardial sac
o Innervated by phrenic nerves (C3-5), which run anterior to root of lungs,
close to lateral aspect of pericardial sac
§ Phrenic Nerve Functions:
• MOTOR to diaphragm
• SENSORY to diaphragm, parietal pleura, fibrous
pericardium, parietal layer of serous pericardium
• 3 Pericardial layers:
o Fibrous à outermost layer
§ Tough, inelastic
• This limits pericardial expansion
•
Can become a problem if something starts filling
pericardial sac that shouldn’t be à cant expand OUT, so
will expand IN and compress heart
§ Attached inferiorly to central tendon of diaphragm à as
diaphragm contracts/relaxes, it pulls fibrous pericardium, which
pulls entire pericardium/heart superiorly & inferiorly
• Heart moves up & down with breathing!
o Serous à deep to fibrous; double layered continuous sac
§ 2 layers:
• Parietal
o Superficial, between fibrous and visceral
• Visceral (*Epicardium)
o Deep
o Applied directly to heart itself
§ Pericardial cavity= space between these two layers
3) Define the pericardial cavity. Relate the layers of pericardium to the phenomenon of
cardiac tamponade.
• Pericardial Cavity – potential space between parietal and visceral layers of
serous pericardium
o Filled with serous fluid
o Pericarditis à inflammation of pericardial cavity
• Cardiac Tamponade – accumulation of fluid in pericardial cavity
o Can compress the heart because the fibrous pericardium is inelastic and
restricts the expansion of the pericardium
• Pericardiocentesis à performed to remove fluid caused by cardiac tamponade
o 2 methods:
§ Sub-Xiphoid approach – feel xiphoid process, go slightly lateral
(between xiphoid and L costal margin) à put needle in just lateral
to xiphoid
§ Parasternal approach – go slightly lateral to sternal body in 5th/6th
intercostal spaces
§ **LEFT side of body because L lung and pleural cavity are smaller
4) Recognize the relations of the fibrous pericardium to the diaphragm and the pleurae.
Apply your knowledge of the surface anatomy of the pleurae and pericardium to
perform pericardiocentesis. (*see above)
• Fibrous pericardium attaches to central tendon of diaphragm
5) Identify the borders of the heart and the great vessels.
• Orientation of the heart:
o R chambers are to the right and more anterior than L
o L atrium is more posterior
o R atrium inferior to L
•
•
Borders of the heart:
o Right border à R atrium
o Left border à L ventricle
o Superior border à Both atria
o Inferior border à R ventricle
Important structures:
o Apex à point of heart at inferior/L margin; formed by L ventricle
o Base à formed by L atrium; only visible posteriorly
6) Describe the major branches of the great vessels. Discuss the clinical significance of
the transverse pericardial sinus.
• R/L Internal Jugular Veins (drain blood away from head)
o Accompanied by R/L Subclavian veins (drain blood away from
head/upper limb)
o Internal jugular veins join with subclavian veins à R/L brachiocephalic
veins à superior vena cava (SVC) (carries blood from upper part of body
to R atrium)
§ R brachiocephalic vein is short/vertical; L is horizontal/longer
• L must cross midline to get to SVC (greater distance to
cover so longer)
o Inferior vena cava – venous drainage from all of body inferior to diagram
o Summary:
§ R/L internal jugular veins + R/Lsubclavian veins à R/L
brachiocephalic veins
§ R brachiocephalic + L brachiocephalic à SVC à R atrium
•
Ascending Aorta – coming off of L ventricle, changes names as it comes off of
heart and crosses sternal angle
o L ventricle à sternal angle
o Above sternal angle (crosses to superior mediastinum) ascending aorta
à arch of aorta
o Arch loops and begins to run anterior to posterior and then changes
directions and run inferiorly à crosses sternal angle back into inferior
mediastinum à thoracic (descending)
aorta
o SUMMARY:
§ Ascending aorta à inferior
mediastinum
§ Aortic Arch à superior
mediastinum
§ Thoracic (descending) aorta à
inferior mediastinum
•
3 big arteries coming off of arch of aorta:
o Brachiocephalic trunk (runs superiorly away from arch) à which
branches to R subclavian artery (supplies blood to R upper limb and part
of R side of head) & R common carotid artery (supplies blood to part of
R side of head)
§ *R common carotid artery is more anterior
§
o L common carotid (supplies part of L side head/neck) à lies a bit to the
L and posterior
o L subclavian artery (supply L upper limb and part of L head/neck) à lies
to the L/posterior
*Typically no L brachiocephalic trunk
*TRUNK used to describe short artery that almost immediately branches
• Transverse Pericardial Sinus – relatively empty space immediately posterior to
pulmonary trunk and aortic arch
o Clinical significance: can get behind vessels to clamp them off for a great
vessel ligation (to stop blood supply out of heart) during open heart
7) Describe the course of the vagus nerve through the mediastinum.
• Vagus Nerve – cranial nerve IV
o Exits right and left jugular foramina to enter neck
o Pass through the neck and enter mediastinum
o Form plexuses as they move inferiorly:
§ Cardiac plexus à parasympathetic nerves to heart
§ R/L pulmonary plexuses à parasympathetic nerves to lungs
§ Esophageal plexus à parasympathetic to thoracic esophagus
o Rest of vagus:
§ Passes through diaphragm at esophageal hiatus (**T10) to go
from thorax to abdomen
8) Identify the right and left recurrent laryngeal nerves and discuss the clinical
significance of the location of the left recurrent laryngeal nerve within the
mediastinum.
• RIGHT Vagus nerve pathway:
o Enter thorax à enter mediastinum à VERY high up (possibly still in neck
itself) gives off RIGHT RECURRENT LARYNGEAL NERVE
§ Recurrent laryngeal nerve branches off of vagus, hooks under
right subclavian, runs superiorly back to neck to supply
tissue/muscles in the R larynx
• R recurrent laryngeal is deep to R subclavian
• LEFT Vagus nerve pathway:
o Enter thorax à enter mediastinum à give off LEFT RECURRENT
LARYNGEAL NERVE
§ L recurrent laryngeal nerve branches off inferiorly and passes
deep to arch of aorta, passes behind arch, and runs back up into
neck to supply mucosa/muscles in L larynx
§ Clinical significance:
• Where it hooks under the arch, it is immediately superior
to pulmonary trunk and immediately posterior to
ligamentum arteriosum (developmental remnant that
connects pulmonary trunk to aortic arch)
• Very narrow space between pulmonary trunk and aortic
arch à anything that occludes that space will compress L
recurrent laryngeal nerve
o Manifests as hoarseness due to weakness/paralysis
of L larynx muscles
ILM 6 – Mediastinum and Heart II
1) Describe the coronary vessels. Discuss the technique of coronary bypass.
• External Grooves
o Coronary (atrioventricular) groove à separates atria from ventricles
o Anterior/Posterior Interventricular grooves à pair of grooves
anteriorly/posteriorly marking where ventricles meet
• Coronary arteries à 2 coronary arteries arising from ascending aorta
o Right Coronary Artery (RCA)
§ Comes off of R side of ascending aorta
• Travels in R side of coronary groove
§ Branches:
• Almost immediately gives off sinoatrial (SA) nodal branch
(supplies area around SA node) à around inferior margin,
gives off R marginal branch (runs along edge of R ventricle
running toward apex)
• Meanwhile, R coronary artery itself wraps around in coronary
groove (anterior to posterior) and branches to à posterior
interventricular branch (in posterior interventricular groove)
o Left Coronary Artery (LCA)
§ Shorter than RCA
§ Almost immediately splits into 2 branches:
• Anterior interventricular branch (LAD) (runs in anterior
interventricular groove, supplies L ventricle)
o Anterior interventricular branch = L anterior
descending
o Common to have blockages (*very serious because it
supplies L ventricle)
• Circumflex branch runs in coronary groove, wraps around
from anterior to posterior and gives off à L marginal branch
(goes to L margin of heart and supplies L atrium)
•
Coronary Bypass
o Common treatment for MI
o Coronary arteries common sites for blockages à SA nodal branch, LAD,
circumflex branch
o Take vessel grafts OR redirect other vessels so they go around the blockage
in coronary artery
§ In the image, vessels are plugged into the aorta and plugged into
vessels distal to the blockages
•
Venous Drainage
o Coronary Sinus – structure into which veins drain oxygen/nutrient depleted
blood away from heart
§ Drains into R atrium à has separate opening into R atrium
• Alongside SVC/IVC, this is third vessel draining directly into R
atrium
§ “Sinus” = large/formless/thin-walled vein
§ On the posterior aspect of the heart
§ Receives blood from:
• Great Cardiac Vein
o Begins in anterior interventricular groove à drains
alongside anterior interventricular artery à turns in
coronary groove to wrap around L side of coronary
groove, following circumflex branches of L coronary
artery à drains into coronary sinus
• Middle Cardiac Vein
o Runs in posterior interventricular groove à runs
alongside posterior interventricular artery à drains
into coronary sinus
• Small Cardiac Vein
o Runs in coronary groove alongside R coronary artery à
drains into coronary sinus
2) Discuss the internal features of the heart chambers. Relate the thickness of the walls
to the function of each chamber.
• RIGHT ATRIUM
o Openings to receive blood from the IVC, SVC, and coronary sinus
o Rough, muscular areas on parts of R atrium wall à pectinate muscles
Pectinate muscles confined to right auricle (protrudes anteriorly
on R atrium)
§ Pectinate muscle ends abruptly at the crista terminalis à ridge
separating pectinate muscle and auricle from the smooth wall
portion of atrium
o Rest of R atrium is smooth wall (not muscular, not contractile)
§ Interatrial septum à separating R/L atria
§ Fossa ovalis (*fetal remnant of foramen ovale) à very thin wall
of inter-atrial septum (translucent)
§
•
RIGHT VENTRICLE
o Trabeculae Carneae (“meat ridge”) à muscular ridges, much thicker
than atrium
§ Contractile portion of R ventricle
§ Thick to pump blood to lungs
o Papillary muscles (*3) à each associated with a leaflet of tricuspid valve
§ Connected to the leaflets via chordae tendineae
§ Allows tricuspid valve to prevent blood from refluxing from R
ventricle back to R atrium during ventricular contraction
o Interventricular septum à thick septum separating R/L ventricles
o Septomarginal Trabecula (moderator band) à string of tissue extending
from interventricular septum to inner papillary muscle
§ Carries electric signal to interior papillary muscle so that when it
contracts, it does it in unison with other 2 papillary muscles
•
LEFT ATRIUM
o Receives blood from the 4 pulmonary veins
o Smooth walled, rounded area above second to right arrow in image
below is the fossa ovalis
o Left auricle à smaller than R, only muscular portion of L atrium
§
•
Pectinate muscles associated with it
LEFT VENTRICLE
o VERY thick walls (2x thicker than R vent)
§ Needs to generate enough pressure to push blood throughout
entire body
o Trabeculae carneae à muscular/contractile portion
o 2 papillary muscles à 1 for each leaflet of mitral valve
§ Connected to mitral valve by chordae tendineae
3) Compare and contrast the structure and function of the heart valves.
• TRICUSPID (R atrioventricular) VALVE à allows blood to flow from R atrium to R
ventricle
o 3 leaflets/cusps
o Opens passively during atrial contraction
o Closes during ventricular contraction
§ As ventricle contracts, pushes leaflets against the wall of the
atrium, which pulls on chordae tendinea in R ventricle à become
tighter and tries to resist being pulled farther away
§ Papillary muscles stimulated to contract à pulls on chordae
tendineae more to become taught à completely closes valve to
prevent reflux
•
PULMONARY (Semilunar) VALVE à allows blood to flow from R ventricle to
pulmonary trunk
o Pulmonary sinuses à 3 leaflets of pulmonary valve
§ Convex UP when blood is pumped from ventricle to pulmonary
trunk
§ But when pressure of contraction is released, blood will naturally
fall back toward ventricle à fills pulmonary sinuses & pushes the
leaflets back together to seal off pulmonary valve
•
MITRAL (Left Atrioventricular) VALVE
o 2 cusps
o L atrium à L ventricle
o Opens passively during atrial contraction
o Closes during ventricle contraction
§ Papillary muscles/chordae tendineae will pull valve closed
•
AORTIC VALVE
o L ventricle à aorta
o Almost identical to pulmonary valve
§ *One important difference: a few blood vessels arise from aortic
valve sinuses
o 3 sinuses that open during L ventricle contraction
§ As blood falls back, it will fill the sinuses and close aortic valve off
to blood flowing back into L ventricle
o R/L coronary arteries open off of aorta into the sinuses
§ As blood fills the leaflets, blood will also flow into R/L coronary
arteries
• This is good because it is blood that is just falling, rather
than being pumped with ventricular contraction
o Coronary vessels will be under less pressure
4) Contrast the structure of the fetal and adult heart and great vessels and compare the
flow of blood through each. Identify the remnants of fetal structures in the adult
heart.
• Postnatal (adult) circulation
o IVC/SVC/coronary sinus à R atrium à tricuspid valve à R ventricle à
pulmonary valve à pulmonary trunk à R/L pulmonary arteries
o From lungs via 4 pulmonary veins à L atrium à mitral valve à L ventricle à
aortic valve à ascending aorta/arch/thoracic aorta
•
Fetal Circulation
https://www.youtube.com/watch?v=zTXmaVgobNw
*Lungs are full of fluid à no gas exchange
*Blood is oxygenated/gets nutrients from placenta
VENOUS
o Oxygen rich blood comes from placenta via umbilical vein à bypasses liver
through structure called ductus venosus
§ Blood gets nutrients from placenta so liver doesn’t have much to do;
still some mixing, so oxygen saturation begins to decline
o Ductus venosus à IVC à R atrium à shunted through foramen ovale (hole
in interatrial septum) directly to L atrium à L ventricle à ascending
aorta/arch/thoracic aorta à umbilical arteries (going back to placenta, run
alongside umbilical vein)
*image below shows oxygen saturation from HIGH to LOW
ARTERIAL
o A lot of oxygen/nutrient poor blood coming from head/neck à SVC à R
atrium à R ventricle à pulmonary trunk à ductus arteriosus (connects
pulmonary trunk to arch of aorta) à blood will mix with oxygen rich blood in
arch/thoracic aorta à umbilical arteries
o **thoracic aorta has a mix of some oxygen rich/poor blood à intermediate
composition
**Umbilical vein à most oxygen rich blood (going TO heart, so still a vein)
**Umbilical arteries à oxygen poor blood (going AWAY from heart, so arteries)
**Fetal Circulation Notes
• Bypasses:
o Liver
§ Ductus Venosus
o Heart
§ Foramen Ovale (R atrium à L atrium)
• Allows oxygen RICH blood from IVC to be shunted directly
from R atrium à L atrium (bypassing R ventricle and
pulmonary circuit)
§ Ductus Arteriosus (pulmonary trunk à aorta)
• Allows oxygen POOR blood from SVC into R atrium à ventricle
à pulmonary trunk to bypass pulmonary circuit and go
DIRECTLY à aorta
o Joins the arch of the aorta just distal to where last of
the great vessels come off of arch
§ These great vessels are taking very oxygenated
blood to brain/upper body (important that it’s
“good” blood) à it’s okay if blood coming from
R ventricle into ductus arteriosus/aorta isn’t as
oxygenated
•
Notes:
*SVC has oxygen POOR blood, while IVC has oxygen RICH blood à how do they
remain separate?
-Hemodynamics of blood moving in different directions prevents mixing
-Foramen ovale is positioned well for blood being shot up from IVC to go
directly into it, while SVC shooting blood down allows it to go into R
ventricle
After birth:
o Fetal foramen ovale à fossa ovalis (adult remnant)
§ Foramen ovale closes at birth; fluid pressure from blood in the R/L
atrium holds flaps of foramen ovale together à forms fossa ovalis
(within 3 months)
o Fetal ductus arteriosis à ligamentum arteriosum (adult remnant)
§ Blood stops flowing through ductus arteriosis
• It’s easier for blood to go from pulmonary trunk to pulmonary
arteries à becomes ligamentum arteriosum (within 3 weeks)
o Fetal ductus venosus à ligamentum venosum
5) **Recognize conducting system of the heart
• SA (sinoatrial) node (junction of SVC and R atrium)
o Stimulated by sympathetic, inhibited by parasympathetic
• AV (atrioventricular) node
o Spot in interatrial septum where all 4 chambers come together
o Signal from SA node runs along walls of R atrium à AV node
o **AV node stimulated by atrial contraction
o AV node signal à AV bundle à splits into R/L bundles on R/L sides of
interventricular septum à some will split to moderator band on R
ventricle BUT overall propagated to ventricles and causes them to
contract
6) Identify the esophagus and thoracic duct and describe their courses through the
mediastinum.
• Esophagus à flattened tube, runs entire length of thorax connecting pharynx
(neck) with stomach (abdomen)
o Lies medially; to the right of thoracic aorta, directly anterior to vertebral
bodies
o In superior mediastinum
§ Lies posterior to trachea, anterior to vertebral bodies
• Trachea c-shaped hyaline is open in back because
esophagus needs flexibility to expand with swallowing
o In inferior mediastinum
§ Lies posterior to base of heart (primarily L atrium)
o Passes through diaphragm from thorax à abdomen via esophageal
hiatus (T10)
•
Thoracic Duct à major/biggest lymphatic vessel; close to the midline of posterior
mediastinum
o Lies on vertebral bodies à L of azygous vein, R of aorta
o Runs entire length of mediastinum/thorax
o Drains fluid from almost entire body superiorly into à L venous angle
(junction of L subclavian vein and L internal jugular vein where they come
together to form L brachiocephalic vein)
•
Right Lymphatic Duct à drains everything in RUQ (yellow in image)
o R limb, R side of thorax, R side of head
o Drains into R venous angle à where R subclavian vein and R internal jugular
vein come together to form R brachiocephalic vein
7) Describe the vessels of the descending aorta and azygos system.
• Descending Aorta
o Continuation of arch of aorta at sternal angle
o Left of midline (L of esophagus and vertebral bodies)
o Passes from thorax à abdomen at aortic hiatus (T12) of diaphragm
o Gives off many (relatively small) branches:
§ Bronchial arteries à supplies tissues of lungs
§ Esophageal arteries à supplies esophagus
§ Posterior intercostal arteries (*VAN) à running through intercostal
spaces
•
Azygous System
o Formed by veins of posterior mediastinum (relatively small veins)
§ Primary venous drainage of thorax/parts of superior abdomen
§ NO valves
§ “Azygous”=”without yolk” à unpaired vein
o Azygous Vein
§ Biggest in the system; R of midline; usually no developed L side
equivalent
§ Receives blood from:
• Bronchial veins à drain lungs into azygous
• Esophageal veins à draining esophagus
• Posterior intercostal veins à draining posterior intercostal
spaces
• Subcostal vein à drains lower vertebrae
• Lumbar vein à drains lower vertebrae
§ Azygous vein drains à SVC
• Azygous vein arches over root of R lung à drains into SVC
immediately before SVC à R arium
§ Accessory veins on L side of thorax
• Accessory hemiazygous
o L of midline, more superior, drains into azygous vein
• Hemiazygous Vein
o L of midline, more inferiorly drains into/joins azygous
8) Identify the sympathetic trunk and the thoracic splanchnic nerves and describe their
courses through the mediastinum.
• Sympathetic Trunks
o Series of paravertebral ganglia connected to each other in a chain via axons
o Connected to ventral rami (i.e. intercostal nerves in the thorax) via white and
gray rami communicantes
§ White=in // gray=out
•
Thoracic Splanchnic Nerves
o Carry preganglionic sympathetic fiber that target abdominal organs
§ Split from sympathetic trunk in thorax, pass through diaphragm,
synapse in abdomen
9) Recognize the 3D relationships of the major organs, vessels, and nerves within the
mediastinum.
ILM 7 – Anterior Abdominal Wall
1. Identify the iliac crests, anterior superior iliac spines, pubic tubercles, and pubic
symphysis.
-2 os coxae on either side à 3 bones that fuse into 1 through development
-Iliac crest at L4
-Pubic symphysis is where L/R pubis and L/R os coxae meet (cartilaginous joint)
-Palpable landmarks: iliac crest, ASIS, pubic tubercles
-Umbilicus à ½ way between xiphoid process & pubic symphysis
**L4 vertebral level
2. Define the median, transumbilical, and transpyloric planes and the abdominal
quadrants.
•
•
Transumbilical plane à L4 (iliac crests)
Transpyloric plane à L1 (1/2 way between umbilicus and xyphoid)
o No associated with any external landmarks, but very busy area internally
3. Describe the fascial and muscular layers of the abdominal wall. Relate the fascial
layers to the spread of blood or infection into adjacent regions.
• Abdominal Fascia INFERIOR TO UMBILICUS
o 2 layers:
§ Camper fascia à superficial fatty layer
§ Scarpa fascia à deep membranous layer
• Connects with pubis inferiorly à limits spread of
fluids/infection in anterior abdomen into thigh
•
Abdominal Fascia SUPERIOR TO UMBILICUS
o Undifferentiated superficial fascia
•
Other:
o Deep (investing) Fascia à thin layer of connective tissue surrounding
each muscle of anterior abdominal wall (thin film covering muscle)
o Transversalis Fascia à deep to all muscles of anterior wall
§ Thin layer of connective tissue separating muscles of anterior
abdominal wall from peritoneal cavity deep to it
Labia Majora/Scrotum
o Developmentally homologous to anterior abdominal wall à extensions
of this area into anterior pelvic region
o Similar structurally (especially the layers of connective tissue)
o Scrotum:
§ Dartos fascia à continuous with scarpa layer of superficial fascia
of anterior abdominal wall
• Clinical implication: no separation between the two, so
easy for fluids/infection to spread to/from abdomen
to/from stratum
§ Dartos muscle à smooth muscle fibers embedded into dartos
fascia
• Function: wrinkles skin of scrotum to reduce surface area
& reduce heat loss to cold external environment
o Labia Majora:
§ Scarpa fascia of labia majora continuous with scarpa layer of
superficial fascia of anterior abdomen wall
•
4. Compare the composition of the rectus sheath superior and inferior to the arcuate
line.
• Abdominal Muscles
o Superficial à deep
§ External oblique
• Fibers run IN/DOWN (hands in pockets)
§ Internal oblique
• Fibers run IN/UP (hands into gloves, toward xiphoid)
§ Transverse abdominis
• Fibers run transverse (lateral to medial)
o Rectus Abdominis
§ At midline, series of shorter segments separated by inner tendons
§ Fibers run vertically, entire length of abdomen
•
Rectus sheath
o Covers rectus abdominis
o Tendon material à aponeurosis
§ Sheath-like tendon (stretchy/elastic in sheet shape rather than
a normal tendon cord)
o Lateral muscles (external/internal oblique, rectus abdominis) have a
bony origin posteriorly, and fibers insert on tendon, and two tendons
from contralateral muscles meet at the midline linea alba
o Linea alba à all aponeurosis of rectus sheath meet here
o Arcuate line à 1/3 distance between umbilicus and pubis
§ Marks area where relationship between lateral aponeurosis
and rectus abdominis changes
o SUPERIOR to arcuate line:
§ Rectus abdominis enclosed by 1.5 aponeurosis anteriorly and
1.5 posteriorly
§ Breakdown:
• Aponeurosis of external oblique runs anterior to
rectus abdominis
• Aponeurosis of internal oblique splits à ½ runs
anteriorly, ½ runs posteriorly to rectus abdominis
• Aponeurosis of transverse abdominis runs posterior to
rectus abdominis
o INFERIOR to arcuate line:
§ All three aponeuroses run anterior to rectus abdominus
• **only thing deep to rectus sheath is transversalis
fascia
o Clinical significance:
§ Surgery superior to arcuate line à get through rectus
abdominis and still have 1.5 layers of fibrous aponeurosis to
get through until you get to the transversalis fascia and
peritoneum
§ Surgery inferior to arcuate line à once through rectus
abdominis, only transversalis fascia/peritoneum deep to
rectus abdominis
5. Define the dermatome levels present on the abdominal wall. Describe the nerves that
provide the motor and sensory innervation to the abdominal wall (including the
inguinal region, scrotum, and labia majora).
• Dermatomes
o T7 – xyphoid process
•
o T10 – umbilicus
o T12 – pubis
o L1 – inguinal fold
Nerves
o Abdominal wall nerves are ventral rami of:
§ T7-T11 à intercostal nerves
§ T12 à subcostal nerve
§ L1 à 2 branches:
• Iliohypogastric nerve
• Ilioinguinal nerve
o Functions: (*think intercostal!)
§ Somatic Motor
§ Somatic Sensory (pain/temp/touch)
§ Sympathetic (pili, BV, sweat glands)
6. Discuss the blood supply, venous and lymphatic drainage of the abdominal wall and
sites of potential venous anastomoses.
• Arteries of Abdominal Wall
o Posterior Intercostal Arteries and Subcostal Artery (inferior to PIA)
o Within rectus sheep, deep to rectus abdominis is a pair of arteries:
§ Superior epigastric artery à branch of internal thoracic
§ Inferior epigastric artery à branch of external iliac artery
• **These anastamose deep to rectus abdominis
o Superficial Epigastric Artery à branch of femoral artery
•
•
•
Veins of Abdominal Wall
o Superior Epigastric Vein à drains to SVC
o Inferior Epigastric Vein à drains to IVC
Venous Anastomoses
o Caval-caval anastamose
§ Superior epigastric vein + inferior epigastric vein
§ Normally, venous drainage happens inferiorly and superiorly
§ Clinical significance: if there is a blockage/compression of IVC (ex:
ascites) blood that would normally flow from inferior epigastric à IVC
can instead flow to superior epigastric vein à SVC
o Portal-Caval Anastomose
§ Connection between blood flowing directly to IVC + blood flowing
into portal system
§ Portal System: blood flowing from digestive organs drains first into
liver for processing à IVC à heart
§ Anastomose explanation:
• Paraumbilical veins (small veins around umbilicus that
normally drain to portal system) anastomose with superficial
epigastric vein à femoral vein à IVC à heart
• Bypasses portal system in cases of liver blockage/disease that
makes it hard to push blood through liver
o Concern is that these veins are very small and don’t
handle high volume of blood very well so they become
varicose/distended and visible superficially à Caput
Medusae
Lymphatic Drainage
o Superior Umbilicus à drains to axillary lymph
nodes
o Inferior Umbilicus à drains to superficial inguinal
lymph nodes
7. Identify the inguinal ligament, inguinal canal (including deep and superficial rings),
spermatic cord, and round ligament of the uterus. Relate the structure of the adult
inguinal canal to the embryonic descent of the gonads.
• Inguinal Ligament – free inferior edge of external oblique aponeurosis
o Stretches from ASIS à pubic tubercle
• Inguinal Canal – passageway from abdominal cavity to superficial areas of
scrotum/labia majora
o Superior to inguinal ligament
o Deep Inguinal Ring – “entrance” à faces into peritoneal cavity in abdomen
(posterior/superior)
§ Lateral to inferior epigastric vessels
§ About ½ way to ASIS and pubic tubercle
o Superficial Inguinal Ring – “exit” à directed toward scrotum/labia majora
(anterior/inferior)
§ Superolateral to pubic tubercle (not at end of inguinal ligament, but
close)
o **Area of weakness in all of the layers of muscle/fascia à leads to herniation
(but usually, abdominal pressure is enough to keep the rings closed)
Why do we have Inguinal Canal??? à gonad development
• Male Inguinal Canal Ontogeny à Testes
o Testes develop within the abdomen (posterior abdominal wall) à during
development they travel outside of abdominal cavity (scrotum)
o Gubernaculum – connective tissue that connects testes to scrotum
§ Runs entire distance of posterior abdominal wall through what will
become inguinal canal to scrotum
§ As fetus develops, all structures get bigger EXCEPT for gubernaculumà
causes a pull of testes from posterior abdominal wall à deep ring of
inguinal canal à superficial ring of inguinal canal à into scrotum
• As this happens, testes also bring vessels/nerve supply and ductus
deferens à forms spermatic cord
o **PRIMARY contents of inguinal canal**
•
Female Inguinal Canal Ontogeny à Ovaries
o Ovaries develop in posterior abdominal wall and descend
o Gubernaculum connects ovaries to labia à grows very slightly (unlike males), so
ovaries move inferiorly but don’t go all the way through inguinal canal
§ Remnants form 2 ligaments:
• Ovarian ligament (ovary à uterus)
• Round ligament (uterus à through inguinal canal à labia
majora)
o ROUND LIGAMENT is primary content of inguinal canal in females
Innervation of the Inguinal Canal
• Ilioinguinal Nerve (L1)
o Sensory à inguinal region, scrotum/labia majora
• Genital branch of genitofemoral nerve (L1/L2)
o Sensory à inguinal region, scrotum/labia majora
o Motor à cremaster muscle
8. Relate the layers of the scrotum and spermatic cord to the corresponding layers of the
abdominal wall.
As testes travel through inguinal canal, they bring with them layers of abdominal wall:
• Drags transversalis fascia à forms internal spermatic fascia
• *testes go through transversus abdominis without pulling anything with them
• Drags internal oblique muscle/aponeurosis à forms cremaster muscle and fascia
o Cremaster muscle – skeletal muscle that contracts to pull testes closer to
body/raises them to keep them warm
• Drags portion of external oblique aponeurosis into scrotum à forms external
spermatic fascia
9. Differentiate between direct and indirect inguinal hernias.
*More common in males
• Indirect (congenital) Inguinal Hernia
o Some part of abdominal contents enters deep inguinal ring à passes lateral
to inferior epigastric vessels (*because the deep ring itself does this) à goes
through inguinal canal
o Reason for name:
§ Congenital à contents passing a congenital, “already there”
passageway
§ Indirect à not taking the shortest distance to anterior surface
•
Takes inguinal canal which goes deep/lateral to
superficial/medial
o If they make it far enough, they exit superficial ring and enter scrotum/labia
majora
o Most common type of inguinal hernias
•
Direct (Acquired) Inguinal Hernias
o Direct because they go straight from deep à superficial (*shortest distance
out of abdominal cavity)
o Pass through an area of weakness called inguinal triangle:
§ Bordered medially by rectus abdominis
§ Bordered laterally by inferior epigastric vessels
§ Bordered inferiorly by inguinal ligament
o Abdominal contents push into peritoneum/transversalis fascia à make new,
acquired opening medially to inferior epigastric vessels à abdominal
contents will then enter posterior wall of inguinal canal
§ *don’t traverse entire length of inguinal canal so they don’t take
fascia/muscle with them à just protrude out
§ Rarely enters scrotum à IF THEY DO **** they lie lateral to and
outside of spermatic cord
• Versus indirect which takes fascial coverings AND enters
spermatic cord)