SKELETAL SYSTEM
PART 2
THE AXIAL SKELETON
Honors Anatomy & Physiology
Essential Question

What is the main contribution the axial
skeleton makes to homeostasis?
Divisions of the Skeleton






AXIAL SKELETON
Skull

 Cranium

 Face

Hyoid
Auditory Ossicles
Vertebral Column
Thorax


APPENDICULAR
SKELETON:
Pectoral Girdle
Upper Limbs
Pelvic Girdle
Lower Limbs
Types of Bone

bones fall into 1 of 5 main types based on
shape:
 Long
 Short
 Flat
 Irregular
 Sesamoid
Long Bones



longer than they are wide
may be slightly curved (to absorb stress of
weight at more points along the bone i.e.
straight bones would fracture more easily)
consist of:
 shaft
& variable #s of ends
 compact bone in diaphysis and spongy bone in
epiphysis
Long Bones
Short Bones



somewhat cube-shaped
nearly equal in length as width
consist of:
 spongy
bone except @ surface
Short Bones
Flat Bones

Composed of:
2
nearly parallel plates of compact bone
enclosing spongy bone inside

Function:
 give
considerable protection
 place for muscle attachment
Flat Bones
Irregular Bones


complex shapes (do not fit in other categories)
vary in amt spongy bone
Sesamoid Bones



develop w/in certain tendons where there is
considerable friction, tension, & physical
stress
function: protect tendon from excessive wear
& tear
vary in # person to person but everyone has 2
patella which develop in quadriceps femoris
tendon
Sesamoid Bone
Sutural Bones


classified by location (w/in a suture: a seam
between 2 cranial bones)
not everyone has them
Bone Surface Markings

1.
2 major types:
depressions & openings

2.
form joints or allow passage of vessels &
nerves
processes

projections or outgrowths that either help form
joints or serve as attachment points for
ligaments & tendons
Bone Surface Markings
Bone Surface Markings-2
Axial skeleton
SKULL
Skull

1.
22 bones in 2 categories:
Cranium
8 bones that form cranial cavity

1.
2.
3.
4.
5.
6.
1 frontal bone
2 parietal bones
2 temporal bones
1 occipital bone
1 sphenoid bone
1 ethmoid bone
Skull
2. Facial Bones
14 bones that form the face

2 nasal bones
 2 maxillae
 1 mandible
 2 zygomatic
 2 lacrimal
 2 palantine
 2 inferior nasal conchae
 1 vomer
Skull: Cavities
1.
2.
3.
4.
5.
Cranial Cavity
Nasal Cavity
Orbits
Paranasal Sinuses
Middle & Inner Ear Cavities
Cavities of the Skull
Movable Joints of the Skull
1.
2.
Mandible
Auditory Ossicles
Functions of Cranial Bones
1.
2.
3.
protecting brain
stabilizing position of brain, vessels, &
nerves through attachments to the meninges
outer surfaces provide large areas of
attachment for muscles that move parts of
the head & some for facial expression
Cranial Bones: Frontal Bone

forms:
 forehead
 upper part of eye socket
 most of anterior part of cranial floor
 in newborns: rt & lt which fuse shortly after
birth
Frontal Bone
Parietal Bones

form greater portion of sides & roof of
cranial cavity
Temporal Bones



form inferior, lateral aspects of the cranium
& part of the cranial floor
its zygomatic process forms the lateral half of
the zygomatic arch
mandibular fossa: where condylar process of
mandible forms TMJ (temporal mandibular
joint)
Temporal Bones
Temporal Bones


external auditory meatus: ear canal
mastoid: posterior & inferior to external
auditory meatus, contains “air cells”
(mastoiditis: inflammation in air cells)
Temporal Bone: Petrous Portion



base of skull between sphenoid & occipital
bones
houses middle & inner ear
Carotid foramen & Jugular foramen
Temporal Bones


internal auditory meatus: passage of Cranial
nerves VII (facial n.) and VIII
(vestibulocochlear n.)
styloid process: point of attachment for
muscles & ligaments of the tongue & neck
Temporal Bone: Internal Surface
Occipital Bone



forms back of head & most of base of skull
foramen magnum: large hole spinal cord
passes thru,
occipital condyles: articulate with 1st cervical
vertebra (atlas)
Occipital Bone
Sphenoid Bone



middle base of skull
*articulates with all other cranial bones
shape resembles a bat
Sphenoid Bone


sella turcica: (Turkish saddle) the “seat” of
the saddle is the hypophyseal fossa: where
the pituitary gland sits
optic foramen: between body & lesser wings,
cranial nerve II (optic n.) and opthlamic
artery pass thru
Sphenoid Bone
Ethmoid Bone




“like a sieve”
midline of anterior part of cranial floor,
anterior to sphenoid, posterior to nasal bones
cribiforme plate: forms roof of nasal cavity,
the holes of the sieve where olfactory nerves
pass from roof of nasal cavity to brain
crista galla: triangular process which serves
as pt of attachment for meninges of brain
Ethmoid Bone
Ethmoid Bone


perpendicular plate: forms superior portion
of nasal cavity
superior & middle nasal conchae: (or
turbinate) increase vascular & mucous
membrane surface area in nasal cavities: aids
in sense of smell, warms, filters & moistens
air being inhaled. Filters because the
turbinates cause air to swirl as a result
inhaled particles strike & become trapped in
mucus
Ethmoid Bone
“Sometimes when you study anatomy, you
start seeing others differently.”
Facial Bones

shape of face changes dramatically during 1st
2 yrs of life:
 brain & cranial bones expand
 1st set of teeth erupt
 paranasal sinuses enlarge
 growth of face stops ~16 years old
Facial Bones

1.
2.
3.
4.
5.
6.
7.
8.
14 facial bones:
2 nasal bones
2 maxillae
2 zygomatic bones
1 mandible
2 lacrimal bones
2 palatine bones
2 inferior nasal conchae
1 vomer
Nasal Bones

form part of the bridge of the nose (rest is
cartilage)
Maxillae





= upper jaws
*articulate with every bone in face except the
mandible
form part of floor of orbits, parts of nasal
cavity, & most of the hard palate (bony roof
of mouth)
each one has large maxillary sinus
alveolar process is small arch that contains
the alveolar sockets for upper set of teeth
Maxillae
Cleft Palate & Cleft Lip


10-12 wks gestation the palatine processes of
maxillae typically join
not doing so  cleft palate +/- cleft lip
 speech
& swallowing can be affected
 many ear infections
 reparative surgery recommended 1st few wks of
life / surgery needs to be completed by 12 – 18
mos b/4 speech: speech therapy & orthodontic
care frequently necessary
Zygomatic Bones


“cheekbones”: the
temporal process of
the zygomatic bone
articulates with the
zygomatic process
of the temporal
bone
also part of floor of
orbit
Lacrimal Bones



thin, about the size of pinky fingernail
(smallest bones of face
part of medial wall of each orbit
each contain lacrimal fossa that houses
lacrimal sac: gathers tears  nasal cavity
Inferior Nasal Conchae


inferior to the middle nasal conchae of the
ethmoid bone forming part of lateral wall of
nasal cavity
same function as superior & middle conchae:
swirling inhaled air to deposit particulates
but not involved in sense of smell
Vomer

Δ shaped bone on the floor of nasal cavity
forming inferior portion of nasal septum
Mandible



largest & strongest facial bone (lower jaw)
alveolar processes hold lower teeth sockets
mental foramen: dentist numb mental nerve
Sutures


an immovable joint in an adult found only
between skull bones & holds most skull
bones together
name generally reflects bones they unite
Sutures
Newborn Skull
Newborn Skull
Hyoid Bone






“U-shaped “
*does not articulate with any other bone in
skeleton
suspended by ligaments from styloid process
of temporal bone
in anterior neck between mandible & larynx
function: supports tongue
*frequently fractured during strangulation
Hyoid Bone
Vertebral Column



aka spine, backbone
2/5 of person’s height
26 in adult (starts as 33, some fuse to form
sacrum & coccyx)
7
cervical
 12 thoracic
 5 lumbar
 1 sacrum
 1 coccyx
Vertebral Column



Fetus has anteriorly
concave curve
3 mos old when holds
head cervical curve
develops
lumbar curve
develops as infant sits
up, stands, walks
Intervertebral Discs

between bodies of consecutive vertebra
 under
compression they flatten & broaden
 harden, less elastic w/aging & narrow  loss of
height


annulus fibrosus: outer fibrous ring
nucleus pulposus: inner soft, highly elastic
Intervertebral Discs
Parts of a Vertebra

Body
 thicker,

anterior portion, weight bearing portion
Vertebral Foramina
 contains
vessels

spinal cord, adipose, areolar CT, blood
Spinous Process
1
of 7 processes, posterior, palpable on back of
body
Transverse Processes: on each side, extending
laterally
Vertebrae: 1st & 2nd Cervical

Atlas
 ring-shaped
 articulates
with
condyles of
occipital bone
 allows you to nod
head “yes”

Axis
 2nd
cervical v.
 allows you to shake
head “no”
Typical Cervical Vertebrae



C-3 to C7
smaller than other v.
except coccyx but
vertebral foramen
largest
all cervical v. have
extra foramen: 2
transverse foramen for
vertebral a., v., & n.
Typical Thoracic Vertebrae



T-1 to T-12
larger & stronger
than cervical v.
distinguishing
feature: articulate
with ribs (facets on
transverse
processes of T-1 to
T-10
Typical Lumbar Vertebrae



L-1 to L-5
largest & strongest
of the vertebrae
processes are short
& thick
Sacrum



triangular bone
formed by union of
S-1 to S-5
fusion begins ~16,
complete by age 30
female: shorter,
wider, more curved
S-2 to S-3
Coccyx



small triangle
formed by fusion of
4 coccygeal v. (Co-1
to Co-4), start
between 20 & 30
females points
inferiorly; males it
points anteriorly
Thorax


refers to entire chest
skeletal part of thorax is thoracic cage
 Sternum
 Ribs
Sternum



aka “breastbone”
flat bone in center of anterior thorax
3 bones that fuse by age 25
Sternum
1.





Manubrium
superior portion
suprasternal notch
clavicular notches
articulates with costal
cartilage of 1st & 2nd rib
sternal angle: where it
articulates with body
Sternum
2. Body
 middle & largest
portion
 articulates with
costal cartilage of
2nd thru 10 ribs
Sternum
3. Xiphoid Process
 cartilagenous in
infancy
 not completely
ossified until ~age
40
 avoid it during CPR
Ribs: 12 Pair




increase in length 1st thru 7th then decrease in
length to 12th
1st thru 7th ribs (true ribs) have direct anterior
attachment to sternum by strip of hyaline
cartilage which contribute to elasticity of
thoracic cage
8th thru 10th ribs attach to each other & then
to cartilages of 7th rib
11th & 12th ribs: floating ribs
Ribs
Ribs


1.
2.
3.
4.
5.
all 12 attach posteriorly to vertebrae
Parts of a Rib
Head
Neck
Tubercle
Body
Costal Angle
Abnormal Curvatures of Spine



Scoliosis
lateral bending
usually in thoracic
region
Abnormal Curvature of Spine



Kyphosis
exaggeration of the
thoracic curve
seen in TB of spine,
congenital
malformation,
elderly
Kyphoscoliosis
THAT’S ALL FOLKS