Download Axial skeleton is shown in green

The Axial Skeleton
I highly recommend Professor Wissman’s sites

For bones:
http://homepage.smc.edu/wissmann_paul/bones/EBbon
estutorial.html

Check out all his links:
http://homepage.smc.edu/wissmann_paul/anatomy1/
Also check out:

Site for xrays & other diagnostic procedures:
http://www.radiologyinfo.org/en/sitemap/category
.cfm?category=diag
This is an example of
Prof Wissman’s bone
site; this doesn’t show
the roll-over answers
http://homepage.smc.edu/wissmann_paul/bones/EBbonestutorial.html
THE SKELETAL SYSTEM
The Axial Skeleton

The skeleton consists of
 Bones
(206)
 Cartilages
 Joints – also called articulations, are the
junctions between skeletal elements
 Ligaments – connect bones

Divided into axial and appendicular

Axial skeleton - forms long axis of body
 Skull
 Vertebral
column
 Thoracic cage

Appendicular skeleton – appendages and
what they attach to
 Upper
limbs (arms)
 Pectoral girdle (shoulder)
 Lower limbs (legs)
 Pelvic girdle
Axial skeleton
Skull
Vertebral column
Thoracic cage
Axial skeleton is shown in green
The Skull

Cranial bones (or cranium)
 Enclose
the cranial cavity, which supports and protects
the brain
 Attachment sites for some head and neck muscles

Facial bones (anterior aspect of skull)
 Form
framework of face
 Form cavities for sense organs of sight, taste and smell
 Provides openings for passage of air and food
 Hold the teeth
 Anchor the muscles of the face
Cranium

Vault – “calvaria” = skullcap
 Forms
superior, lateral and
posterior aspects of skull,
and forehead

Base or floor: inferior part
 Prominent
bony ridges divide
cranial base into 3 “fossae”
(steps) – anterior, middle and
posterior
Anterior cranial
fossa
Middle cranial
fossa
Posterior cranial
fossa
(looking down on the floor of the skull)
Cranial bones
Frontal bone
 Parietal bones (paired)
 Occipital bone
 Temporal bones (paired)
 Sphenoid bone
 Ethmoid bone

Cranial bones
frontal
parietal
parietal
parietal
_______sphenoid
temporal
_____ethmoid
occipital
occipital
Temporal bones
this is the right temporal bone
looking at it from the right side
Small cranial bones…
Sphenoid
Ethmoid
Sutures



Immovable, interlocking joints of flat bones of
skull
Irregular, saw-toothed appearance
Largest 4 skull sutures: where bones articulate
with parietal bones
 Coronal
 Sagittal
 Squamous
 Lambdoid
(FIND THEM)
Find: coronal, squamous and lamboid sutures
Find: sagittal and lambdoid sutures
Cranial “cavity” – houses brain
 Smaller cavities

 Housing
middle and inner ear
 Nasal cavity
 Orbits
 Sinuses

Openings (foramina, canals, fissures) for:
 Spinal
cord
 Blood vessels
 Twelve cranial nerves: I-XII
Remember, the skull is composed of:
1.
Cranial bones (or cranium)
[these were just reviewed]
and
2.
Facial bones (anterior aspect of skull)





Form framework of face
Form cavities for sense organs of sight, taste
and smell
Provides openings for passage of air and food
Hold the teeth
Anchor the muscles of the face
Facial bones








Mandible
Vomer
Maxillae (paired)
Zygomatics (paired)
Nasal (paired)
Lacrimal (paired)
Palatines (paired)
Inferior nasal conchae (paired)
Facial bones: Mandible
Vomer
Maxillae (paired)
Zygomatics (paired)
Nasal (paired)
Lacrimal (paired)
Palatines (paired)
Inferior nasal conchae
(paired)
Maxilla (there are 2 which
fuse, forming the upper jaw)
Mandible (lower jaw)
(part of slide 18)
nasal bone
Nasal cavity
ethmoid



Of bone and cartilage
Roof is ethmoid’s
cribriform plate
Floor formed by palatine
processes of the 2
maxillae and horizontal
plates of palatine bones
 These
nasal-floor
structures form roof of the
mouth, called the hard
palate
inf nasal concha
maxilla___________
vomer
Nasal cavity
To left, bones forming the left
lateral wall of the nasal cavity
(nasal septum removed)
To right, nasal cavity with nasal septum
in place, showing how the ethmoid
bone, septal cartilage, and vomer make
up the septum
Orbit
Cone-shaped bony cavities holding the eyes,
muscles that move the eyes, some fat and tearproducing glands; you don’t need to know all these
bones that form it, just realize how complex it is and
recognize the optic canal (optic nerve passes out
through it)
(right orbit shown)
Paranasal sinuses
Air-filled sacs in the bones
 “Paranasal” because they cluster around
and connect to the nasal cavity

Hyoid bone



Only bone which does not
articulate with any other
bone
Moveable base for the
tongue
Points of attachment for
neck muscles that raise
and lower the larynx
during swallowing
Remember that the
Axial skeleton includes:
Skull
Vertebral column
Thoracic cage
Axial skeleton is shown in green
The Vertebral Column

Fetus and infant: 33 separate
bones, or vertebrae

Adult: 24 vertebrae
 Inferior
9 have fused forming
The sacrum (5) and
 The coccyx (4)

Vertebrae
Cervical – 7
 Thoracic - 12
 Lumbar - 5
 Sacrum (5 fused)
 Coccyx (4 fused)

Spinal curvatures



Cervical and lumbar are
concave posteriorly* (lordosis)
Thoracic and sacral are
convex posteriorly* (kyphosis)
Abnormal (see lab book p120):

Too much of either
 Scoliosis (more than 10 degrees
of lateral curvature)
*when viewed from the side
Abnormal curvatures
Non-bony parts

Intervertebral
discs
 anulus
fibrosis
and nucleus
pulposus)



Anterior
longitudinal
ligament
Posterior
longitudinal
ligament
Ligamentum
flavum
Anterior longitudinal ligament: wide, strong and attaches to vertebrae as
well as discs (prevents hyperextension)
Posterior longitudinal ligament: narrow and relatively weak, attaching only
to discs
*
Note “intervertebral foramen” vs “vertebral foramen” on next slides
Structure of a typical vertebra
Cervical vertebrae (C1-C7)
C1 (atlas)
C2 (axis)
Cervical Vertebrae






Smallest
Lightest
Most flexible
Triangular vertebral
foramen
Transverse
processes have
foramina
(transverse
foramen)
Spinous process
bifid (forked) except
for C7
Thoracic Vertebrae T1-T12




Heart shaped
body
Additional small
costal facets
(costal=ribs)
Round or oval
vertebral
foramen
Form posterior
part of rib cage
Lumbar Vertebrae L1-L5
Massive
blocklike
bodies
 Short, thick
hatchet-shaped
spinous
processes
 Limited mobility

Shapes posterior wall of pelvis
The Sacrum Composite bone of 5 fused vertebrae
Sacral foramina allow passage of vessels & nerves
Coccyx
(the tailbone)
Remember that the
Axial skeleton includes:
Skull
Vertebral column
Thoracic cage
Axial skeleton is shown in green
The Thoracic Cage
Sternum
Ribs

Manubrium

True ribs 1-7

Body

False ribs 8-12

Xiphoid process

Floating ribs 11,12
Vertebral and Sternal Articulations
Typical rib
Disorders of the axial skeleton

Scoliosis (over 10% curvature)

Kyphosis

Lordosis

Vertebral compression fractures

Spinal stenosis
Fontanels





Unossified remnants of
membranes
Present at birth
Anterior fontanel largest
Called “soft spots”
Ossify by 1 ½ - 2 years
Continue to ossify into
adulthood; the sutures can
become fused in old age
Some abnormalities (early fusion) of
sutures: “craniosynostosis”
Metopic Synostosis and trigonocephaly
A: Preop
B: 2 years after
frontal orbital
advancement
Sagittal synostosis and scaphocephaly
The most common suture to fuse is the middle or sagittal suture. Often the
back or front of the skull will be worse but the overall shape is a long skull
with a shortened distance from ear to ear.
Pre-op
CAT scan
Diagram of
surgery
2 years post-op
From - http://www.ppsca.com/skull.htm