4. 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
5. ■ 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
7. 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
8. 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)
9. Cranial bones
■ Frontal bone
■ Parietal bones (paired)
■ Occipital bone
■ Temporal bones (paired)
■ Sphenoid bone
■ Ethmoid bone
16. Some abnormalities (early fusion)
of sutures: “craniosynostosis”
• Metopic Synostosis and trigonocephaly
• A: Preop
•B: 2 years
after frontal
orbital
advanceme
nt
• 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
18. 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
28. Nasal cavity
■ 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
nasal bone
ethmoid
inf nasal concha
vomer
(part of slide 18)
maxilla
29. 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
30. Orbit
Cone-shaped bony cavities holding the eyes,
muscles that move the eyes, some fat and tear-
producing 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)
31. Paranasal sinuses
■ Air-filled sacs in the bones
■ “Paranasal” because they cluster around
and connect to the nasal cavity
32. 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
33. Remember that the Axial
skeleton includes:
Skull
Vertebral column
Thoracic cage
Axial skeleton is shown in green
34. 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)
36. 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
40. 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
*
44. ■ Heart shaped
body
■ Additional small
costal facets
(costal=ribs)
■ Round or oval
vertebral
foramen
■ Form posterior
part of rib cage
Thoracic Vertebrae T1-
T12
46. Shapes posterior wall of pelvis
The Sacrum Composite bone of 5 fused vertebrae
Sacral foramina allow passage of vessels & nerves
Coccyx
(the tailbone)
47. Remember that the Axial
skeleton includes:
Skull
Vertebral column
Thoracic cage
Axial skeleton is shown in green
56. 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
57. I highly recommend Professor Wissman’s
sites
■ For bones:
http://homepage.smc.edu/wissmann_paul/bones/EBbonestuto
■ 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
