The document summarizes key aspects of the axial skeleton, including: 1. The axial skeleton consists of the skull, vertebral column, and thoracic cage. It forms the central axis of the body. 2. The skull is made up of multiple cranial and facial bones that protect the brain and house sensory organs. It includes prominent features like the foramen magnum, cranial fossae, and sutures. 3. The vertebral column consists of 33 vertebrae that fuse into 24 bones in adulthood. It includes cervical, thoracic, lumbar, sacral and coccygeal regions with characteristic features. 4. The thoracic cage is formed from ribs, sternum and

1. The Axial Skeleton
By- Dr. Armaan SinghBy- Dr. Armaan Singh

2. 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?

3. http://homepage.smc.edu/wissmann_paul/bones/EBbonestutorial.html
This is an example of
Prof Wissman’s bone
site; this doesn’t show
the roll-over answers

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

6. Axial skeleton
Skull
Vertebral column
Thoracic cage
Axial skeleton is shown in green

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

10. Cranial bones
parietal parietal
frontal
temporal
parietal
occipital
_______sphenoid
_____ethmoid
occipital

11. Temporal bones
this is the right temporal bone
looking at it from the right side

12. Sphenoid
EthmoidSmall cranial bones…

13. 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)

14. Find: coronal, squamous and lamboid sutures

15. Find: sagittal and lambdoid sutures

16.  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

17. 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

18. Facial bones
 Mandible
 Vomer
 Maxillae (paired)
 Zygomatics (paired)
 Nasal (paired)
 Lacrimal (paired)
 Palatines (paired)
 Inferior nasal conchae (paired)

19. Mandible
Vomer
Maxillae (paired)
Zygomatics (paired)
Nasal (paired)
Lacrimal (paired)
Palatines (paired)
Inferior nasal conchae
(paired)
Facial bones:

26. Mandible (lower jaw)
Maxilla (there are 2 which
fuse, forming the upper jaw)

27. 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
vomer
inf nasal concha
(part of slide 18)
maxilla___________

28. 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

29. 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)

30. Paranasal sinuses
 Air-filled sacs in the bones
 “Paranasal” because they cluster around
and connect to the nasal cavity

31. 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

32. Remember that the
Axial skeleton includes:
Skull
Vertebral column
Thoracic cage
Axial skeleton is shown in green

33. 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)

34. Vertebrae
 Cervical – 7
 Thoracic - 12
 Lumbar - 5
 Sacrum (5 fused)
 Coccyx (4 fused)

35. 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

37. Abnormal curvatures

38. Non-bony parts
 Intervertebral
discs
 anulus fibrosis
and nucleus
pulposus)
 Anterior
longitudinal
ligament
 Posterior
longitudinal
ligament
 Ligamentum
flavum

39. 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
*

40. Structure of a typical vertebra

41. Cervical vertebrae (C1-C7)
C1 (atlas)
C2 (axis)

42.  Smallest
 Lightest
 Most flexible
 Triangular vertebral
foramen
 Transverse
processes have
foramina
(transverse
foramen)
 Spinous process
bifid (forked) except
for C7
Cervical Vertebrae

43.  Heart shaped
body
 Additional small
costal facets
(costal=ribs)
 Round or oval
vertebral
foramen
 Form posterior
part of rib cage
Thoracic Vertebrae T1-T12

44.  Massive
blocklike
bodies
 Short, thick
hatchet-shaped
spinous
processes
 Limited mobility
Lumbar Vertebrae L1-L5

45. The Sacrum
Shapes posterior wall of pelvis
Composite bone of 5 fused vertebrae
Sacral foramina allow passage of vessels & nerves
Coccyx
(the tailbone)

46. Remember that the
Axial skeleton includes:
Skull
Vertebral column
Thoracic cage
Axial skeleton is shown in green

47. The Thoracic Cage

48. Sternum Ribs
 Manubrium
 Body
 Xiphoid process
 True ribs 1-7
 False ribs 8-12
 Floating ribs 11,12

49. Vertebral and Sternal Articulations

50. Typical rib

52. Disorders of the axial skeleton
 Scoliosis (over 10% curvature)
 Kyphosis
 Lordosis
 Vertebral compression fractures
 Spinal stenosis

53. 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

54. Some abnormalities (early fusion) of
sutures: “craniosynostosis”
Metopic Synostosis and trigonocephaly
A: Preop
B: 2 years after
frontal orbital
advancement
Pre-op CAT scan
Diagram of
surgery
2 years post-op
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.
From - http://www.ppsca.com/skull.htm