1. The Axial Skeleton

2. Divisions of the Skeleton
Axial skeleton – skull, vertebrae, and bony thorax
Appendicular skeleton – bones of the arms and legs, including their associated girdles

3. The Axial Skeleton
Figure 5.6a

4. The Axial Skeleton
Figure 5.6b

5. The Skull Two sets of bones Bones are joined by sutures
Cranium
Facial bones
Bones are joined by sutures
Only the mandible is attached by a freely movable joint
Consists of 22 bones interlocked along sutures (all except the mandible)
8 bones make up the cranium
14 bones make up the facial skeleton
Mandible = lower jawbone; only movable bone held to the cranium by ligaments
Orbit of the eye is formed by cranial and facial bones

6. The Cranium Encloses and protects the brain
Surface provides attachments for muscles involved in chewing and head movements
Does not include the mandible

7. Sinuses Air-filled cavities of the cranium Lined with mucous membranes
All connected by passageways to the nasal cavity
Function to reduce the weight of the skull and increase voice intensity and resonance

8. Paranasal Sinuses
Hollow portions of bones surrounding the nasal cavity
Functions of paranasal sinuses
Lighten the skull
Give resonance and amplification to voice

9. Paranasal Sinuses
Figure 5.10a

10. Paranasal Sinuses
Figure 5.10b

11. Cranial Bones Frontal bone Parietal bones (2) Occipital bone
Temporal bones (2)
Sphenoid bone
Ethmoid bone

12. Human Skull, Lateral View
Figure 5.7

13. Frontal Bone Features Frontal sinuses
Develops in 2 parts that grow together by 5-6 years old

14. Parietal Bone Features
Sagittal suture
Coronal suture

15. Occipital Bone Features
Lambdoidal suture
Joins parietal bones to the occipital
Foramen magnum
”Large Hole”
Occipital condyles
Rest on the first vertebra

16. Human Skull, Inferior View
Figure 5.9

17. Temporal Bone Features
Squamosal suture
temporal to parietal
External auditory meatus
ear canal
Mandibular fossae
joint with mandible
Mastoid process
neck muscle attachment
Contains mastoid sinuses
Styloid process
below EAM, anchors muscles of tongue and pharynx
Zygomatic process
helps form cheek prominence

18. Sphenoid Bone Features
Wedged between several other bones in anterior portion of the cranium
2 winglike structures extend laterally toward each side of the skull
Sella turcica – houses pituitary gland
Sphenoidal sinuses

19. Ethmoid Bone Features Located in front of the sphenoid bone
Consists of 2 masses on each side of the nasal cavity
Cribriform plates
Holey areas that allow nerve fibers from the nose to reach the brain.
Superior and middle nasal conchae
support mucous membranes of the nose
Ethmoid sinuses
Crista galli
triangular process that projects upward from the cribriform plates; place of attachment for membranes around the brain

20. Human Skull, Superior View
Figure 5.8

21. Facial Skeleton 13 immovable bones + the mandible
Provides attachments for muscles for facial expressions and jaw movements

22. Bones of the Facial Skeleton
Maxillary bones (2)
Palatine bones (2)
Zygomatic bones (2)
Lacrimal bones (2)
Nasal bones (2)
Vomer bone
Inferior nasal conchae (2)
Mandible

23. Maxillary Bone Features
Form upper jaw
All other immovable facial bones articulate with them
Hard palate
Sockets of upper teeth
Maxillary sinuses
Palatine processes
where the maxillary bones meet

24. Palatine Bone Features
L-shaped bones behind the maxillae
Posterior hard palate

25. Zygomatic Bone
Prominences of the cheeks
Commonly called check bones

26. Lacrimal Bone Features
Thin, scalelike bones between the ethmoid bone and maxillae in the medial walls of the orbits
Groove in anterior portion provides pathway for tears

27. Nasal Bone Features
Form the bridge of the nose

28. Vomer Bone Features Forms most of the boney nasal septum
Vomer means “plow” and refers to the shape of the bone.

29. Inferior Nasal Conchae Features
Scroll-shaped bones attached to lateral walls of the nasal cavity
Support mucous membranes of the nose

30. Mandible Features Only free moving bone of the face
Largest and strongest bone of the face
Parts of the Mandible
Ramus
attachment for large chewing muscles
Mandibular condyle
articulates with mandibular fossae of temporal bones
Alveolar border
houses lower tooth sockets
Mandibular foramen
carries nerves and blood vessels to the lower teeth; dental injection site
Mental foramen
– carries branches of nerves and blood vessels of the mandibular foramen

31. The Hyoid Bone
The only bone that does not articulate with another bone
Serves as a moveable base for the tongue
Aids in swallowing and speech

32. The Fetal Skull
The fetal skull is large compared to the infant’s total body length
Fontanels (flexible)
fibrous membranes connecting the cranial bones
Allow the brain to grow
Convert to bone within 24 months after birth

33. The Vertebral Column
Each vertebrae is given a name according to its location
There are 24 single vertebral bones separated by intervertebral discs
Seven cervical vertebrae are in the neck
Twelve thoracic vertebrae are in the chest region
Five lumbar vertebrae are associated with the lower back

34. The Vertebral Column Nine vertebrae fuse to form two composite bones
Sacrum
Coccyx

35. Functions of the Vertebral Column
Supports the head and trunk
Permits movement
Protects the spinal cord which passes through the vertebral canal

36. The Vertebral Column The spine has a normal curvature
Primary curvatures are the spinal curvatures of the thoracic and sacral regions
Present from birth
Secondary curvatures are the spinal curvatures of the cervical and lumbar regions
Develop after birth

37. Typical Vertebra Body Intervertebral disks Pedicles Laminae
thick, drum-shaped, anterior portion of bone
Intervertebral disks
cushion and soften forces caused by movements
Pedicles
2 short stalks that project posteriorly from each vertebral body
Laminae
2 plates that arise from pedicles to fuse and form the spinous process
Transverse processes
between the pedicles and laminae; project laterally and posteriorly

38. Typical Vertebra continued…
Vertebral arch
formed by the pedicles, laminae, and spinous process; around the vertebral foramen
Vertebral foramen
opening through which the spinal cord passes
Intervertebral foramina
passageways for spinal nerves; between adjacent vertebrae

39. Cervical Vertebrae 7 vertebrae Make up the neck region
Smallest vertebrae
Denser bone tissues than the other regions
Distinctive because they have transverse foramina (passageways for arteries leading to the brain)
Spinous processes are uniquely forked (C2-C6)
C7 = vertebrae prominens; spinous process is longer and protrudes beyond the other cervical vertebrae

40. Atlas C1 Supports the head Has no body or spine
Consists of a bony ring with 2 transverse processes
Facets – kidney-shaped areas on the superior surface that articulate with the occipital condyles

41. Axis C2 Vertebrae associated with hangman’s fracture
Dens – tooth-like process that projects upward and lies in the ring of the atlas
As the head is turned from side to side, the atlas pivots around the dens.

42. Thoracic Vertebrae 12 in number Larger than cervical vertebrae
Long, pointed spinous process which slopes downward
Facets on sides of vertebral body articulate with the ribs
Bodies of the vertebrae increase in size from T3 down
can bear an increasing load of body weight

43. Lumbar Vertebrae 5 in number Located in the small of the back
Larger, stronger, and support more weight than the others
Transverse processes project posteriorly at sharp angles
Short, thick spinous processes are nearly horizontal

44. Sacrum Triangular structure at the base of the vertebral column
5 vertebrae fuse to form the sacrum between years of age
Fused spinous processes form a ridge of tubercles called the median sacral crest
Dorsal sacral foramina – openings to the sides of the tubercles through which nerves and blood vessels pass
Sacral canal – formed from vertebral foramina and opens at the sacral hiatus

45. Coccyx Tailbone Lowest part of the vertebral column
Made of 4 vertebrae that fuse by the 25th year
Acts as a shock absorber when sitting

46. Vertebral Column Disorders
Ruptured/herniated disk
outer layers of the intervertebral disk are broken and the central mass of the disk is squeezed out from extra pressure, pressing on the spinal cord and spinal nerves
pain, numbness, loss of muscular function

47. Curvature Disorders of the Spine
Kyphosis – hunchback; exaggerated thoracic curvature
Scoliosis – abnormal lateral curvature
Lordosis – swayback; exaggerated lumbar curvature

48. Scoliosis Repair

49. Thoracic Cage
Includes ribs, thoracic vertebrae, sternum, and costal cartilages
Supports the shoulder girdle and upper limbs
Protects viscera
Plays a role in breathing

50. Ribs 12 pair – one pair for each vertebra
True ribs – 1st 7 rib pairs; join the sternum directly by costal cartilages (hyaline)
False ribs – bottom 5 rib pairs; do not join the sternum directly
Cartilages of the upper 3 false ribs join the cartilage of the 7th rib
Floating ribs – last 2 rib pairs; no attachment to the sternum

51. Sternum Breastbone Develops in 3 parts:
Manubrium – articulates with clavicles at clavicular notches
Body – fuses to manubrium at middle age at the sternal angle
Xiphoid process – begins as cartilage, slowly ossifies, and fuses to the body at middle age
Red bone marrow in sternum produces RBCs into adulthood