1. Bones, Part 1: The Axial Skeleton

2. Composed of 206 named bones grouped into two divisions
The Skeleton
Consists of
Bones, cartilage, joints, and ligaments
Composed of 206 named bones grouped into two divisions
Axial skeleton (80 bones)
Appendicular skeleton (126 bones)
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3. Formed from 80 named bones
The Axial Skeleton
Formed from 80 named bones
Consists of skull, vertebral column, and bony thorax
Figure 7.1a
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4. The Axial Skeleton Figure 7.1b
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5. Projections that provide attachment for muscles and ligaments
Bone Markings
Projections that provide attachment for muscles and ligaments
Projections that help form joints
Depressions and openings for passage of nerves and blood vessels
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6. Formed by cranial and facial bones
The Skull
Formed by cranial and facial bones
Figure 7.2a
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7. The Cranium The cranium serves to Enclose brain
Provide attachment sites for some head and neck muscles
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8. The Face Facial bones serve to Form framework of the face
Form cavities for the sense organs of sight, taste, and smell
Provide openings for the passage of air and food
Hold the teeth in place
Anchor muscles of the face
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9. Overview of Skull Geography
Facial bones form anterior aspect
Cranium is divided into cranial vault and the base
Internally, prominent bony ridges divide skull into distinct fossae
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10. Overview of Skull Geography
The skull contains smaller cavities
Middle and inner ear cavities – in lateral aspect of cranial base
Nasal cavity – lies in and posterior to the nose
Orbits – house the eyeballs
Air-filled sinuses – occur in several bones around the nasal cavity
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11. Overview of Skull Geography
The skull contains approximately 85 named openings
Foramina, canals, and fissures
Provide openings for important structures
Spinal cord
Blood vessels serving the brain
12 pairs of cranial nerves
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12. Formed from eight large bones
Cranial Bones
Formed from eight large bones
Paired bones include
Temporal bones
Parietal bones
Unpaired bones include
Frontal bone
Occipital bone
Sphenoid bone
Ethmoid bone
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13. Forms the forehead and roofs of the orbits Forms superciliary arches
Frontal Bones
Forms the forehead and roofs of the orbits
Forms superciliary arches
Internally, it contributes to the anterior cranial fossa
Contains frontal sinuses
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14. Parietal Bones and Sutures
Parietal bones form superior and lateral parts of skull
Four sutures of the cranium
Coronal suture – runs in the coronal plane
Located where parietal bones meet the frontal bone
Squamous suture – occurs where each parietal bone meets a temporal bone inferiorly
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15. Parietal Bones and Sutures
Sutures of the cranium (continued)
Sagittal suture – occurs where right and left parietal bones meet superiorly
Lambdoid suture – occurs where the parietal bones meet the occipital bone posteriorly
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16. Small bones that occur within sutures
Sutural Bones
Small bones that occur within sutures
Irregular in shape, size, and location
Not all people have sutural bones
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17. The Skull – Posterior View
Figure 7.2b
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18. Forms the posterior portion of the cranium and cranial base
Occipital Bone
Forms the posterior portion of the cranium and cranial base
Articulates with the temporal bones and parietal bones
Forms the posterior cranial fossa
Foramen magnum located at its base
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19. Features and structures
Occipital Bone
Features and structures
Occipital condyles
Hypoglossal foramen
External occipital protuberance
Superior nuchal lines
Inferior nuchal lines
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20. Inferior Aspect of the Skull
Figure 7.4a
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21. Lie inferior to parietal bones
Temporal Bones
Lie inferior to parietal bones
Form the inferolateral portion of the skull
Term “temporal”
Comes from Latin word for time
Specific regions of temporal bone
Squamous, temporal, petrous, and mastoid regions
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22. Lateral Aspect of the Skull
Figure 7.3a
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23. The Temporal Bone Figure 7.5
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24. Bones, Part 1: The Axial Skeleton

25. Spans the width of the cranial floor Resembles a butterfly or bat
The Sphenoid Bone
Spans the width of the cranial floor
Resembles a butterfly or bat
Consists of a body and three pairs of processes
Contains five important openings
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26. The Sphenoid Bone Figure 7.6a
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27. The Sphenoid Bone Figure 7.6b
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28. Lies between nasal and sphenoid bones
The Ethmoid Bone
Lies between nasal and sphenoid bones
Forms most of the medial bony region between the nasal cavity and orbits
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29. The Ethmoid Bone Figure 7.7
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30. Bones of the Skull Table 7.1 (1 of 2)
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31. Facial Bones Unpaired bones Paired bones Mandible and vomer Maxillae
Zygomatic bones
Nasal bones
Lacrimal bones
Palatine bones
Inferior nasal conchae
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32. The lower jawbone is the largest and strongest facial bone
Mandible
The lower jawbone is the largest and strongest facial bone
Composed of two main parts
Horizontal body
Two upright rami
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33. Mandible
Figure 7.8a
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34. Articulate with all other facial bones except the mandible
Maxillary Bones
Articulate with all other facial bones except the mandible
Contain maxillary sinuses – largest paranasal sinuses
Forms part of the inferior orbital fissure
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35. Maxillary Bones Figure 7.8b
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36. Maxillary Bones Figure 7.4a
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37. Other Bones of the Face Zygomatic bones Nasal bones Lacrimal bones
Form lateral wall of orbits
Nasal bones
Form bridge of nose
Lacrimal bones
Located in the medial orbital walls
Palatine bones
Complete the posterior part of the hard palate
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38. Inferior nasal conchae
Other Bones of the Face
Vomer
Forms the inferior part of the nasal septum
Inferior nasal conchae
Thin, curved bones that project medially form the lateral walls of the nasal cavity
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39. Facial Bones Table 7.1 (2 of 2)
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40. Bones, Part 1: The Axial Skeleton

41. Bones of the Face Figure 7.2a
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42. Special Parts of the Skull
Orbits
Nasal cavity
Paranasal sinuses
Hyoid bone
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43. Nasal Cavity
Figure 7.9a
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44. Nasal Septum
Figure 7.9b
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45. Orbits
Figure 7.10b
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46. Air-filled sinuses are located within
Paranasal Sinuses
Air-filled sinuses are located within
Frontal bone
Ethmoid bone
Sphenoid bone
Maxillary bones
Lined with mucous membrane
Serve to lighten the skull
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47. Paranasal Sinuses Figure 7.11a, b
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48. Bones, Part 1: The Axial Skeleton

49. Lies inferior to the mandible
The Hyoid Bone
Lies inferior to the mandible
The only bone with no direct articulation with any other bone
Acts as a movable base for the tongue
Figure 7.12
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50. Formed from 26 bones in the adult
The Vertebral Column
Formed from 26 bones in the adult
Transmits weight of trunk to the lower limbs
Surrounds and protects the spinal cord
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51. Serves as attachment sites for muscles of the neck and back
The Vertebral Column
Serves as attachment sites for muscles of the neck and back
Held in place by ligaments
Anterior and posterior longitudinal ligaments
Ligamentum flavum
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52. The Vertebral Column Figure 7.13
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53. Cushion-like pads between vertebrae Act as shock absorbers
Intervertebral Discs
Cushion-like pads between vertebrae
Act as shock absorbers
Compose about 25% of height of vertebral column
Composed of
Nucleus pulposus and annulus fibrosis
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54. Intervertebral Discs Nucleus pulposus
The gelatinous inner sphere of intervertebral disc
Enables spine to absorb compressive stresses
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55. Intervertebral Discs Annulus fibrosis
An outer collar of ligaments and fibrocartilage
Contains the nucleus pulposus
Functions to bind vertebrae together, resist tension on the spine, and absorb compressive forces
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56. Ligaments and Intervertebral Discs
Figure 7.14a
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57. May be caused by trauma to the spine
Herniated Disc
May be caused by trauma to the spine
Aging is also a contributing factor
Nucleus pulposes loses cushioning properties
Anulus fibrosis weakens
Figure 7.14c
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58. Regions and Normal Curvatures
Vertebral column is about 70 cm (28 inches)
Vertebral column is divided into five major regions
Cervical vertebrae
7 vertebrae of the neck region
Thoracic vertebrae
12 vertebrae of the thoracic region
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59. Regions and Normal Curvatures
Vertebral column is divided into five major regions (continued)
Lumbar vertebrae
5 vertebrae of the lower back
Sacrum
Inferior to lumbar vertebrae
Articulates with coxal bones
Coccyx
Most inferior region of the vertebral column
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60. Regions and Normal Curvatures
Four distinct curvatures give vertebral column an S-shape
Cervical and lumbar curvature
Are concave posteriorly
Thoracic and sacral curvatures
Are convex posteriorly
Curvatures increase the resilience of the spine
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61. Regions and Normal Curvatures
PLAY
Spine (vertical)
Figure 7.13
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62. General Structure of Vertebrae
PLAY
Spine (horizontal)
Figure 7.15
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63. Bones, Part 1: The Axial Skeleton

64. Regions Vertebral Characteristics
Specific regions of the spine perform specific functions
Types of movement that occur between vertebrae
Flexion and extension
Lateral flexion
Rotation in the long axis
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65. Seven cervical vertebrae (C1 – C7) – smallest and lightest vertebrae
C3 – C7 are typical cervical vertebrae
Body is wider laterally
Spinous processes are short and bifid (except C7)
Vertebral foramen are large and triangular
Transverse processes contain transverse foramina
Superior articular facets face superoposteriorly
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66. Cervical Vertebrae Table 7.2a
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67. Cervical Vertebrae Figure 7.17a
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68. Lacks a body and spinous process Supports the skull
The Atlas
C1 is termed the atlas
Lacks a body and spinous process
Supports the skull
Superior articular facets receive the occipital condyles
Allows flexion and extension of neck
Nodding the head “yes”
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69. The Atlas
Figure 7.16a
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70. The Atlas
Figure 7.16b
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71. Has a body and spinous process
The Axis
Has a body and spinous process
Dens (odontoid process) projects superiorly
Formed from fusion of the body of the atlas with the axis
Acts as a pivot for rotation of the atlas and skull
Participates in rotating the head from side to side
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72. The Axis
Figure 7.16c
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73. Bones, Part 1: The Axial Skeleton

74. Thoracic Vertebrae (T1 – T12)
All articulate with ribs
Have heart-shaped bodies from the superior view
Each side of the body of T1 – T10 bears demifacts for articulation with ribs
T1 has a full facet for the first rib
T10 – T12 only have a single facet
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75. Thoracic Vertebrae Table 7.2b
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76. Spinous processes are long and point inferiorly
Thoracic Vertebrae
Spinous processes are long and point inferiorly
Vertebral foramen are circular
Transverse processes articulate with tubercles of ribs
Superior articular facets point posteriorly
Inferior articular processes point anteriorly
Allows rotation and prevents flexion and extension
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77. Lumbar Vertebrae (L1 – L5)
Bodies are thick and robust
Transverse processes are thin and tapered
Spinous processes are thick, blunt, and point posteriorly
Vertebral foramina are triangular
Superior and inferior articular facets directly medially
Allows flexion and extension – rotation prevented
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78. Lumbar Vertebrae Table 7.2c
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79. Lumbar Vertebrae Figure 7.17c
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80. Shapes the posterior wall of pelvis Formed from 5 fused vertebrae
Sacrum (S1 – S5)
Shapes the posterior wall of pelvis
Formed from 5 fused vertebrae
Superior surface articulates with L5
Inferiorly articulates with coccyx
Sacral promontory
Where the first sacral vertebrae bulges into pelvic cavity
Center of gravity is 1 cm posterior to sacral promontory
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81. Sacrum Sacral foramina Ventral foramina Dorsal foramina
Passage for ventral rami of sacral spinal nerves
Dorsal foramina
Passage for dorsal rami of sacral spinal nerves
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82. Sacrum
Figure 7.18a, b
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83. Formed from 3 – 5 fused vertebrae
Coccyx
Is the “tailbone”
Formed from 3 – 5 fused vertebrae
Offers only slight support to pelvic organs
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84. Bones, Part 1: The Axial Skeleton

85. Forms the framework of the chest Components of the bony thorax
Thoracic vertebrae – posteriorly
Ribs – laterally
Sternum and costal cartilage – anteriorly
Protects thoracic organs
Supports shoulder girdle and upper limbs
Provides attachment sites for muscles
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86. The Bony Thorax Figure 7.19a
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87. The Bony Thorax Figure 7.19b
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88. Formed from three sections
Sternum
Formed from three sections
Manubrium – superior section
Articulates with medial end of clavicles
Body – bulk of sternum
Sides are notched at articulations for costal cartilage of ribs 2–7
Xiphoid process – inferior end of sternum
Ossifies around age 40
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89. Sternum Anatomical landmarks Jugular notch Sternal angle
Central indentation at superior border of the manubrium
Sternal angle
A horizontal ridge where the manubrium joins the body
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90. All ribs attach to vertebral column posteriorly
True ribs - superior seven pairs of ribs
Attach to sternum by costal cartilage
False ribs – inferior five pairs of ribs
Ribs 11–12 are known as floating ribs
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91. Ribs
Figure 7.20a
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92. Ribs
Figure 7.20b
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93. Disorders of the Axial Skeleton
Abnormal spinal curvatures
Scoliosis – an abnormal lateral curvature
Kyphosis – an exaggerated thoracic curvature
Lordosis – an accentuated lumbar curvature – “swayback”
Stenosis of the lumbar spine
A narrowing of the vertebral canal
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94. The Axial Skeleton Throughout Life
Membrane bones begin to ossify in second month of development
Bone tissue grows outward from ossification centers
Fontanels
Unossified remnants of membranes
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95. Fontanels
Figure 7.21a
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96. Fontanels
Figure 7.21b
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97. The Axial Skeleton Throughout Life
Many bones of the face and skull form by intramembranous ossification
Endochondral bones of the skull
Occipital bone
Sphenoid
Ethmoid bones
Parts of the temporal bone
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98. The Axial Skeleton Throughout Life
Curvatures of the vertebral column
Primary curvatures – thoracic and sacral curvatures
An infant's spine is C-shaped at birth
Secondary curvatures – cervical and lumbar curvatures
Develop when a baby begins to walk
Redistributes weight of the upper body over the lower limbs
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99. The Axial Skeleton Throughout Life
Aging of the axial skeleton
Water content of the intervertebral discs decreases
By age 55, loss of a few centimeters in height is common
Thorax becomes more rigid
Bones lose mass with age
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