1. 7
The Skeleton: Part A

2. The Axial Skeleton Consists of 80 bones Three major regions Skull
Vertebral column
Thoracic cage

3. Cranium Skull Facial bones Clavicle Thoracic cage Scapula (ribs and
sternum)
Scapula
Sternum
Rib
Humerus
Vertebra
Vertebral
column
Radius
Ulna
Sacrum
Carpals
Phalanges
Metacarpals
Femur
Patella
Tibia
Fibula
Tarsals
Metatarsals
(a) Anterior view
Phalanges
Figure 7.1a

4. *Ligaments – connect bone to bone Tendons – connect muscle to bone

5. *Vertebral Column Transmits weight of trunk to lower limbs
Surrounds and protects spinal cord
Flexible curved structure containing 26 irregular bones (vertebrae)
Cervical vertebrae (7)—vertebrae of the neck
Thoracic vertebrae (12)—vertebrae of the thoracic cage
Lumbar vertebrae (5)—vertebra of the lower back
Sacrum—bone inferior to the lumbar vertebrae
Coccyx—terminus of vertebral column

6. *Vertebral Column: Curvatures
Increase the resilience and flexibility of the spine
Two posteriorly concave curvatures
Cervical and lumbar
Two posteriorly convex curvatures
Thoracic and sacral
Abnormal spine curvatures
Scoliosis (abnormal lateral curve)
Kyphosis (hunchback)
Lordosis (swayback)

7. Figure 7.16 C1 Cervical curvature (concave) 7 vertebrae, C1–C7 Spinous
process
Transverse
processes
Thoracic
curvature
(convex)
12 vertebrae,
T1–T12
Intervertebral
discs
Intervertebral
foramen
Lumbar curvature
(concave)
5 vertebrae, L1–L5
Sacral curvature
(convex)
5 fused vertebrae
sacrum
Coccyx
4 fused vertebrae
Anterior view
Right lateral view
Figure 7.16

8. *Developmental Aspects: Spinal Curvature
Thoracic and sacral curvatures are obvious at birth
These primary curvatures give the spine a C shape
Convex posteriorly

9. Figure 7.37

10. *Developmental Aspects: Spinal Curvature
Secondary curvatures
Cervical and lumbar—convex anteriorly
Appear as child develops (e.g., lifts head, learns to walk)

11. *Developmental Aspects: Old Age
Intervertebral discs become thin, less hydrated, and less elastic
Risk of disc herniation increases
Loss of stature by several centimeters is common by age 55
Costal cartilages ossify, causing the thorax to become rigid
All bones lose mass

12. *Intervertebral Discs
Cushionlike pad composed of two parts
Nucleus pulposus
Inner gelatinous nucleus that gives the disc its elasticity and compressibility
Anulus fibrosus
Outer collar composed of collagen and fibrocartilage

13. Supraspinous ligament
Intervertebral
disc
Supraspinous ligament
Transverse process
Anterior
longitudinal
ligament
Sectioned
spinous process
Intervertebral foramen
Ligamentum flavum
Posterior longitudinal
ligament
Interspinous
ligament
Anulus fibrosus
Nucleus pulposus
Inferior articular process
Sectioned body
of vertebra
Median section of three vertebrae, illustrating the composition of the discs and the ligaments
Figure 7.17a

14. Vertebral spinous process (posterior aspect of vertebra)
Spinal cord
Spinal nerve root
Transverse
process
Herniated portion
of disc
Anulus fibrosus
of disc
Nucleus
pulposus
of disc
(c) Superior view of a herniated intervertebral disc
Figure 7.17c

15. General Structure of Vertebrae
Body or centrum
Anterior weight-bearing region
Vertebral arch
Composed of pedicles and laminae that, along with centrum, enclose vertebral foramen
Vertebral foramina
Together make up vertebral canal for spinal cord
Intervertebral foramina
Lateral openings between adjacent vertebrae for spinal nerves

16. General Structure of Vertebrae
Seven processes per vertebra:
Spinous process—projects posteriorly
Transverse processes (2)—project laterally
Superior articular processes (2)—protrude superiorly inferiorly
Inferior articular processes (2)—protrude inferiorly
PLAY
Animation: Rotatable Spine (horizontal)
PLAY
Animation: Rotatable Spine (vertical)

17. Posterior Vertebral Lamina arch Spinous Transverse process process
Superior
articular
process
and
facet
Vertebral
foramen
Pedicle
Body
(centrum)
Anterior
Figure 7.18

18. C1 to C7: smallest, lightest vertebrae
Cervical Vertebrae
C1 to C7: smallest, lightest vertebrae
C3 to C7 share the following features
Oval body
Spinous processes are bifid (except C7)
Large, triangular vertebral foramen
Transverse foramen in each transverse process

19. Table 7.2

20. (a) Cervical vertebrae
Dens of axis
Transverse ligament
of atlas
C1 (atlas)
C2 (axis) C3
Inferior articular
process
Bifid spinous
process
Transverse processes
C7 (vertebra
prominens)
(a) Cervical vertebrae
Figure 7.20a

21. C1 (atlas) and C2 (axis) have unique features Atlas (C1)
Cervical Vertebrae
C1 (atlas) and C2 (axis) have unique features
Atlas (C1)
No body or spinous process
Consists of anterior and posterior arches, and two lateral masses
Superior surfaces of lateral masses articulate with the occipital condyles

22. (a) Superior view of atlas (C1) (b) Inferior view of atlas (C1)
Posterior
Posterior
Posterior
tubercle
Posterior
tubercle
Posterior arch
Posterior arch
Inferior
articular
facet
Lateral
masses
Transverse
process
Lateral
masses
Transverse
foramen
Superior
articular
facet
Transverse
foramen
Anterior
arch
Anterior
tubercle
Anterior arch
Facet for dens
Anterior tubercle
(a) Superior view of atlas (C1)
(b) Inferior view of atlas (C1)
Figure 7.19a-b

23. Cervical Vertebrae Axis (C2)
Dens projects superiorly into the anterior arch of the atlas
Dens is a pivot for the rotation of the atlas

24. (c) Superior view of axis (C2)
Posterior C2
Spinous process
Lamina
Inferior
articular
process
Pedicle
Superior
articular
facet
Transverse
process
Dens
Body
(c) Superior view of axis (C2)
Figure 7.19c

25. Thoracic Vertebrae
T1 to T12
All articulate with ribs at facets and demifacets
Long spinous process
Location of articular facets allows rotation of this area of spine

26. Table 7.2

27. (b) Thoracic vertebrae
Superior articular
process
Transverse
process
Transverse
costal facet (for
tubercle of rib)
Intervertebral
disc
Body
Inferior costal
facet (for head
of rib)
Spinous
process
Inferior articular
process
(b) Thoracic vertebrae
Figure 7.20b

28. Lumbar Vertebrae
L1 to L5
Short, thick pedicles and laminae
Flat hatchet-shaped spinous processes
Orientation of articular facets locks lumbar vertebrae together so as to prevent rotation

29. Table 7.2

30. Superior articular process Transverse Body process Intervertebral disc
Inferior
articular
process
Spinous
process
(c) Lumbar vertebrae
Figure 7.20c

31. Sacrum and Coccyx Sacrum Coccyx 5 fused vertebrae (S1–S5)
Forms posterior wall of pelvis
Articulates with L5 superiorly, and with auricular surfaces of the hip bones laterally
Coccyx
Tailbone
3–5 fused vertebrae
Articulates superiorly with sacrum

32. Sacral promontory Ala Body of first sacral vertebra Transverse
ridges (sites
of vertebral
fusion)
Anterior
sacral
foramina
Apex
Coccyx
(a) Anterior view
Figure 7.21a

33. Sacral Facet of Body canal superior Ala articular process Auricular
surface
Median
sacral
crest
Lateral
sacral
crest
Posterior
sacral
foramina
Sacral
hiatus
Coccyx
(b) Posterior view
Figure 7.21b

34. Thoracic Cage Composed of Functions Thoracic vertebrae Sternum
Ribs and their costal cartilages
Functions
Protects vital organs of thoracic cavity
Supports shoulder girdle and upper limbs
Provides attachment sites for many muscles, including intercostal muscles used during breathing

35. Sternum (Breastbone) Three fused bones Manubrium
Articulates with clavicles and ribs 1 and 2
Body
Articulates with costal cartilages of ribs 2 through 7
Xiphoid process
Site of muscle attachment
Not ossified until ~ age 40

36. Ribs and Their Attachments
12 pairs
All attach posteriorly to thoracic vertebrae
Pairs 1 through 7
True (vertebrosternal) ribs
Attach directly to the sternum by individual costal cartilages

37. Ribs and Their Attachments
Pairs 8 through12
False ribs
Pairs 8–10 also called vertebrochondral ribs
Attach indirectly to sternum by joining costal cartilage of rib above
Pairs 11–12 also called vertebral (floating) ribs
No attachment to sternum

38. (a) Skeleton of the thoracic cage, anterior view
Jugular notch
Clavicular notch
Manubrium
Sternal angle
Body
Sternum
True
ribs
(1–7)
Xiphisternal
joint
Xiphoid
process
False
ribs
(8–12)
Intercostal spaces
Costal cartilage
Costal margin L1
Vertebra
Floating ribs (11, 12)
(a) Skeleton of the thoracic cage, anterior view
Figure 7.22a

39. Structure of a Typical Rib
Main parts:
Head
Articulates posteriorly with facets (demifacets) on bodies of two adjacent vertebrae
Neck
Tubercle
Articulates posteriorly with transverse costal facet of same-numbered thoracic vertebra
Shaft

40. Transverse costal facet (for tubercle of rib) Superior costal facet
(for head of rib)
Angle
of rib
Body of vertebra
Head of rib
Intervertebral disc
Neck of rib
Tubercle of rib
Shaft
Sternum
Cross-
section
of rib
Costal groove
Costal cartilage
(a) Vertebral and sternal articulations of a typical true rib
Figure 7.23a

41. Articular facet on tubercle of rib Spinous process Shaft Transverse
costal facet
(for tubercle
of rib)
Ligaments
Neck of rib
Body of
thoracic
vertebra
Head of rib
Superior costal facet
(for head of rib)
(b) Superior view of the articulation between a rib and a thoracic vertebra
Figure 7.23b

42. *Appendicular Skeleton
Bones of the limbs and their girdles
Pectoral girdle attaches the upper limbs to the body trunk
Pelvic girdle secures the lower limbs

43. Pectoral Girdle (Shoulder Girdle)
Clavicles and the scapulae
Attach the upper limbs to the axial skeleton
Provide attachment sites for muscles that move the upper limbs
PLAY
A&P Flix™: Bones of the pectoral girdle

44. Articulated pectoral girdle
Acromio-
clavicular
joint
Clavicle
Scapula
(a)
Articulated pectoral girdle
Figure 7.24a

45. Clavicles (Collarbones)
Flattened acromial (lateral) end articulates with the scapula
Cone-shaped sternal (medial) end articulates with the sternum
Act as braces to hold the scapulae and arms out laterally

46. Right clavicle, superior view
Sternal (medial)
end
Posterior
Anterior
Acromial (lateral)
end
(b)
Right clavicle, superior view
Figure 7.24b

47. Scapulae (Shoulder Blades)
Situated on the dorsal surface of rib cage, between ribs 2 and 7
Flat and triangular, with three borders and three angles
Seven large fossae, named according to location

48. (a) Right scapula, anterior aspect
Acromion
Suprascapular notch
Superior border
Coracoid
process
Superior
angle
Glenoid
cavity
Subscapular
fossa
Lateral border
Medial border
Inferior angle
(a) Right scapula, anterior aspect
Figure 7.25a

49. (b) Right scapula, posterior aspect
Coracoid process
Suprascapular notch
Superior
angle
Acromion
Supraspinous
fossa
Glenoid
cavity
at lateral
angle
Spine
Infraspinous
fossa
Medial border
Lateral border
(b) Right scapula, posterior aspect
Figure 7.25b

50. (c) Right scapula, lateral aspect Inferior angle
Supraspinous fossa
Supraglenoid
tubercle
Acromion
Coracoid
process
Glenoid
cavity
Spine
Supraspinous
fossa
Infraspinous
fossa
Infraglenoid
tubercle
Infraspinous
fossa
Subscapular
fossa
Subscapular
fossa
Posterior
Anterior
(c) Right scapula, lateral aspect
Inferior angle
Figure 7.25c

51. *The Upper Limb
30 bones form the skeletal framework of each upper limb
Arm
Humerus
Forearm
Radius and ulna
Hand
8 carpal bones in the wrist
5 metacarpal bones in the palm
14 phalanges in the fingers

52. Humerus
Largest, longest bone of upper limb
Articulates superiorly with glenoid cavity of scapula
Articulates inferiorly with radius and ulna

53. Greater Head of tubercle humerus Lesser Anatomical tubercle neck
Inter-
tubercular
sulcus
Deltoid
tuberosity
Lateral
supracondylar
ridge
Coronoid
fossa
Radial
fossa
Medial
epicondyle
Capitulum
Trochlea
(a) Anterior view
Figure 7.26a

54. Bones of the Forearm Ulna Radius Medial bone in forearm
Forms the major portion of the elbow joint with the humerus
Radius
Lateral bone in forearm
Head articulates with capitulum of humerus and with radial notch of ulna
Interosseous membrane connects the radius and ulna along their entire length

55. Radial notch of the ulna Olecranon process Trochlear notch Head
Head of
radius
Neck
Coronoid
process
Radial
tuberosity
Neck of
radius
Proximal
radioulnar
joint
Interosseous
membrane
Ulna
Radius
Ulnar notch
of the radius
Radius
Head of ulna
Styloid
process of ulna
Styloid
process
of radius
Distal radioulnar
joint
Styloid process
of radius
(a) Anterior view
(b) Posterior view
Figure 7.27a-b

56. (c) Proximal portion of ulna, lateral view
Olecranon process
View
Trochlear notch
Coronoid process
Radial notch
(c) Proximal portion of ulna,
lateral view
Ulnar notch of radius
Articulation
for lunate
Articulation
for scaphoid
Styloid
process
Head
of ulna
Styloid
process
View
(d) Distal ends of the radius and
ulna at the wrist
Figure 7.27c-d

57. (c) Anterior view at the elbow region
Humerus
Coronoid
fossa
Capitulum
Medial
epicondyle
Head of
radius
Trochlea
Coronoid
process of
ulna
Radial
tuberosity
Radius
Radial notch
Ulna
(c) Anterior view at the elbow region
Humerus
Olecranon
fossa
Olecranon
process
Lateral
epicondyle
Medial
epicondyle
Head
Ulna
Neck
Radius
(d) Posterior view of extended elbow
Figure 7.26c-d

58. Phalanges Distal Middle Proximal Metatarsals Medial cuneiform1 2 3 4 5
Metatarsals
Medial
cuneiform
Intermediate
cuneiform
Lateral
cuneiform
Navicular
Cuboid
Tarsals
Talus
Trochlea
of talus
Calcaneus
(a) Superior view
Figure 7.33a

59. Animation: Rotatable bones of the foot
Talus
Facet for
medial
malleolus
Navicular
Intermediate
cuneiform
Sustentac-
ulum tali
(talar shelf)
First metatarsal
Calcaneus
Medial
cuneiform
Calcaneal
tuberosity
(b) Medial view
PLAY
Animation: Rotatable bones of the foot
Figure 7.33b

60. Radial notch of the ulna Olecranon process Trochlear notch Head
Head of
radius
Neck
Coronoid
process
Radial
tuberosity
Neck of
radius
Proximal
radioulnar
joint
Interosseous
membrane
Ulna
Radius
Ulnar notch
of the radius
Radius
Head of ulna
Styloid
process of ulna
Styloid
process
of radius
Distal radioulnar
joint
Styloid process
of radius
(a) Anterior view
(b) Posterior view
Figure 7.27a-b

61. (c) Proximal portion of ulna, lateral view
Olecranon process
View
Trochlear notch
Coronoid process
Radial notch
(c) Proximal portion of ulna,
lateral view
Ulnar notch of radius
Articulation
for lunate
Articulation
for scaphoid
Styloid
process
Head
of ulna
Styloid
process
View
(d) Distal ends of the radius and
ulna at the wrist
Figure 7.27c-d

62. (a) Anterior view of left hand (b) Posterior view of left hand
Phalanges
• Distal
• Middle
• Proximal
Metacarpals
• Head
• Shaft
Sesamoid
bones
• Base
Carpals
Carpals
Carpals
• Trapezium
• Hamate
• Trapezium
• Trapezoid
• Capitate
• Trapezoid
• Scaphoid
• Pisiform
• Scaphoid
• Triquetrum
Radius
• Lunate
Ulna
Radius
(a) Anterior view of left hand
(b) Posterior view of left hand
Figure 7.28a-b

63. Animation: Rotatable pelvis
Base of sacrum
Iliac crest
Sacroiliac
joint
Iliac fossa
Anterior
superior
iliac spine
Sacral
promontory
Coxal
bone
(os coxae
or hip
bone)
Anterior inferior
iliac spine
llium
Sacrum
Pubic
bone
Pelvic brim
Coccyx
Acetabulum
Pubic tubercle
Ischium
Pubic crest
Pubic symphysis
Pubic arch
PLAY
Animation: Rotatable pelvis
Figure 7.29

64. *Comparison of Male and Female Pelves
Female pelvis
Adapted for childbearing
True pelvis (inferior to pelvic brim) defines birth canal
Cavity of the true pelvis is broad, shallow, and has greater capacity

65. *Comparison of Male and Female Pelves
Male pelvis
Tilted less forward
Adapted for support of male’s heavier build and stronger muscles
Cavity of true pelvis is narrow and deep

66. Comparison of Male and Female Pelves
Characteristic
Female
Male
Bone thickness
Lighter, thinner, and smoother
Heavier, thicker, and more prominent markings
Pubic arch/angle
80˚– 90˚
50˚– 60˚
Acetabula
Small; farther apart
Large; closer together
Sacrum
Wider, shorter; sacral curvature is accentuated
Narrow, longer; sacral promontory more ventral
Coccyx
More movable; straighter
Less movable; curves ventrally

67. Table 7.4

68. Table 7.4

69. Table 7.4

70. Animation: Rotatable pelvis
Base of sacrum
Iliac crest
Sacroiliac
joint
Iliac fossa
Anterior
superior
iliac spine
Sacral
promontory
Coxal
bone
(os coxae
or hip
bone)
Anterior inferior
iliac spine
llium
Sacrum
Pubic
bone
Pelvic brim
Coccyx
Acetabulum
Pubic tubercle
Ischium
Pubic crest
Pubic symphysis
Pubic arch
PLAY
Animation: Rotatable pelvis
Figure 7.29

71. *Hip Bone Three regions Ilium Superior region of the coxal bone
Auricular surface articulates with the sacrum (sacroiliac joint)
Ischium
Posteroinferior part of hip bone
Pubis
Anterior portion of hip bone
Midline pubic symphysis joint

72. (a) Lateral view, right hip bone
Anterior gluteal
line
Ilium
Ala
Posterior
gluteal line
Iliac crest
Posterior
superior
iIiac spine
Anterior
superior
iliac spine
Posterior inferior
iliac spine
Inferior
gluteal line
Greater sciatic
notch
Anterior inferior
iliac spine
Ischial body
Acetabulum
Ischial spine
Lesser sciatic
notch
Pubic body
Pubis
Ischium
Inferior ramus
of pubis
Ischial
tuberosity
Obturator foramen
Ischial ramus
(a) Lateral view, right hip bone
Figure 7.30a

73. (b) Medial view, right hip bone
Ilium
Iliac fossa
Iliac crest
Posterior
superior
iliac spine
Anterior
superior
iliac spine
Posterior
inferior
iliac spine
Anterior inferior
iliac spine
Auricular
surface
Body of
the ilium
Arcuate line
Greater sciatic notch
Superior ramus
of pubis
Ischial spine
Lesser sciatic notch
Pubic tubercle
Obturator
foramen
Articular surface
of pubis (at pubic
symphysis)
Ischium
Inferior ramus
of pubis
Ischial ramus
(b) Medial view, right hip bone
Figure 7.30b

74. *Comparison of Male and Female Pelves
Female pelvis
Adapted for childbearing
True pelvis (inferior to pelvic brim) defines birth canal
Cavity of the true pelvis is broad, shallow, and has greater capacity

75. *Comparison of Male and Female Pelves
Male pelvis
Tilted less forward
Adapted for support of male’s heavier build and stronger muscles
Cavity of true pelvis is narrow and deep

76. Comparison of Male and Female Pelves
Characteristic
Female
Male
Bone thickness
Lighter, thinner, and smoother
Heavier, thicker, and more prominent markings
Pubic arch/angle
80˚– 90˚
50˚– 60˚
Acetabula
Small; farther apart
Large; closer together
Sacrum
Wider, shorter; sacral curvature is accentuated
Narrow, longer; sacral promontory more ventral
Coccyx
More movable; straighter
Less movable; curves ventrally

77. Table 7.4

78. Table 7.4

79. Table 7.4

80. Carries the weight of the body Subjected to exceptional forces
The Lower Limb
Carries the weight of the body
Subjected to exceptional forces
Three segments of the lower limb
Thigh: femur
Leg: tibia and fibula
Foot: 7 tarsal bones in the ankle, 5 metatarsal bones in the metatarsus, and 14 phalanges in the toes

81. Femur
Largest and strongest bone in the body
Articulates proximally with the acetabulum of the hip and distally with the tibia and patella

82. Foot: Metatarsals and Phalanges
Five metatarsal bones (#1 to #5)
Enlarged head of metatarsal 1 forms the “ball of the foot”
Phalanges
The 14 bones of the toes
Each digit (except the hallux) has three phalanges
Hallux has no middle phalanx

83. Phalanges Distal Middle Proximal Metatarsals Medial cuneiform1 2 3 4 5
Metatarsals
Medial
cuneiform
Intermediate
cuneiform
Lateral
cuneiform
Navicular
Cuboid
Tarsals
Talus
Trochlea
of talus
Calcaneus
(a) Superior view
Figure 7.33a

84. Animation: Rotatable bones of the foot
Talus
Facet for
medial
malleolus
Navicular
Intermediate
cuneiform
Sustentac-
ulum tali
(talar shelf)
First metatarsal
Calcaneus
Medial
cuneiform
Calcaneal
tuberosity
(b) Medial view
PLAY
Animation: Rotatable bones of the foot
Figure 7.33b

85. Arches allow the foot to bear weight Three arches
Arches of the Foot
Arches are maintained by interlocking foot bones, ligaments, and tendons
Arches allow the foot to bear weight
Three arches
Lateral longitudinal
Medial longitudinal
Transverse

86. (a) Lateral aspect of right foot
Medial longitudinal
arch
Transverse arch
Lateral
longitudinal arch
(a) Lateral aspect of right foot
Figure 7.34a