1. The Skeletal System

2. The Skeletal System Parts of the skeletal system Bones (skeleton)
Joints
Cartilages
Ligaments
Two subdivisions of the skeleton
Axial skeleton
Appendicular skeleton

3. Functions of Bones Support the body Protect soft organs
Allow movement due to attached skeletal muscles
Store minerals and fats
Blood cell formation

4. Bones of the Human Body The adult skeleton has 206 bones
Two basic types of bone tissue
Compact bone
Dense, smooth
Homogeneous
Spongy bone
Small needle-like pieces of bone
Many open spaces
Figure 5.2b

5. Classification of Bones on the Basis of Shape
Figure 5.1

6. Classification of Bones
Long bones
Typically longer than they are wide
Have a shaft with heads at both ends
Contain mostly compact bone
Example:
Femur
Humerus

7. Classification of Bones
Figure 5.1a

8. Classification of Bones
Short bones
Generally cube-shape
Contain mostly spongy bone
Sesamoid bone—special type that forms within tendons (Ex: patella)
Example:
Carpals
Tarsals

9. Classification of Bones
Figure 5.1b

10. Classification of Bones
Flat bones
Thin, flattened, and usually curved
Two thin layers of compact bone surround a layer of spongy bone
Example:
Skull
Ribs
Sternum

11. Classification of Bones
Figure 5.1c

12. Classification of Bones
Irregular bones
Irregular shape
Do not fit into other bone classification categories
Example:
Vertebrae
Hip bones

13. Classification of Bones
Figure 5.1d

14. Anatomy of a Long Bone Diaphysis Shaft
Makes up most of the bone’s length
Composed of compact bone
Epiphysis
Ends of the bone
Composed of a thin layer of compact bone enclosing spongy bone

15. Anatomy of a Long Bone
Figure 5.2a

16. Anatomy of a Long Bone Periosteum Outside covering of the diaphysis
Fibrous connective tissue membrane
Sharpey’s fibers (Perforating fibers)
Connective tissue fibers that secure periosteum to underlying bone
Arteries
Supply bone cells with nutrients

17. Anatomy of a Long Bone
Figure 5.2c

18. Anatomy of a Long Bone Articular cartilage
Covers the external surface of the epiphyses
Made of hyaline cartilage
Decreases friction at joint surfaces

19. Anatomy of a Long Bone Epiphyseal plate
Flat plate of hyaline cartilage seen in young, growing bone
Epiphyseal line
Remnant of the epiphyseal plate—flat plate of hyaline cartilage that causes lengthwise growth of a long bone.
Seen in adult bones

20. Anatomy of a Long Bone
Figure 5.2a

21. Anatomy of a Long Bone Medullary cavity Cavity inside of the shaft
Contains yellow marrow (mostly fat) in adults
Contains red marrow (for blood cell formation) in infants

22. Anatomy of a Long Bone
Figure 5.2a

23. Bone Markings Surface features of bones (bone markings)
Sites of attachments for muscles, tendons, and ligaments
Passages for nerves and blood vessels
Categories of bone markings
Projections or processes—grow out from the bone surface
Depressions or cavities—indentations

24. Bone Markings
Table 5.1 (1 of 2)

25. Bone Markings
Table 5.1 (2 of 2)

26. Formation of the Human Skeleton
In embryos, the skeleton is primarily hyaline cartilage
During development, much of this cartilage is replaced by bone
Cartilage remains in isolated areas
Bridge of the nose
Parts of ribs
Joints

27. Bone Growth (Ossification)
Epiphyseal plates allow for lengthwise growth of long bones during childhood
New cartilage is continuously formed
Older cartilage becomes ossified
Cartilage is broken down
Enclosed cartilage is digested away, opening up a medullary cavity
Bone replaces cartilage through the action of osteoblasts

28. Bone Growth (Ossification)
Bones are remodeled and lengthened until growth stops
Bones are remodeled in response to two factors
Blood calcium levels
Pull of gravity and muscles on the skeleton
Bones grow in width (called appositional growth)
Long bone growth is controlled by growth hormones and sex hormones (puberty)

29. Long Bone Formation and Growth
Bone starting to replace cartilage
Epiphyseal plate cartilage
Articular cartilage
Spongy bone
In a child
In a fetus
In an embryo
New bone forming
Growth in bone width
Growth in bone length
Blood vessels
Hyaline cartilage
New center of bone growth
Medullary cavity
Bone collar
Hyaline cartilage model
(a)
Figure 5.4a

30. Long Bone Formation and Growth
Figure 5.4b

31. Types of Bone Cells Osteocytes—mature bone cells
Osteoblasts—bone-forming cells
Osteoclasts—bone-destroying cells
Break down bone matrix for remodeling and release of calcium in response to parathyroid hormone (PTH)
Bone remodeling is performed by both osteoblasts and osteoclasts

32. Bone Fractures Fracture—break in a bone Types of bone fractures
Closed (simple) fracture—break that does not penetrate the skin
Open (compound) fracture—broken bone penetrates through the skin
Bone fractures are treated by reduction (realignment of bone ends) and immobilization

33. Common Types of Fractures
Table 5.2

34. Repair of Bone Fractures
Hematoma (blood-filled swelling) is formed
New capillaries begin to grow at the site of damage and break is splinted by fibrocartilage to form a callus
Fibrocartilage callus is replaced by a bony callus (spongy bone)
Bony callus is remodeled to form a permanent patch

35. Stages in the Healing of a Bone Fracture
Hematoma
External callus
Bony callus of spongy bone
Healed fracture
New blood vessels
Internal callus (fibrous tissue and cartilage)
Spongy bone trabecula
Hematoma formation
Fibrocartilage callus formation
Bony callus formation
Bone remodeling
Figure 5.5

36. The Axial Skeleton Forms the longitudinal axis of the body
Divided into three parts
Skull
Vertebral column
Bony thorax

37. The Axial Skeleton
Figure 5.6a

38. The Axial Skeleton
Figure 5.6b

39. The Skull Two sets of bones Cranium Facial bones
Bones are joined by sutures
Only the mandible is attached by a freely movable joint

40. Human Skull, Lateral View
Figure 5.7

41. Human Skull, Superior View
one of the paired openings in the sphenoid bone that transmits an optic nerve and its associated ophthalmic artery.
(Pituitary gland)
(Cranial nerve V passes to chewing muscles of lower jaw)
Figure 5.8

42. Human Skull, Inferior View
Figure 5.9

43. Human Skull, Anterior View
(cranial nerves III, IV, VI control eye movements)
(tear ducts)
(bony nasal septum)
Figure 5.11

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

45. Paranasal Sinuses
Figure 5.10a

46. Paranasal Sinuses
Figure 5.10b

47. 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

48. The Hyoid Bone
Figure 5.12

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

50. The Fetal Skull
Figure 5.13a

51. The Fetal Skull
Figure 5.13b

52. 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

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

54. The Vertebral Column
Figure 5.14

55. The Vertebral Column The spine has a normal curvature
Primary curvatures are the spinal curvatures of the thoracic and sacral regions
Present from birth
Produce the C-shaped spin of a newborn
Secondary curvatures are the spinal curvatures of the cervical and lumbar regions
Develop after birth
Allow adults to center body weight on our lower limbs.

56. The Vertebral Column
Figure 5.15

57. The Vertebral Column
Figure 5.16

58. A Typical Vertebrae, Superior View
Allows vertebrae to form joints with adjacent vertebrae.
Figure 5.17

59. Sacrum and Coccyx Sacrum
Formed by the fusion of five vertebrae; forms the posterior wall of the pelvis
Alae—articulate laterally with the hip bones, forming the sacroiliac joints
Midline is roughened by the median sacral crest—the fused processes of the sacral vertebrae
Vertebral canal continues as the sacral canal and terminates in an opening called the sacral hiatus

60. Sacrum and Coccyx Coccyx
Formed from the fusion of three to five vertebrae
“Tailbone,” or remnant of a tail that other vertebrates have

61. Sacrum and Coccyx
Figure 5.19

62. The Bony Thorax Forms a cage to protect major organs
Consists of three parts
Sternum
Ribs
True ribs (pairs 1–7)
False ribs (pairs 8–12)
Floating ribs (pairs 11–12)
Thoracic vertebrae

63. The Bony Thorax Men do not have one rib fewer than women!!!
Figure 5.20a

64. The Appendicular Skeleton
Composed of 126 bones
Limbs (appendages)
Pectoral girdle
Pelvic girdle

65. The Appendicular Skeleton
Figure 5.6a

66. The Appendicular Skeleton
Figure 5.6b

67. The Pectoral (Shoulder) Girdle
Composed of two bones
Clavicle—collarbone
Scapula—shoulder blade
These bones allow the upper limb to have exceptionally free movement
The clavicle acts as a brace to hold the arm away from the top of the thorax and helps prevent shoulder dislocation.

68. Bones of the Shoulder Girdle
Figure 5.21a

69. Bones of the Shoulder Girdle
(Nerve passageway)
Anchors muscles of the arm
(Receives the head of the arm bone)
Figure 5.21c–d