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

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

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

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

5. 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

6. Classification of Bones
Figure 5.1a

7. Classification of Bones
Short bones
Generally cube-shape
Contain mostly spongy bone
Example:
Carpals
Tarsals

8. Classification of Bones
Figure 5.1b

9. 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

10. Classification of Bones
Figure 5.1c

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

12. Classification of Bones
Figure 5.1d

13. Anatomy of a Long Bone Diaphysis Shaft Composed of compact bone
Epiphysis
Ends of the bone
Composed mostly of spongy bone
Start Here

14. Anatomy of a Long Bone
Figure 5.2a

15. Anatomy of a Long Bone Periosteum Outside covering of the diaphysis
Fibrous connective tissue membrane
Sharpey’s fibers
Secure periosteum to underlying bone
Arteries
Supply bone cells with nutrients

16. Anatomy of a Long Bone
Figure 5.2c

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

18. Anatomy of a Long Bone
Figure 5.2a

19. 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

20. Anatomy of a Long Bone
Figure 5.2a

21. Bone Markings Surface features of bones
Sites of attachments for muscles, tendons, and ligaments
Passages for nerves and blood vessels

22. Microscopic Anatomy of Bone
Osteon (Haversian system)
A unit of bone containing central canal and matrix rings
Central (Haversian) canal
Opening in the center of an osteon
Carries blood vessels and nerves
Perforating (Volkman’s) canal
Canal perpendicular to the central canal

23. Microscopic Anatomy of Bone
Figure 5.3a

24. Microscopic Anatomy of Bone
Lacunae
Cavities containing bone cells (osteocytes)
Arranged in concentric rings
Lamellae
Rings around the central canal
Sites of lacunae

25. Microscopic Anatomy of Bone
Figure 5.3b–c

26. Microscopic Anatomy of Bone
Canaliculi
Tiny canals
Radiate from the central canal to lacunae
Form a transport system connecting all bone cells to a nutrient supply

27. Microscopic Anatomy of Bone
Figure 5.3b

28. 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
Bone remodeling is performed by both osteoblasts and osteoclasts

29. Bone cells that aid in remodeling
Osteoblast
Builds new bone
Mature bone cell
Osteocyte
OsteoblastsOsteoblasts are responsible for building new bone and lie at the centre of bone physiology. Their functions include the synthesis of collagen and the control of mineralisation.
OsteoclastsOsteoclasts are specialised cells that resorb bone. They work by sealing off an area of bone surface then, when activated, they pump out hydrogen ions to produce a very acid environment, which dissolves the hydroxyapatite.
OsteocytesBone adapts to applied forces by growing stronger in order to withstand them; it is known that exercise can help to improve bone strength. Osteocytes are thought to be part of the cellular feed-back mechanism which directs bone to form in the places where it is most needed. They lie within mineralised bone and it is thought that they may detect mechanical deformation and mediate the response of the osteoblasts.
Osteoclast
Eats bone

30. 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 and immobilization

31. Common Types of Fractures
Table 5.2

32. Repair of Bone Fractures
Hematoma (blood-filled swelling) is formed
Break is splinted by fibrocartilage to form a callus
Fibrocartilage callus is replaced by a bony callus
Bony callus is remodeled to form a permanent patch

33. 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

34. Stages in the Healing of a Bone Fracture
Hematoma
Hematoma formation
Figure 5.5, step 1

35. Stages in the Healing of a Bone Fracture
Hematoma
External callus
New blood vessels
Internal callus (fibrous tissue and cartilage)
Spongy bone trabecula
Hematoma formation
Fibrocartilage callus formation
Figure 5.5, step 2

36. Stages in the Healing of a Bone Fracture
Hematoma
External callus
Bony callus of spongy bone
New blood vessels
Internal callus (fibrous tissue and cartilage)
Spongy bone trabecula
Hematoma formation
Fibrocartilage callus formation
Bony callus formation
Figure 5.5, step 3

37. 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, step 4

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

39. The Axial Skeleton
Figure 5.6a

40. The Axial Skeleton
Figure 5.6b

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

42. Human Skull, Lateral View
Figure 5.7

43. Human Skull, Superior View
Figure 5.8

44. Human Skull, Inferior View
Figure 5.9

45. Human Skull, Anterior View
Figure 5.11

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

47. Paranasal Sinuses
Figure 5.10a

48. Paranasal Sinuses
Figure 5.10b

49. 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

50. The Hyoid Bone
Figure 5.12

51. Inflammatory Conditions Associated with Joints
Tendonitis—inflammation of tendon sheaths
Arthritis—inflammatory or degenerative diseases of joints
Over 100 different types
The most widespread crippling disease in the United States

52. Clinical Forms of Arthritis
Osteoarthritis
Most common chronic arthritis
Probably related to normal aging processes

53. Clinical Forms of Arthritis
Rheumatoid arthritis
An autoimmune disease—the immune system attacks the joints
Symptoms begin with bilateral inflammation of certain joints
Often leads to deformities

54. Clinical Forms of Arthritis
Gouty arthritis
Inflammation of joints is caused by a deposition of uric acid crystals from the blood
Can usually be controlled with diet

55. Osteoporosis
a medical condition in which the bones become brittle and fragile from loss of tissue, typically as a result of hormonal changes, or deficiency of calcium or vitamin D.

56. Formation of the Human Skeleton
In embryos, the skeleton is primarily hyaline cartilage
During development, much of this cartilage is replaced by bone

57. Developmental Aspects of the Skeletal System
At birth, the skull bones are incomplete
Bones are joined by fibrous membranes called fontanels
Fontanels are completely replaced with bone within two years after birth

58. Ossification Centers in a 12-week-old Fetus
Figure 5.32

59. Skeletal Changes Throughout Life
Fetus
Long bones are formed of hyaline cartilage
Flat bones begin as fibrous membranes
Flat and long bone models are converted to bone
Birth
Fontanels remain until around age 2

60. Skeletal Changes Throughout Life
Adolescence
Epiphyseal plates become ossified and long bone growth ends
Size of cranium in relationship to body
2 years old—skull is larger in proportion to the body compared to that of an adult
8 or 9 years old—skull is near adult size and proportion
Between ages 6 and 11, the face grows out from the skull

61. Skeletal Changes Throughout Life
Figure 5.33a