1. Bone & Skeletal Tissue
Chapter 6

2. Functions of the Skeletal system
Support
Protection
Movement
Mineral storage
Hematopoiesis (blood cell formation)

3. Skeletal Cartilages

4. Cartilages of the respiratory tract

5. Classification of Bones
Bone are identified by:
shape
internal tissues
bone markings

6. Bone Shapes Long bones Flat bones Sutural bones Irregular bones
Short bones
Sesamoid bones

7. Long Bones
Figure 6–1a

8. Long Bones Are long and thin
Are found in arms, legs, hands, feet, fingers, and toes

9. Flat Bones
Figure 6–1b

10. Flat Bones Are thin with parallel surfaces
Are found in the skull, sternum, ribs, and scapula

11. Sutural Bones
Figure 6–1c

12. Sutural Bones Are small, irregular bones
Are found between the flat bones of the skull

13. Irregular Bones
Figure 6–1d

14. Irregular Bones Have complex shapes Examples: spinal vertebrae
pelvic bones

15. Short Bones
Figure 6–1e

16. Short Bones
Are small and thick
Examples:
ankle
wrist bones

17. Sesamoid Bones
Figure 6–1f

18. Sesamoid Bones Are small and flat
Develop inside tendons near joints of knees, hands, and feet

19. Bone Markings Depressions or grooves: Projections: Tunnels:
along bone surface
Projections:
where tendons and ligaments attach
at articulations with other bones
Tunnels:
where blood and nerves enter bone

20. Bone Markings

21. Bone Markings
Table 6–1 (2 of 2)

22. The femur
Long Bones
Figure 6–2a

23. Structure of a long bone
The Humerus

24. Long Bones Diaphysis: Epiphysis: Metaphysis: the shaft
wide part at each end
articulation with other bones
Metaphysis:
where diaphysis and epiphysis meet

25. Flat Bones
The parietal bone of the skull
Figure 6–2b

26. Compact Bone Structure

27. Spongy Bone
Figure 6–6

28. Spongy Bone Structure

29. Bone Cells Make up only 2% of bone mass: osteocytes osteoblasts
osteoprogenitor cells
osteoclasts

30. Bone Cells: Osteoblasts, Osteocytes & Osteoclasts

31. Periosteum
Figure 6–8a

32. Endosteum
Figure 6–8b

33. Bone Development Human bones grow until about age 25 Osteogenesis:
bone formation
Ossification:
the process of replacing other tissues with bone

34. Intramembranous Ossification
Also called dermal ossification:
because it occurs in the dermis
produces dermal bones such as mandible and clavicle
There are 3 main steps in intramembranous ossification

35. Intramembranous Ossification: Step 1
Figure 6–11 (Step 1)

36. Intramembranous Ossification: Step 1
Mesenchymal cells aggregate:
differentiate into osteoblasts
begin ossification at the ossification center
develop projections called spicules

37. Step 2

38. Intramembranous Ossification: Step 2
Blood vessels grow into the area:
to supply the osteoblasts
Spicules connect:
trapping blood vessels inside bone

39. Step 3
Figure 6–11 (Step 3)

40. Intramembranous Ossification: Step 3
Spongy bone develops and is remodeled into:
osteons of compact bone
periosteum
or marrow cavities

41. Endochondral Ossification
Ossifies bones that originate as hyaline cartilage
Most bones originate as hyaline cartilage

42. Endochondral Ossification: Step 1
Chondrocytes in the center of hyaline cartilage:
enlarge
form struts and calcify
die, leaving cavities in cartilage
Figure 6–9 (Step 1)

43. Step 2

44. Endochondral Ossification: Step 2
Blood vessels grow around the edges of the cartilage
Cells in the perichondrium change to osteoblasts:
producing a layer of superficial bone around the shaft which will continue to grow and become compact bone (appositional growth)

45. Step 3 Blood vessels enter the cartilage:
bringing fibroblasts that become osteoblasts
spongy bone develops at the primary ossification center

46. Step 4 Remodeling creates a marrow cavity:
bone replaces cartilage at the metaphyses

47. Step 5 Capillaries and osteoblasts enter the epiphyses:
creating secondary ossification centers

48. Step 6

49. Endochondral Ossification: Step 6
Epiphyses fill with spongy bone:
cartilage within the joint cavity is articulation cartilage
cartilage at the metaphysis is epiphyseal cartilage

50. Endochondral Ossification
Appositional growth:
compact bone thickens and strengthens long bone with layers of circumferential lamellae
PLAY
Endochondral Ossification
Figure 6–9 (Step 2)

51. Appostional Growth

52. Blood Supply of Mature Bones
3 major sets of blood vessels develop
Figure 6–12

53. Blood Vessels of Mature Bones
Nutrient artery and vein:
a single pair of large blood vessels
enter the diaphysis through the nutrient foramen
femur has more than 1 pair
Metaphyseal vessels:
supply the epiphyseal cartilage
where bone growth occurs

54. Blood Vessels of Mature Bones
Periosteal vessels provide:
blood to superficial osteons
secondary ossification centers

55. Mature Bones As long bone matures: osteoclasts enlarge marrow cavity
osteons form around blood vessels in compact bone

56. Effects of Exercise on Bone
Mineral recycling allows bones to adapt to stress
Heavily stressed bones become thicker and stronger

57. Bone Degeneration Bone degenerates quickly
Up to 1/3 of bone mass can be lost in a few weeks of inactivity

58. Wolff’s Law
Tension and compression cycles create a small electrical potential that stimulates bone deposition and increased density at points of stress.

59. Effects of Hormones and Nutrition on Bone
Normal bone growth and maintenance requires nutritional and hormonal factors

60. Minerals A dietary source of calcium and phosphate salts:
plus small amounts of magnesium, fluoride, iron, and manganese

61. Calcitriol The hormone calcitriol: is made in the kidneys
helps absorb calcium and phosphorus from digestive tract
synthesis requires vitamin D3 (cholecalciferol)

62. Vitamins
Vitamin C is required for collagen synthesis, and stimulates osteoblast differentiation
Vitamin A stimulates osteoblast activity
Vitamins K and B12 help synthesize bone proteins

63. Other Hormones Growth hormone and thyroxine stimulate bone growth
Estrogens and androgens stimulate osteoblasts
Calcitonin and parathyroid hormone regulate calcium and phosphate levels

64. Hormones for Bone Growth and Maintenance

65. Chemical Composition of Bone
Figure 6–13

66. Bone homeostasis

67. Calcitonin and Parathyroid Hormone Control
Bones:
where calcium is stored
Digestive tract:
where calcium is absorbed
Kidneys:
where calcium is excreted

68. Parathyroid Hormone (PTH)
Produced by parathyroid glands in neck
Increases calcium ion levels by:
stimulating osteoclasts
increasing intestinal absorption of calcium
decreases calcium excretion at kidneys

69. Parathyroid Hormone (PTH)
Figure 6–14a

70. Calcitonin
Figure 6–14b

71. Calcitonin Secreted by C cells (parafollicular cells) in thyroid
Decreases calcium ion levels by:
inhibiting osteoclast activity
increasing calcium excretion at kidneys

72. A misleading view of bone homeostasis
Calcitonin does not play a central role in maintaining blood plasma Ca++ levels in adults.
It is important to maintaining bone density, though.

73. Fracture Repair: Step 1
Figure 6–15 (Step 1)

74. Fracture Repair: Step 1 Bleeding: Bone cells in the area die
produces a clot (fracture hematoma)
establishes a fibrous network
Bone cells in the area die

75. Fracture Repair: Step 2
Figure 6–15 (Step 2)

76. Fracture Repair: Step 2 Cells of the endosteum and periosteum:
Divide and migrate into fracture zone
Calluses stabilize the break:
external callus of cartilage and bone surrounds break
internal callus develops in marrow cavity

77. Fracture Repair: Step 3
Figure 6–15 (Step 3)

78. Fracture Repair: Step 3 Osteoblasts:
replace central cartilage of external callus
with spongy bone

79. Fracture Repair: Step 4
Figure 6–15 (Step 4)

80. Fracture Repair: Step 4
Osteoblasts and osteocytes remodel the fracture for up to a year:
reducing bone calluses

81. Common fracture types

82. The Major Types of Fractures
Pott’s fracture
Figure 6–16 (1 of 9)

83. Comminuted fractures

84. Transverse fractures
Figure 6–16 (3 of 9)

85. Spiral fractures
Figure 6–16 (4 of 9)

86. Displaced fractures
Figure 6–16 (5 of 9)

87. Colles’ fracture
Figure 6–16 (6 of 9)

88. Greenstick fracture
Figure 6–16 (7 of 9)

89. Epiphyseal fractures

90. Compression fractures
Figure 6–16 (9 of 9)

91. Depression fracture of the skull

92. Age and Bones Bones become thinner and weaker with age
Osteopenia begins between ages 30 and 40
Women lose 8% of bone mass per decade, men 3%

93. Effects of Bone Loss
The epiphyses, vertebrae, and jaws are most affected:
resulting in fragile limbs
reduction in height
tooth loss

94. Osteoporosis Severe bone loss Affects normal function
Over age 45, occurs in:
29% of women
18% of men

95. Hormones and Bone Loss Estrogens and androgens help maintain bone mass
Bone loss in women accelerates after menopause

96. Cancer and Bone Loss
Cancerous tissues release osteoclast-activating factor:
that stimulates osteoclasts
and produces severe osteoporosis

97. Some decorative arrangements

98. I dare not Jim!