1. Bone Tissue

2. Support Provides attachment for tendons of skeletal muscles Provides attachment for tendons of skeletal muscles

3. Protection Protects internal organs Protects internal organs Example: Skull (brain), vertebrae (spinal cord), and rib cage ( heart and lungs)

4. Assistance in movement Contraction of muscles results in pulling of bone due to tendons Contraction of muscles results in pulling of bone due to tendons

5. Mineral Homeostasis Stores calcium and phosphorous Stores calcium and phosphorous

6. Blood Cell Production Red bone marrow produces red blood cells, white blood cells and platelets Red bone marrow produces red blood cells, white blood cells and platelets

7. Triglyceride Storage Yellow bone marrow stores triglycerides Yellow bone marrow stores triglycerides

8. Newborns Have only red bone marrow Have only red bone marrow

9. Newborns Red bone marrow changes into yellow bone marrow with increasing age Red bone marrow changes into yellow bone marrow with increasing age

10. Structure of Bone Diaphysis Diaphysis Epiphysis Epiphysis Metaphyses Metaphyses Articular cartilage Articular cartilage Periosteum Periosteum Medullary cavity Medullary cavity Endosteum Endosteum

11. Diaphysis Bone’s body or shaft Bone’s body or shaft

13. Epiphysis The distal and proximal ends of the bone The distal and proximal ends of the bone

15. Metaphysis The region where the diaphysis joins the epiphysis The region where the diaphysis joins the epiphysis

17. Metaphysis When the bone is growing the metaphysis consists of an epiphyseal plate. This is a layer of hyaline cartilage that allows the bone to grow in length. When the bone is growing the metaphysis consists of an epiphyseal plate. This is a layer of hyaline cartilage that allows the bone to grow in length.

18. Metaphysis When the bone stops growing the cartilage is replaced by bone and becomes the epiphyseal line. When the bone stops growing the cartilage is replaced by bone and becomes the epiphyseal line.

19. Articular Cartilage Hyaline cartilage that covers the epiphyses in order to reduce friction Hyaline cartilage that covers the epiphyses in order to reduce friction

21. Periosteum Dense irregular tissue that surrounds the bone. Dense irregular tissue that surrounds the bone.

23. Periosteum Contains osteoblasts responsible for bone growth in thickness. Contains osteoblasts responsible for bone growth in thickness.

24. Medullary Cavity The space in the diaphysis that contains yellow bone marrow. The space in the diaphysis that contains yellow bone marrow.

26. Endosteum A thin membrane that lines the medullary cavity A thin membrane that lines the medullary cavity

28. Bone Histology 25% water 25% water 25% collagen fibers 25% collagen fibers 50% mineral salts 50% mineral salts

29. Bone Histology Most mineral salts are calcium phosphate and calcium carbonate Most mineral salts are calcium phosphate and calcium carbonate

30. Bone Histology Continued These minerals crystallize only in the presence of collagen fibers These minerals crystallize only in the presence of collagen fibers

31. Bone Histology Continued Crystallized inorganic mineral salts responsible for hardness Crystallized inorganic mineral salts responsible for hardness

32. Bone Cells 1. Osteogenic Cells Only bone cells that undergoes cell division Only bone cells that undergoes cell division Daughter cells becomes osteoblasts Daughter cells becomes osteoblasts

33. Bone Cells Osteoblasts Osteoblasts Secretes collagen fibers and organic compounds for matrix Secretes collagen fibers and organic compounds for matrix When mature they become osteocytes When mature they become osteocytes

34. Bone Cells Osteocytes Osteocytes Mature bone cells Mature bone cells Exchange nutrients and waste with blood Exchange nutrients and waste with blood

35. Bone Cells Osteoclasts Breaks down bone matrix or resorption Breaks down bone matrix or resorption Derived from the fusion of 50 monocytes (wbc) Derived from the fusion of 50 monocytes (wbc)

36. Compact Bone Tissue Forms the external layer of all bones and most of the diaphysis in long bones Forms the external layer of all bones and most of the diaphysis in long bones

37. Compact Bone Tissue Provides protection and support Provides protection and support

38. Compact Bone Tissue Compact bone thickest in areas where stress is applied in few directions Compact bone thickest in areas where stress is applied in few directions

39. Compact Bone Tissue 1. Osteons – units in bone

41. Compact Bone Tissue 2. Volkmann’s canals – Tranverse canals in which blood vessels, lymphatic vessels, and nerves reside

43. Compact Bone Tissue 3. Haversian canals – longitudinal canals

45. Compact Bone Tissue 4. Concentric lamellae – rings of calcified matrix

47. Compact Bone Tissue 5. Lacunae – contain osteocytes

49. Compact Bone Tissue 6. Canaliculi – tiny channels filled with extracellular fluid that contain the fingerlike processes of osteocytes.

51. Canaliculi  Connect lacunae with one another

52. Canaliculi  Connect lacuane with Haversian Canals

53. Canaliculi  Allow osteocytes to communicate with each other via gap junction

54. Canaliculi  Allow exchange of nutrients and wastes with blood

55. Compact Bone Tissue 7. Interstitial lamellae – fragments of older osteons

57. Spongy Bone Tissue Lacks osteons Lacks osteons

58. Spongy Bone Tissue Contains trabeculae which are an irregular latticework of thin columns of bone Contains trabeculae which are an irregular latticework of thin columns of bone

60. Spongy Bone Tissue Contains red bone marrow between spaces of trabeculae Contains red bone marrow between spaces of trabeculae

61. Spongy Bone Tissue Make up most of the bone tissue in short, flat, irregularly shaped bones, and epiphysis of long bones and the narrow rim around the medullary cavity of the diaphysis of long bone Make up most of the bone tissue in short, flat, irregularly shaped bones, and epiphysis of long bones and the narrow rim around the medullary cavity of the diaphysis of long bone

62. Spongy Bone Tissue Red Bone marrow is found in spongy bone tissue of hip bones, ribs, breastbone, back bones, and ends of long bones Red Bone marrow is found in spongy bone tissue of hip bones, ribs, breastbone, back bones, and ends of long bones

63. Spongy Bone Tissue Spongy Bone tissue found where stresses are applied from several directions Spongy Bone tissue found where stresses are applied from several directions

64. Bone Formation 1. Intramembranous ossification 2. Endochondral ossification

65. Intramembranous Ossification Skull bones and mandible form this way Skull bones and mandible form this way Fetal soft spots harden via this process Fetal soft spots harden via this process

66. Intramembranous 1. Development of the center of ossification

68. Development of the center of ossification The site where mesenchymal cells cluster together The site where mesenchymal cells cluster together

69. Development of the center of ossification The mesenchymal cells become osteogenic cells The mesenchymal cells become osteogenic cells

70. Development of the center of ossification These osteogenic cells become osteoblasts These osteogenic cells become osteoblasts

71. Intramembranous 2. Calcification

73. Calcification Secretion of matrix stops Secretion of matrix stops

74. Calcification Osteoblasts now called osteocytes and lie within lacunae Osteoblasts now called osteocytes and lie within lacunae

75. Calcification Calcium and other mineral salt are deposited and the matrix hardens or calcifies Calcium and other mineral salt are deposited and the matrix hardens or calcifies

76. Intramembranous 3. Formation of trabeculae

78. Formation of trabeculae Bone matrix develops into trabeculae to form spongy bone Bone matrix develops into trabeculae to form spongy bone

79. Formation of trabeculae Connective tissue associated with blood vessels in trabeculae become red bone marrow Connective tissue associated with blood vessels in trabeculae become red bone marrow

80. Intramembranous 4. Development of the periosteum

82. Development of the periosteum Mesenchyme condenses around the periphery and becomes the periosteum Mesenchyme condenses around the periphery and becomes the periosteum

83. Development of the periosteum Compact bone replaces spongy bone at the surface Compact bone replaces spongy bone at the surface

84. Development of the periosteum Spongy bone remains in the center Spongy bone remains in the center

85. Endochondral Ossification Replacement of cartilage by bone Replacement of cartilage by bone Most bones are formed this way Most bones are formed this way

86. Endochondral 1. Development of the cartilage model

88. Development of the cartilage model  Mesenchymal cells cluster together in the shape of the future bone and differentiate into chondroblasts

89. Development of the cartilage model  Chondroblasts secrete a cartilage matrix, producing a hyaline cartilage model

90. Development of the cartilage model  A perichondrium develops around the cartilage model

91. Endochondral 2. Growth of the cartilage model

93. Growth of the cartilage model  Once chondroblasts are surrounded by matrix called chondrocytes

94. Growth of the cartilage model  Grows in length because chondrocytes continue to divide and secretion of cartilage matrix

95. Growth of the cartilage model  Grows in width occurs due to addition of more matrix by new chondroblasts that develop from the perichondrium

96. Growth of the cartilage model  Cartilage model calcifies

97. Endochondral 3. Development of the primary ossification center

99. Development of the primary ossification center  A nutrient artery penetrates the perichondrium and calcified cartilage via a nutrient foramen

100. Development of the primary ossification center  Osteogenic cells in perichondrium become osteoblasts

101. Development of the primary ossification center  Osteoblasts secretes a periosteal bone collar made up of compact bone

102. Development of the primary ossification center  Perichondrium becomes periosteum

103. Development of the primary ossification center  Capillaries that penetrate the calcified cartilage induce growth of the primary ossification center

104. Development of the primary ossification center  Osteoblasts deposit bone matrix over calcified cartilage forming spongy bone trabeculae

105. Development of the primary ossification center  As the ossification center grows length wise it begins to destroy the trabeculae which becomes the medullary cavity

106. Endochondral 4. Development of the secondary ossification center

108. Development of the secondary ossification center Epiphyseal artery penetrates epiphyses and a secondary ossification center develops Epiphyseal artery penetrates epiphyses and a secondary ossification center develops

109. Development of the secondary ossification center Bone formation is similar to that of diaphysis except spongy bone trabeculae is not destroyed Bone formation is similar to that of diaphysis except spongy bone trabeculae is not destroyed

110. Endochondral 5. Formation of articular cartilage and the epiphyseal plate

112. Formation of articular cartilage and the epiphyseal plate  Hyaline cartilage that surrounds epiphyses becomes the articular cartilage

113. Formation of articular cartilage and the epiphyseal plate  There is a layer of cartilage between the epiphyses and the diaphysis called the epiphyseal plate

114. Bone Growth  Growth in length  Growth in thickness

115. Growth in Length  Growth in length occurs due to the epiphyseal plate

116. Growth in Length  The epiphyseal plate is made up of a layer of cartilage with four zones

117. Four Zones 1. Zone of resting cartilage  Made up of chondrocytes

119. Zone of resting cartilage  Does not contribute to bone growth

120. Zone of resting cartilage  Anchors epiphyses to the epiphyseal plate

121. Four Zones 2. Zone of proliferating cartilage  Chondrocytes larger

123. Zone of proliferating cartilage  Chondrocytes divide in order to replace dying chondrocytes on the diaphyseal side of the epiphyseal plate

124. Zone of proliferating cartilage  Responsible for lengthening

125. Four Zones 3. Zone of hypertrophic cartilage  Chondrocytes larger

127. Zone of hypertrophic cartilage  Lacunae grows and the matrix between lacunae narrow

128. Zone of hypertrophic cartilage  Responsible for lengthening

129. Four Zones 4. Zone of calcified cartilage  Matrix is calcified

131. Zone of calcified cartilage  Chondrocytes are dead

132. Zone of calcified cartilage  Osteoclasts dissolve the calcified cartilage

133. Zone of calcified cartilage  Osteoblasts from diaphysis invade the area and lay down bone matrix

134. Epiphyseal Line Epiphyseal plate becomes a bony structure called an epiphyseal line between the age of 18 and 25 Epiphyseal plate becomes a bony structure called an epiphyseal line between the age of 18 and 25

135. Epiphyseal Line Bone replaces all the cartilage and the bone can no longer grow in length Bone replaces all the cartilage and the bone can no longer grow in length

136. Growth in Thickness Bone can only grow in thickness by appositional growth Bone can only grow in thickness by appositional growth

137. Growth in Thickness/Step 1 Osteoblasts secrete collagen fibers and organic molecues Osteoblasts secrete collagen fibers and organic molecues

139. Growth in Thickness/Step 1 Bone ridges form on either side of a periosteal blood vessel Bone ridges form on either side of a periosteal blood vessel

141. Growth in Thickness/Step 1 A groove forms for the blood vessel A groove forms for the blood vessel

143. Growth in Thickness/Step 2 The ridges fold and fuse enclosing the blood vessel The ridges fold and fuse enclosing the blood vessel

145. Growth in Thickness/Step 2 The periosteum is now becomes the endosteum surrounding the blood vessel The periosteum is now becomes the endosteum surrounding the blood vessel

146. Growth in Thickness/Step 3 Osteoblasts in the endosteum lay down bone matrix forming new concenteric lamellae Osteoblasts in the endosteum lay down bone matrix forming new concenteric lamellae

148. Growth in Thickness/Step 3 The concenteric lamellae is added toward the center of tunnel The concenteric lamellae is added toward the center of tunnel

149. Growth in Thickness/Step 4 The periosteum lays down new outer concenteric lamellae The periosteum lays down new outer concenteric lamellae Step 1-4 repeats Step 1-4 repeats

151. Calcium Homeostasis When blood calcium levels are below normal, parathyroid hormone is released by the parathyroid glands. When blood calcium levels are below normal, parathyroid hormone is released by the parathyroid glands.

152. Calcium Homeostasis Parathyroid hormone increases bone resorption. In other words it increases the activity of osteoclasts, thereby breaking down bone and releasing more calcium into the blood stream. Parathyroid hormone increases bone resorption. In other words it increases the activity of osteoclasts, thereby breaking down bone and releasing more calcium into the blood stream.

153. Calcium Homeostasis Parathyroid hormone also act on the kidneys to decrease loss of calcium in urine Parathyroid hormone also act on the kidneys to decrease loss of calcium in urine

154. Calcium Homeostasis When blood calcium levels are high, calcitonin is released by the thyroid gland in order to increase calcium uptake and stimulate bone formation. When blood calcium levels are high, calcitonin is released by the thyroid gland in order to increase calcium uptake and stimulate bone formation.