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42 Cards in this Set
- Front
- Back
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What is bone?
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- Specialized CT with a mineralized extracellular matrix.
- Main component of adult skeletal system - Mobilizable store for ions (calcium & phosphate) |
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What is bone made up of?
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Bone organs are made up of bone tissue, other CT, fat, cartilage, bone marrow, blood vessels, and nerves
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What are the components of bone?
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Organic Components
Hydroxyapatite crystals [Ca10(PO4)6(OH)2] |
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What are the Organic components of bone made of?
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- Cells (osteoblasts, osteocytes, etc.)
- Extracellular matrix -->Type I collagen (90%) -->Ground substance (10%) |
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Where are the Hydroxyapatite crystals found?
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- (75% weight, 45% volume).
- Located within collagen fibrils and components of the ground substance. |
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What are the two appearances of bone?
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Spongy (trabecular, cancellous)
Compact (dense, cortical) |
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What are the characteristics of Spongy Bone?
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Sponge-like meshwork consisting of trabeculae
Anastomosing spicules of bone tissue Open spaces occupied by bone marrow and blood vessels |
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What are the characteristics Compact Bone?
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Dense layer forming outside of bone
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What defines Immature bone?
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Bone initially formed in development.
More cells randomly oriented, interlacing arrangement of fibers |
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What is another name for Immature Bone?
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(primary, woven)
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What constitutes Mature bone?
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- Cylindrical units: osteons.
- Structurally superior. - Replaces woven bone. |
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What is another name for Mature bone?
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(secondary, lamellar)
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What is Compact bone and spongy bone composed of in an Adult?
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Lamellar bone
- Osteon - Interstitial lamellae. - Inner and Outer circumferential lamellae. |
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What runs parallel within the lamellae?
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Collagen Fibers
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What comprises the Osteon?
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(Haversion system)
Concentric lamellae Lacunae |
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_____ moves from the marrow cavity though the bone to the periosteum.
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Blood
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What are the remnants of the concentric lamellae?
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Interstitial Lamellae
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What connect blood vessels of adjacent Haversian canal?
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Volkmann’s canals
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What are the cells of bone tissue?
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Osteoblasts
Osteocytes Osteoprogenitor cells Bone Lining cells Osteoclasts |
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What do Osteoblasts do?
Where do they come from? Where are they located? What is their shape? What type is the cytoplasm/ |
- Bone forming cells
- Derived from osteoprogenitor cells. - Located on surface of bone. -Cuboidal or polygonal in shape. Basophilic cytoplasm. Synthesize osteoid. (unmineralized bone matrix) Mineralize osteoid. |
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Where are Osteocytes?
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In lacunae
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What are Osteoprogenitor cells?
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Stem cells of periosteum and marrow cavity
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What are bone lining cells?
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Quiescent osteoblasts of the endosteum and periosteum.
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Osteoblasts become _____ in matrix and become ______.
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entrapped, osteocytes
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What are Matrix vesicles in bone filled with?
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Calcium
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What is on the osteoblast cell surface resulting in crystalization of CaPO4
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Alkaline phosphatase
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What characterizes Osteocytes?
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- Completely surrounded by bone tissue.
- Cell processes in canaliculi contact each other by gap junctions. - Have some limited capability to produce and resorb bone. - Derived from osteoblasts. |
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Osteocytes are entrapped in what?
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lacunae
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What are the characteristics of Osteoprogenitor cells?
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- Derived from mesenchymal stem cells.
- Can divide and become osteoblasts. - Located in cellular layer of periosteum (and early endosteum - not adult) |
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What are the characteristics of Bone lining cells?
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- Simple squamous cells on all bone surfaces.
- Quiescent osteoblasts. - Connected via gap junctions. - Periosteal and Endosteal cells. |
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What are Osteoclasts?
What are they Derived from? What is their function? |
Large multinucleated cells.
Derived from fusion of monocytes). Function is bone resorption |
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How does an osteoclast go about with bone resorption?
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- Form Howship’s lacunae (subosteoclastic compartment).
- “Ruffled border” adjacent to bone (and “sealing zone”). - Acidify (via proton pumps) and release hydrolytic enzymes (exocytosis of vesicles) onto bone surface |
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What are the characteristics of embryonic Intramembranous ossification?
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Bone formed directly by condensation of mesenchymal cells.
Flat bones of skull and face, mandible, clavicle. |
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What are the characteristics of Endochondral ossification
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- Bone formed in relation to a previously formed cartilage model.
- Bones of extremities, axial skeleton |
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What are the steps of Endochondral ossification?
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(1)Formation of cartilage model.
(2)Formation of periosteal bone collar. (3)Hypertrophy of chondrocytes. - Production of Type II collagen (4)Cartilage matrix calcification. - Chondrocytes degenerate. (5)Invasion of blood vessels. - Osteoprogenitor and hemopoietic cells (6)Production of bone matrix on calcified cartilage. |
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How is the Epiphyseal plate formed?
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Formed by creation of 1° & 2 ° centers of ossification
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What are the various zones of the Epiphyseal plate from closest to the Diaphysis out?
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Ossification Zone (Vascular Invasion)
Hypertrophy and calcification zone Proliferative zone Reserve (resting) zone |
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_____ of the bone occurs when new cartilage matrix is produced at the _____.
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Lengthening, epiphyseal plate
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What happens to cause lengthening of the bone?
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- Matrix produced in zone of proliferation
- Pushes the epiphysis away from the diaphysis, thus causing elongation of the bone |
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What happens during Bone Growth?
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Thickness of epiphyseal plate remains constant.
- Amount of new cartilage produced equals the amount resorbed. - Resorbed cartilage is replaced by trabecular (spongy) bone (woven bone first, later by lamellar bone) |
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What has to happen to bone as it elongates?
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Remodeling is required:
- Preferential resorption of bone in some areas. - Deposition of bone in other areas. - Increase in bone width is by appositional growth at the periosteum. |
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What forms resorption canals to form new osteons?
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Osteoclasts
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