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33 Cards in this Set
- Front
- Back
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Bone: General Characteristics
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Highly vascular since nutrients can't reach cell by diffusion
No nerve supply, (high nerve supply to periosteum and vasomotor nerves accompany blood vessels) Metabolically active, undergoes continuous remodeling |
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Surface Covering: Periosteum - Structure
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Dense Irregular CT surrounds outer surfaces of bones (except for articular surfaces)
Outer 'fibrous' layer - fibroblasts Inner 'osteogenic' layer - osteoprogenitor cells Sharpey's Fibers (collagen) extend from periosteum into bone |
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Surface Covering: Periosteum - Contents
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Blood vessels, Lymph vessels, Nerves
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Surface Covering: Periosteum - Function
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Protects bone
Essential for growth and maintenance of bone |
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Surface Covering: Endosteum - Structure
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Single layer of osteoprogenitor cells that lines all internal cavities of bone
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Surface Covering: Endosteum - Function
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Growth and Maintenance of bone
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Surface Covering: Articular Cartilage
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Layer of hyaline cartilage w/o perichondrium
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Compact Bone - Appearance, Location
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Appears as a solid mass
Location: peripherally |
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Cancellous (spongy, trabecular) Bone - Appearance, Location
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Appears as a labyrinth of bony spicules and intervening spaces
Location: central |
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Long Bones: Diaphysis
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Shaft
Composition: compact bone w/inner surface lined w/small amount of cancellous bone Surrounds Yellow Marrow Cavity |
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Long Bones: Epiphysis
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Bulbous region at end of diaphysis
Composition: cancellous bone covered w/thin rim of compact bone Surrounds Red Marrow |
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Long Bones: Epiphyseal Plate
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Separates diaphysis and epiphysis
Region from which bone growth and length occurs Composition: During growth - Hyaline Cartilage. After growth - Diaphysis/Epiphysis fuse -> epiphyseal line |
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Flat Bones: Plates (Tables)
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Two plates, inner and outer
Composition: Compact bone |
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Flat Bone: Diploe
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Located between inner and outer plates
Composition: Cancellous bone, line with Red Marrow |
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Red Marrow: Found in, Contains
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Fetus: all bones
Adults: Cranial bones, vertebrae, ribs, irregular bones of hands and feet, epiphysis of long bones Contains myeloid tissue (blood producing) |
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Yellow Marrow: Found in, Contains
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Diaphysis of long bones
Contains mainly adipose tissue, retains potential to convert to red marrow if necessary (major injury) |
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Osteoblasts (Origin, inactive, active, location, secrete, become)
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Originate: Mesenchymal cells (osteoprogenitor cells)
Inactive: flattened and ovoid Active: Cuboidal Located: surfaces of bone tissue (single layer, side by side) Secrete: intercellular matrix (osteoid). Mineralize the osteoid. Surround themselves with intercellular matrix and become osteocytes |
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Osteocytes (Origin, appearance, function)
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Origin: Osteoblasts surrounded by minteralized intercellular matrix, lie 'real' cavities (lacunae)
Appear: Long cytoplasmic processes extend from cell body through tiny canals called 'canaliculi' to contact other cells via gap junctions Appear similar to osteoblasts Function: Transport materials btw blood and bone and maintain intercellular matrix |
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Osteoclasts (Origin, appearance, location, function)
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Originate: monocytes in bone marrow
Appear: large, branched, motile cells w/5-50 nuclei Located: surfaces of bone tissue in depressions called Howship's lacunae Function: Resorm bone via proteolytic enzymes (respond to hormonal signals) |
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Extracellular Matrix: Organic Portion (Osteoid) - Fiber Component
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90% of osteoid
Collagen type I fibers |
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Extracellular Matrix: Organic Portion (Osteoid) - Ground Substance
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Proteoglycans (chondroitin and keratan sulfates)
Non-Sulfated Glycosaminoglycans (hyaluronic acid) Glycoproteins (Bind Ca++) |
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Extracellular Matrix - Inorganic Portion
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Primarily calcium and phosphorus
Form hydroxyapatite crystals that are depositied alongside collagen fibrils. |
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Appearance: Woven
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Primary, Immature
First bone to appear in embryonic development and during repair processes Random arrangement of collagen fibers Has more osteocytes and less mineralized than lamellar bone. Usually resorbed and replaced by lamellar bone (not much in adult) |
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Appearance: Lamellar
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Secondary, Mature
Begins to form one month after birth By age 4, most normal bone is lamellar Highly organized layers of osteocytes and collagen fibers Fewer osteocytes and more mineralized than woven bone |
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Architecture of Lamellar Bone: Compact (3)
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Circumferential Lamellae
Haversian System (Osteon) Interstitial Lamellae |
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Circumferential Lamellae
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Layers of bone formed around inner and outer circumferences of a bone
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Haversian System (Osteon)
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Concentric Lamellae (4-20) arranged around a canal.
Canal - Contains a blood vessel and loose CT. Lined with endosteum. Connected to adjacent canals through perpendicularly running Volkmann's canals |
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Interstitial Lamellae
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Incomplete Haversian systems that are left after resorption of the remainder of the osteon; located between complete Haversian Systems.
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Architecture of Lamellar Bone: Cancellous Lamellar Bone
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Thin trabeculae of lamellar bone with no Haversian Systems.
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Physical Properties of Bone
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Hard and Light
Resists Tensile, Compressive, and Shear Forces |
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Function of Bone (4)
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Houses bone marrow where blood cells are formed
Reservoir for calcium, phosphate and other ions that are released or stored in response to endocrine hormones Supports fleshy structures and protects vital organs Forms system of levers that multiply the forces generated during skeletal muscle contraction and transform them into bodily movements. |
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Aging: Bone - Structural Changes
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Btw 25 and 35 yrs, bone mass peaks. Afterwards the rate of resorption begins to exceed the rate of bone formation, resulting in decrease in bone mass.
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Aging: Bone - Functional Changes
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Enhanced bone fragility and consequent increase in fracture risk
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