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47 Cards in this Set
- Front
- Back
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Skeletal CT
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specialized modification of ECM
cartilage & bone |
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Cartilage properties
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gel-like
avascular, aneural low metabolic rate |
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3 main types of cartilage
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hyaline
elastic fibrocartilage |
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Hyaline cartilage cells
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Chondrocytes located in lacunae
Isogenic groups (result of mitoses) |
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Hyaline cartilage matrix
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Type II collagen fibrils (don't form fibers)
appear invisible (results in glassy appearance) Ground substance= hyaluronic acid, proteoglycans, glycoproteins |
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Hyaline cartilage territorial, interterritorial matrix
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territorial is immediately surrounding chondrocytes
interterritorial is between isogenic groups |
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Why does territorial matrix stain darker than interterritorial?
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T has lower conc. of collagen fibers and more acidic groups on the proteoglyans, so more basophilic
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Perichondrium
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Chondrogenic layer (w/chondroblasts)
Fibrous layer (dense irregular CT) not found on cartilage surfaces of joints |
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Two methods of cartilage growth?
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Interstitial- division of cells w/in cartilage, secretion of new matrix around chondrocytes
Appositional growth- chondroblasts lay new cartilage from w/in perichondrium- produces new matrix @ surface-- doesn't occur w/in fibrocartilage |
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Hyaline function/location
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1.Flexible structural support: trachea, larynx, costal cartilages
2. Smooth, firm surface: articular surfaces of joints 3. Provisional model for bone growth |
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Elastic Cartilage
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Chondrocytes embedded in matrix identical to hyaline except that it has elastic fibers
Appositional/interstitial growth |
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Elastic cartilage locations
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Auricle of ear, EAM, eustachian tubes, laryngeal cartilages
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Fibrocartilage
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Chondrocytes in lacunae
matrix contains bundles of Type I collagen NO perichondrium |
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Fibrocartilage locations
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IV discs (annulus), symphysis pubis, ends of tendons/ligaments
places where resiliance and tensile strength are needed |
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Bone
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Rigid
highly vascular metabolically active |
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Diaphysis
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shaft of compact bone & marrow cavity
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Epiphysis
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expanded end of long bone, covered w/compact bone and cartilage (articular surface)
interior is spongy bone |
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Marrow cavity
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hollow center of bone containing hematopoeitic tissue
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Epiphyseal plate
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hyaline cartilage plate between epiphysis and diaphysis (growth plate)
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Periosteum
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osteoprogenitor cell alter and fibrous CT layer
appositional growth of bone (osteoblasts) or resorption (osteoclasts) |
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Endosteum
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osteoblasts/osteoclast lining of marrow cavity and bone spicules
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Sharpey's fibers
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bundles of collagen fibers (continuous w/periosteum) that penetrate into bone
located @ attachment sites of tendons and ligaments |
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Flat bone structure
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Inner and outer table (compact bone)
Central diploe (spongy bone) |
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Osteoprogenitor cells
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partially differentiated mesenchyme (can undergo mitosis or differentiate further into osteoblasts)
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Osteoblasts
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Mononucleated cells that synthesize bone matrix and regulate mineral deposition
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Osteocytes
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Mononucleated cells in lacunae
Interconnected via processes in canaliculi (w/gap jxns) |
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Osteoclasts
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Large, multinucleated
Derived from monocytes In reabsorption cavities Have ruffled border, acidification of matrix for decalcification |
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Organic component of bone matrix
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For tensile strength
Collagen type I Ground substance |
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Inorganic component of bone matrix
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For compression strength
Hydroxyapatite crystals Citrate, carbonate, fluoride and Mg salts; bone localizing isotopes |
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How does appositional bone formation occur?
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Osteocytes lay down matrix, induce precipitation of hydroxyapatite crystals
These become embedded w/in lacunae/canaliculi |
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Woven v. lamellar bone
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Woven- laid down initially (embryonically) w/random collagen fibers
Later replaced by lamellar bone w/multiple layers. Collagen in each layer is parallel, but layers are oriented perpendicular to each other. |
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Lamellar bone:
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cirumferential lamellae (inner and outer)
concentric lamellae (haversian system) Interstitial lamellae |
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Osteon
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Haversian system
layer of osteogenic cells concentric lamellae continually remodelled |
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Are axes of osteons perp. or parallel to bone axis?
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parallel
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Volkmanns canals
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interconnections of osteons-
perpendicular to long axis of Haversian canal |
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Does spongy bone usually have osteons?
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No! but may be in some large trabecullae
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Intramembranous ossification
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Flat bones
osteoblasts differentiate from mesenchyme, lay down interconnecting spicules periosteal covering continues deposition woven bone initially, then replaced by lamellar |
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Endochondral ossification
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cartilage model formed (by interstitial or appositional growth)
bony collar generated by appositional growth hypertrophy-->death of chondrocytes-->calcification of matrix (primary center of ossification) |
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What lays down bone on the calcified cartilage? How does it get there?
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Osteoprogenitor cell lays down bone, carried by blood vessel
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Zones of endochondral ossification:
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Resting Cartilage
Proliferation Hypertrophy Calcified Cartilage Ossification |
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Where are secondary centers of ossification?
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Epiphyses
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What causes cessation of growth?
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Closure of epiphyseal plate
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Interstitial growth results in increased ____
Appositional growth causes increased_____ |
Interstitial increases length
Appositional increases width |
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Parathyroid hormone
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stimulates resorption (mobilization of calcium)
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calcitonin
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stimulates deposition (uptake of Calcium from blood)
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Where can deposition and resorption occur?
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Endosteal and periosteal surfaces
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What happens to fix a fracture?
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1. Periosteum/endosteum proliferation
2. Bony spicules/hyaline cartilage formation 3. Endochondral ossification forms callus (spongy bone) 4. Remodelled into compact or spongy, depending on location |
