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Sept. 24

Sept. 24. Quiz at the start of the lab period Cartilage General composition Function Types Perichondrium Formation Bone matrix. Cartilage. Chondrocytes Lacunae Extracellular matrix with GAGs and PGs, collagen, elastic fibers embedded in matrix Flexible, resist compression

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Sept. 24

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  1. Sept. 24 • Quiz at the start of the lab period • Cartilage • General composition • Function • Types • Perichondrium • Formation Bone matrix

  2. Cartilage • Chondrocytes • Lacunae • Extracellular matrix with GAGs and PGs, collagen, elastic fibers embedded in matrix • Flexible, resist compression • Shock absorber • Smooth surface for joint movement at articulating surfaces

  3. Types of cartilage • Hyaline, type II collagen (slender fibers, resists pressure) articular end of bones, trachea • Elastic cartilage, type II collagen (pinna, epiglottis) • Fibrocartilage, course dense type I cartilage, strong tensile forces (intervertebral discs)

  4. Perichondrium • Ct sheath surrounds most cartilage • Vascularized • Outer fibrous layer, inner cellular layer • Not next to synovial fluid

  5. Hyaline cartilage • Most common, blueish • Nose, larynx, bronchi, ends of ribs, joints

  6. Hyaline Cartilage: Histogenesis and growth of hyaline cartilage Mesenchymal cells retract processes -round up in chondrification centers Cells diffentiate into chondroblasts Start to secrete matrix -become trapped in lacunae

  7. Chondrocytes: • chondroblasts surrounded by matrix • Can still divide • Cluster in a lacuna called isogenous group • Cells then pushed away by forming matrix, called interstitial growth • Perichondrium formed by • -mesenchymal tissue at the periphery of hyaline cartilage forms • Fibroblasts and dense irregular connective tissue • Outer fibrous layer protects • Inner cellular layer has chondrogenic cells. • Growth by appositional growth

  8. Cartilage Cells: -chondrogenic cells, spindle shaped, babies (progenitors) -chondroblasts, from mesenchyme or chondrogenic of Inner cellular layer -plump basiphilic -chondrocytes, are chondroblasts surrounded by matrix, ovoid to round, Our sections create distortion

  9. Matrix of Hyaline Cartilage: • Type II Collagen, proteoglycans, glycoproteins, extracellular fluid • -semi-translucent blue gray color • -lots of collagen, same refractive index as the ground substance • Large PG molecules, aggrecans. • -protein cores, GAG molecules eg. Chondroitin 4 sulfate • -aggrecans link to hyaluronic acid • -these have negative charges, electrostatic interaction to sodium • The sodium attracts water molecules

  10. Condronectin • an adhesive glycoprotein • -similar to fibronectin, binds type II collagen, C4-sulfate, • Hyaluronic acid, integrins (transmb proteins) of chondrobasts • And chondrocytes. • Assists chondrocytes in maintaining contact with fibrous and • Ground substance in the matrix

  11. Elastic Cartilage: Similar to hyaline but has lots of elastic fibers in Matrix and perichondrium. -pinna, auditory tubes, epiglottis, larynx -usually have some hyaline around -perichondrial outer layer has lots of elastic fibers -matrix has lots of elastic fibers and type II collagen -very large chondrocytes -matrix not as ample as in hyaline cartilage -usually seen with orcein stain

  12. Fibrocartilage: -no perichondrium, type I collagen (acidophilic) -intervertebral discs, articular discs, attached to bone -parallel arrangement of chondrocytes Thick coarse collagen molecules parallel to tensile forces -chondrocytes derive from fibroblasts that form proteoglycans -intervertebral discsinterspersed with hyaline cartilage that covers the surface of the vertebra

  13. Bone Matrix: inorganic constituents Inorganic component: hydroxyapatite crystals (calcium and phosphate also amorphous) Water Associates with organic component: -type 1 collagen (highly cross-linked and hard to extract) makes bone acidophilic The hydroxyapatite + collagen give hardness and strength If decalcified, becomes soft If organic component is removed, remains hard but brittle.

  14. Bone, Amorphous ground substance -stains with PAS, explain glycosaminoglyacans staining with PAS -contains sulfated GAGs Keratin sulfate chondroitin sulfate chondroitin sulfate & keratin sulfate cross links with proteoglycans -> link proteins -> hyaluronic acid. These are called aggrecans composites

  15. Glycoproteins of the Bone Matrix Vitamin D is required for the synthesis of these glycoproteins. Osteocalcin binds hydroxyapatite Osteopontin binds hydroxyapatitie and integrins on osteoblasts & osteoclasts Sialoprotein binds matrix components and osteoblast and osteocyte integrins, therefore has and adhering function

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