Organization. The consistency of hyaline cartilage results from extensive cross-linking among its components. Link protein attaches the core proteins of proteoglycans to long chains of hyaluronic acid to form proteoglycan aggregates. The GAG side chains of the proteoglycans associate with type iI collagen fibrils. The chondrocytes are embedded in the matrix either singly or in isogeuous groups of 2-8 cells derived from one parent cell. The potential space occupied by each chondrocyte, called a lacuna, is visible only after the cell's death or after shrinkage during tissue processing. The chondrocytes at the core of a tissue mass are usually spheric; those at the periphery are flattened or elliptic. The matrix immediately surrounding the chondrocytes, called the capsular (territorial) matrix, is more intensely basophilic and PAS-positive than the intercapsular (interterritorial) matrix owing to the higher concentration of sulfated GAGs and lower concentration of collagen. Except for articular (joint) cartilage, all hyaline cartilage is surrounded and nourished by perichondrium. Articular cartilage is nourished by the synovial ffuid in the joint cavity.
Cartilage types: a)Hyaline Cartilage
1. Composition
Fibers, Hyaline cartilage matrix contains thin fibrils of type II collagen. Their small size and their refractive index (close to that of the ground substance) make them difficult to distinguish with the light microscope. Type II collagen contains a higher proportion of hydroxylysine than does type I. b. Ground substance, the predominant tissue component, comprises the following: (1) GAGs, mostly chondroitin sulfates and hyaluronic acid, with smaller amounts of keratan sulfate and heparan sulfate
(2) Proteoglycans, core proteins with GAG side chains;
(3) Proteoglycan aggregates proteoglycans covalently linked to long chains of hyaluronic acid by link protein;
(4) Glycoproteins, which attach various matrix components to one another and cells to the matrix, including link protein, fibronectin, chondronectin; and (5) Tissue fluid, an ultrafiltrate of blood plasma.
Fibers, Hyaline cartilage matrix contains thin fibrils of type II collagen. Their small size and their refractive index (close to that of the ground substance) make them difficult to distinguish with the light microscope. Type II collagen contains a higher proportion of hydroxylysine than does type I. b. Ground substance, the predominant tissue component, comprises the following: (1) GAGs, mostly chondroitin sulfates and hyaluronic acid, with smaller amounts of keratan sulfate and heparan sulfate
(2) Proteoglycans, core proteins with GAG side chains;
(3) Proteoglycan aggregates proteoglycans covalently linked to long chains of hyaluronic acid by link protein;
(4) Glycoproteins, which attach various matrix components to one another and cells to the matrix, including link protein, fibronectin, chondronectin; and (5) Tissue fluid, an ultrafiltrate of blood plasma.
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