Identify the following features in this higher magnification of hyaline cartilage of the trachea:
PERICHONDRIUM (a black bar) - a clear distinction between fibrogenic and chondrogenic zones is not apparent. Most of the cells appear to be fibrocytic. The cells adjacent to the cartilage show an increase in size and are properly termed chondroblasts unless they are within a distinct lacunae.
CELLS - Most chondrocytes are shrunken away from the sides of lacunae, leaving clear open lacunae (arrowhead), an artifact due to fixation. Notice the cell nests (arrowhead), some in pairs, some in tetrads. The increased staining intensity surrounding lacunae is the TERRITORIAL MATRIX.
Observe the transition in size from the smaller young cells at the periphery to the older larger cells in the center.
EXTRACELLULAR MATRIX (INTERCELLULAR SUBSTANCE) - The strong basophilic reaction (around arrowhead) of the intercellular amorphous substance is due to a high content of a sulfated glycosaminoglycans (chondroitin sulfuric acid). Collagen fibers, present as a dense felt-work similar to DICT, which make up the majority of INTERCELLULAR FORMED SUBSTANCE, are not visible since their refractive index is almost identical to that of the abundant amorphous substance. Chondrocytes have well developed RER for the synthesis of proteins which are present in the collagen fibers and a prominent GOLGI system for the production of carbohydrate components in the glycosaminoglycans in the form of PROTEOGLYCANS.
BLOOD VESSELS - Blood vessels are conspicuous by their ABSENCE. Nutrition is by diffusion of nutrients from perichondrial vessels through the gel-like substance of the matrix. Hyaline cartilage DOES NOT have a capillary bed within the matrix. The absence of blood vessels within the cartilage probably contributes to its notoriously poor capabilities of repair or regeneration.
