CHARACTERISTICS, COMPONENTS, AND CLASSIFICATION OF CARTILAGE TISSUE
Cartilage is a type of connective tissue composed of specialized cells called chondrocytes.
Chondrocytes are housed in small cavities wwithin the cartilagenous matrix called lacunae (singular: lacuna). The cartilage matrix has a distinctive composition and is more rigid than that of the connective tissue proper.
There are three types of cartilage tissue: hyaline cartilage, elastic cartilage, and fibrous cartilage or fibrocartilage. They differ mainly in the arrangement of their chondrocytes and especially in the composition of their ECM.
The collagen fibrils of the hyaline cartilage ECM are very thin, composed mainly of type II collagen. These fibrils are generally not organized into thick fibers and therefore can not be distinguished with a light microscope. The ECM of the elastic cartilage contains also a great amount of elastic material.
The fundamental ECM of the hyaline and elastic cartilage contains abundant proteoglycans, sulfated glycosaminoglycan molecules (e.g. chondroitin sulfate) and non-sulfated glycosaminoglycans (e.g. hyaluronan). They are primarily responsible for the firmness of cartilage.
As the molecules of the cartilage fundamental ECM, especially that of the hyaline cartilage have many acidic radicals, its sections are preferentially stained by blue/purple by hematoxylin and eosin.