Cartilage as the cricoid cartilage and carina. Cartilage is composed of specialized cells called chondrocytes that produce a large amount of collagenous extracellular matrix, abundant ground substance that is rich in proteoglycan and elastin fibers. Cartilage is classified in three types, "elastic cartilage", "hyaline cartilage" and "fibrocartilage", which differ in relative amounts of collagen and proteoglycan. Cartilage does not contain blood vessels (it is avascular) or nerves (it is aneural). Nutrition is supplied to the chondrocytes by diffusion. The compression of the articular cartilage or flexion of the elastic cartilage generates fluid flow, which assists diffusion of nutrients to the chondrocytes.
Shark anatomy Shark anatomy Shark anatomy has points of difference with the anatomy of bony and other types of fish. The large number of species and the diversity of shark habitats means that there are also variations on the "typical" shark's bodies. The skeleton of a shark is mainly made of cartilage. Most sharks have eight fins: a pair of pectoral fins, a pair of pelvic fins, two dorsal fins, an anal fin, and a caudal fin. The members of the order Hexanchiformes have only a single dorsal fin. The anal fin is absent in the orders Squaliformes, Squatiniformes, and Pristiophoriformes. Shark