Skeleton intervertebral discs. It is not as hard and rigid as bone but is stiffer and less flexible than muscle. Cartilage is composed of specialized cells called chondrocytes that produce a large amount of extracellular matrix composed of Type II collagen (except Fibrocartilage which also contains type I collagen) fibers, abundant ground substance rich in proteoglycan, and elastin fibers. Cartilage is classified in three types, elastic cartilage, hyaline cartilage and fibrocartilage, which differ in the relative amounts of these three main components. Unlike other connective tissues, cartilage does not contain blood vessels. The chondrocytes are supplied by diffusion, helped by the
Mineralized tissues site of mineralization in vesicles within specialized cells. Although they are in an amorphous mineral phase while inside the vesicles, the mineral destabilizes as it passes out of the cell and crystallizes. In bone, studies have shown that calcium phosphate nucleates within the hole area of the collagen fibrils and then grows in these zones until it occupies the maximum space. The organic part of mineralized tissues is made of proteins. In bone for example, the organic layer is the protein collagen. The degree of mineral in mineralized tissues varies and the organic component occupies a smaller volume as tissue