A hard but pliant substance forming parts of the skeleton – for example, the cartilages of the ribs, of the larynx and of the ears. Microscopically, cartilage consists of cells arranged in twos or in rows, and embedded in a ground-glass-like material devoid of blood vessels and nerves. The end of every long bone has a smooth layer of hyaline cartilage where it forms a joint with other bones (articular cartilage), while in young persons up to about the age of 16 there is a plate of cartilage (epiphyseal cartilage) running right across the bone about 12 mm (half an inch) from each end. The latter, by constantly thickening and changing into bone, causes an increase in length of the bone. (See also BONE.) In some situations there is found a combination of cartilage and fibrous tissue, as in the discs between the vertebrae of the spine. This fibro-cartilage combines the pliability of fibrous tissue with the elasticity of cartilage. (For cartilages of the knee, see KNEE.)