Cartilage consists of chondrocytes embedded in a matrix, or ground substance, that comprises varying amounts of collagen.
Cartilage exists in several forms, from glassy to fibrous in appearance, and is capable of withstanding considerable pressure. Cartilage is commonly found in adults in the nose, ear, intervertebral disks, and tendons.
Types of cartilageThe simplest and commonest type of cartilage is hyaline cartilage, which is clear and glass-like. It joins the ends of the ribs to the sternum (breastbone), covers the ends of bones where these rub together at joints, and forms the lining of the trachea (windpipe).
Fibrous cartilage, or fibro-cartilage, is very tough and contains white fibers, but it is slightly elastic. It is found mainly in parts of the skeleton that are subject to extreme physical tension or compression. These include the disks between the bones of the backbone and the parts of tendons that are attached to the end of long bones.
Elastic cartilage contains yellow elastic fibers and is very elastic. The cartilage in the ear lobes and parts of the larynx is elastic cartilage.
Each mass of cartilage (except at the ends of bones) is surrounded by a sheath of tough connective tissue called the perichondrium. This sheath contains blood vessels from which food materials diffuse out to the cartilage cells. New cartilage cells are built up from the cells of the perichondrium. Cells on the inside of this layer break away and gradually turn into cartilage cells. They begin to secrete chondrin and each group of cells becomes separated by the accumulating matrix. A section through the cartilage shows that the cells near the edge are much closer together and less specialized than the older cells near the center.
Related category• ANATOMY AND PHYSIOLOGY
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