Collagen

Collagen is a primary component of the connective tissue located in the dermis, the tough inner layer of the skin. This kind of connective tissue is also found in mucous membranes, nerves, blood vessels, and organs. Collagen in these structures imparts strength, support, and a certain amount of elasticity. As the skin ages, it loses some of its elasticity, resulting in wrinkles. Recently, injections of animal collagen given under the surface of the skin have been used to "plump up" the skin and remove wrinkles. However, this treatment is controversial. Many people develop allergic reactions to the collagen, and the procedure must be performed by a qualified physician.

Collagen is also a component of a kind of connective tissue that surrounds organs. This connective tissue encases and protects delicate organs like the kidneys and spleen.

Other locations where collagen fibers are prominent are in the tendons and ligaments. Tendons are straps of tough tissue that attach muscles to bones, allowing for movement. Ligaments are structures that hold the many bones of a joint, such as the knee joint, in proper position. Tendons and ligaments differ slightly in structure. In ligaments, the collagen fibers are less tightly packed than in tendons; in some ligaments, the fibers are not parallel.

Collagen adds strength to tendons and ligaments, and it imparts some stretch to these structures by allowing for some flexibility. However, collagen is not extremely elastic. If tendons and ligaments are stretched too far, these structures will tear, which may lead to problems in movement and bone position. Many athletes tear tendons and ligaments. When tearing occurs, the joint or bone in which the structures occur must be immobilized to allow for proper healing.

Cartilage is a connective tissue found in various places throughout the body, including the tip of the nose, the outside of the ears, the knees, and parts of the larynx and trachea. Cartilage consists of collagen fibers and cartilage cells. At these locations, collagen provides flexibility, support, and movement. Cartilage soaks up water like a sponge and is therefore somewhat "springy" and flexible. If the tip of the nose is pushed in and let go, it springs immediately back into place.