Collagen

Collagen is the main protein of connective tissue in animals and the most abundant protein in mammals. It is one of the long, fibrous structural proteins; tough bundles of collagen called collagen fibers are the major component of the ECM that supports most, but collagen is also found inside certain cells. Collagen has great tensile strength, and is the main component of fascia, cartilage, ligaments, tendons, bone and teeth. Along with soft keratin, it is responsible for skin strength and elasticity. It strengthens blood vessels and plays a role in tissue development. It is present in the cornea and lens of the eye in crystalline form.

Collagen occurs in a number of forms (Type I-XVIII) that vary in their tensile strength and tissue localization. Rigid or flexible structure and structural changes in many body tissues are often a result of changes in collagen composition, as is cellular restriction and compartmentalization.