Connective Tissue

Hierarchically constructed network of collagen fibers. Each collagen fiber consists of a large number of fibrils, which are each made up of pairs of three long protein molecules (tropocollagen) that are wound around one another in a helix. The individual protein molecules can be bound to varying degrees to one another with chemical bonds (cross-binding). The strength of the fibril increases with the number of bonds, making the connective tissue stronger. Strong muscles and muscles in older animals have more cross-binding in their connective tissues. Collagen is much weaker in fish than in terrestrial animals, but can be very strong in cephalopods.