High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! The skin is a soft outer covering of an animal, in particular a vertebrate. Other animal coverings such the arthropod exoskeleton or the seashell has different developmental origin, structure and chemical composition. The adjective cutaneous literally means "of the skin" (from Latin cutis, skin). In mammals, the skin is the largest organ of the integumentary system made up of multiple layers of ectodermal tissue, and guards the underlying muscles, bones, ligaments and internal organs. Skin of a different nature exists in amphibians, reptiles, birds.