The skin is the outer covering of living tissue of an animal (or
plant). It is the largest organ of the integumentary system made
up of multiple layers of epithelial tissues, and guards the
underlying muscles, bones, ligaments, internal organs. The
adjective cutaneous literally means "of the skin" (from Latin
cutis, skin). Because it interfaces with the environment, skin
plays a very important role in protecting (the body) against
pathogens. Its other functions are insulation, temperature
regulation, sensation, synthesis of vitamin D, and the
protection of vitamin B folates. Severely damaged skin will try
to heal by forming scar tissue. This is often discolored and
depigmented. Skin has pigmentation, or melanin, provided by
melanocytes, which absorb some of the potentially dangerous
ultraviolet radiation (UV) in sunlight. It also contains DNA-
repair enzymes that help reverse UV damage, and people who lack
the genes for these enzymes suffer high rates of skin cancer.
One form predominantly produced by UV light