The human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system. The skin has multiple layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. Human skin is similar to that of most other mammals, except that it is not protected by a pelt. Though nearly all human skin is covered with hair follicles, it can appear hairless. There are two general types of skin, hairy and glabrous skin. The adjective cutaneous literally means "of the skin" (from Latin cutis, skin).
Because it interfaces with the environment, skin plays a key role in protecting the body against pathogens and excessive water loss. 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.
In humans, skin pigmentation varies among populations, and skin type can range from dry to oily. Such skin variety provides a rich and diverse habitat for bacteria which number roughly at 1000 species from 19 phyla.
There are at least five different pigments that determine the color of the skin. These pigments are present at different levels and places.
Melanin: It is brown in color and present in the germinative zone of the epidermis.Melanoid: It resembles melanin but is present diffusely throughout the epidermis.Keratin: This pigment is yellow to orange in color. It is present in the stratum corneum and fat cells of dermis and superficial fascia.Hemoglobin (also spelled haemoglobin): It is found in blood and is not a pigment of the skin but develops a purple color.Oxyhemoglobin: It is also found in blood and is not a pigment of the skin. It develops a red color.