The Basics of Skin

Skin is the outer covering of vertebrates. For humans, it is the largest organ of the integumentary system and functions as an insulator, temperature regulator, and it protects the organs. It can be oily, or dry, and is seen in a vast array of colours. Most of the human skin is covered with hair follicles, but it can also be hairless. Skin acts as a large sensor that keeps the brain in touch with the rest of the body with the use of numerous nerves.
There are three layers: epidermis, dermis, and the subcutis. The epidermis is the outermost layer. Keratinocytes formed from the protein keratin form layers that continually grow outward to replace the dead skin, the stratum corneum. The dermis is made of collagen and elastin fibres, and gives the skin its strength and elasticity. The nerve fibres are situated in this layer as well as the hair follicles. Finally, the subcutis creates a layer of fat cells that acts as a food reserve, and insulation and protection for internal organs.