The skin, the largest organ of the human body, forms a protective barrier for the other body systems. It maintains water within the body, helps to control body temperature, and protects against invasion of foreign objects, chemicals, and bacteria. In addition, nerves within the skin act as sensors that enable people to feel heat, cold, pressure and pain.
Skin is divided into three layers: the epidermis, dermis, and hypodermis. The outermost layer, the epidermis, mostly consists dead cells packed closely together. This outer layer is constantly being renewed by the cells that move to the surface and are shed in about four weeks. The dermis, the middle layer of the skin, consists of collagen fibers that make the skin tough and elastic. This layer has more nerve cells than any other layer of the skin and provides the body with sensory feedback (touch). It contains capillaries that provide the skin with nutrients and remove waste. The innermost layer, the hypodermis, is a vascularized layer consisting of mostly fat and connective tissue. It provides thermal insulation and protects the bones and joints from mechanical shock.
Artificial skin has been developed to assist in the treatment of burn victims. These are generally non-biological materials that cover the body to provide protection from outside elements, a three-dimensional structure (scaffold) into which the new cells can grow. The artificial skin is designed to biodegrade over time as it is replaced by natural tissue.
