The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. The skin is composed of surface epithelium, exocrine components, connective tissue, muscles, and nerves. The primary role of the skin is to serve as a protective barrier between the internal body and the external environment; it also protects the body from excessive fluid loss.