The human skin and its appendages like the hair follicles, nails and different glands make up the integumentary system. These structures work in conjunction with each other to perform a variety of functions that is broadly attributed to the skin. However, without the different appendages, the skin would not be as resilient and versatile as it is.
Functions of the Human Skin
The skin serves as a barrier against a number of mechanical, chemical, microbial and electromagnetic factors. Without this protective barrier functioning at its peak, the body would be bombarded by a number of insults in a day which could be fatal within minutes. This is achieved by the waterproof outer layer, the epidermis, and further supported by the underlying dermis. Various cells and structures within these two layers play a part in protecting the body, like the melanocytes which produce melanin to protect against ultraviolet light.
The nails also helps to protect the tips of the fingers and toes while these structures carry out its functions – handling objects (fingernails) and walking (toenails). Subcutaneous fat acts as a shock absorber thereby protecting the body against any impact.
The skin plays an integral role in maintaing the internal body temperature. Perspiration, alterations of blood flow through the skin and the hair follicles can either help to retain or dissipate heat. Subcutaneous fat, although not part of the skin structure, does provide an insulating layer to help retain heat.
Water and Electrolyte Balance
The skin prevents the loss of water and electrolytes from the internal environment and therefore helps to maintain homeostasis. It can also assist the kidneys in expelling excess water and waste products through sweat.
Vitamin and Hormone Synthesis
The two deeper layers of the epidermis, namely the stratum basale and stratum spinosum, are responsible for the synthesis of vitamin D. This vitamin has multiple functions, the most prominent of which is the regulation of calcium levels and its role in bone formation. Therefore the skin has an indirect effect on bone.
Certain appendages like the hair follicles play a role in converting small quantities of less active androgen into testosterone and also converts testosterone into DHT (5-alpha-dihydrotestosterone).
Sensation – Touch, Pain and Itch
The skin is an important medium for the tactile sensation. It allows the body to feel different sensations which play a role in a number of activities that help with daily functioning and even survival. The sense of touch even contributes to mental and emotional well being and interaction among humans in multiple ways that is not as yet fully understood.
The sensation of pain warns the brain that damage is ensuing and necessary steps must be undertaken to protect itself. The sensation of itch also serves as a warning signal that the skin is under “attack” from certain chemical factors and parasites, although itching may occur without any irritation to the skin surface.
The appearance of the skin has important psychosocial effects. It plays a part in physical attraction and tattoos and piercings may have a cultural importance. Hair removal, manicured nails and the use of cosmetics are all means to highlight the skin and its appendages which plays various roles in social interaction.
Pheromones secreted by the apocrine sweat glands may play a role in social interaction and sexual attraction. The exact role of pheromones, however, has not been conclusively identified.