The integumentary system is composed of the skin, hair, sweat glands, follicles, heat receptors and cold receptors. The integumentary system has a number of functions, many of them related to maintaining homeostasis (a stable internal environment).
The integumentary system acts as a first line of defense against microorganisms such as viruses and bacteria.
The skin also assists in the regulation of body temperature through sweating, which can serve to cool the body, or by provoking shivering which can raise the body temperature.
The integumentary system serves to protect the underlying tissues from exposure to the elements. It also provides a barrier against ultraviolet light by way of pigmentation.
The skin registers a variety of sensations ranging from pain to pressure and temperature (particularly cold).
The integumentary system is also partially responsible for the production of vitamin D, which is necessary for healthy bone development in children.