The skin stretches two square meters and weighs over 10 pounds! Waterproof yet permeable, protective yet sensitive, skin may best be described as the outer expression of inner health. The epidermal or integumentary system is susceptible to a variety of diseases, disorders, and injuries. These range from annoying but relatively benign bacterial or fungal infections that are categorized as disorders, to skin cancer and severe burns, which can be fatal.
The body is a complicated system that consists of many subsystems that help to keep it functioning properly. These subsystems serve a variety of purposes and require needed materials to function properly, as well as means of communicating information to other parts of the body. Thus, the skin and other parts of the epidermal or integumentary system work with other systems in the body to maintain and support the conditions that cells, tissues, and organs need to function properly.
The skin is one of the first defense mechanisms in the immune system. Tiny glands in the skin secrete oils that enhance the barrier function of the skin. Immune cells live in the skin and provide the first line of defense against infections. By helping to synthesize and absorb vitamin D, the epidermal or integumentary system works with the digestive system to encourage the uptake of calcium from our diet. This substance enters the bloodstream though the capillary networks in the skin. Healthy functioning of the skin also is related to the digestive system because the digestion and assimilation of dietary fats and oils are essential for the body to be able to make the protective oils for the skin and hair.
The epidermal or integumentary system also works closely with the circulatory system and the surface capillaries through the body. Because certain substances can enter the bloodstream through the capillary networks in the skin, patches can be used to deliver medications in this manner for conditions ranging from heart problems (nitroglycerin) to smoking cessation (nicotine patches).
The skin also is important in helping to regulate body temperature. If we are too hot or too cold, our brain sends nerve impulses to the skin, which has three ways to either increase or decrease heat loss from the body's surface: hairs on the skin trap more warmth if they are standing up, and less if they are lying flat; glands under the skin secrete sweat onto the surface of the skin in order to increase heat loss by evaporation if the body is too hot; capillaries near the surface can open when our body needs to cool off and close when we need to conserve heat.
The skin plays a vital role in our body as regards the sense of touch. The nervous system depends on neurons embedded in our skin to sense the outside world. It processes input from our senses, including touch, and initiates actions based on those inputs. For example, when we stub your toe, nerve cells in the foot send signals up the leg, through the spinal cord, and up into the brain. The nerve cell connections in the brain sense these signals as pain.
As well as interacting with the body systems as explained above, the epidermal or integumentary system also contributes to numerous physiological processes, especially those involved in the regulation of the body’s internal environment so as to maintain a stable condition. An example is provided by the way that the skin helps in temperature regulation by changes in the pattern of blood supply to the skin and by sweating, as mentioned above.