The integumentary system consists of the skin, hair, nails, glands, and receptors. Its main function is to act as a barrier to protect the body from the outside world. It also functions to retain body fluids, protect against disease, eliminate waste products, and regulate body temperature. In order to do these things, the integumentary system works with all the other systems of your body, each of which has a role to play in maintaining the internal conditions that a human body needs to function properly. The integumentary system has many functions, most of which are involved in protecting and regulating your body’s internal functions in a variety of ways: • Protects the body’s internal living tissues and organs • Protects against invasion by infectious organisms • Protects the body from drying out • Protects the body against abrupt changes in temperature • Helps dispose of waste materials • Acts as a receptor for touch, pressure, pain, heat, and cold • Stores water and fat • Helps in the production of vitamin D. Your 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 certain materials to work right, as well as means of communicating information to other parts of the body. Thus, the skin and other parts of the integumentary system work with other systems in your body to maintain and support the conditions that your cells, tissues, and organs need to function properly. 10 The skin is one of the first defense mechanisms in your immune system. Your skin has tiny glands that secrete sweat and oil. Those fluids help decrease the pH on the surface of your skin to help kill microorganisms. The enzymes in your sweat can digest bacteria. The skin works with the excretory system by the removal of dead cells and sweat, which contains waste products. Skin also works to release waste, including water, salts, and urea, a toxic substance formed in the body’s production of energy. Waste travels through the sweat gland and out of the body through sweat pores, which are located in the epidermis. By helping to synthesize and absorb vitamins A, D, E, and K, the integumentary system works with the digestive system to encourage the uptake of calcium from our diet. These substances enter the bloodstream though the capillary networks in the skin. The integumentary system also works closely with the circulatory system and the surface capillaries through your body. Because certain substances, such as hormones, 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). Capillaries near the surface of the skin open when your body needs to cool off and close when you need to conserve heat. Your skin plays a vital role in your body regarding the sense of touch. The nervous system depends on neurons embedded in your skin to sense the outside world. It processes input from your senses, including touch, and initiates actions based on those inputs. For example, when you 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 integumentary system also contributes to numerous physiological processes, especially those involved in the regulation of the body’s internal environment, to maintain stable conditions. Examples of the way that the skin helps in temperature regulation are changes in the pattern of blood supply to the skin and sweating. Other examples of physiological process involved in maintaining stable internal conditions are the regulation of the amounts of water and minerals in the body, the inhaling of oxygen, and the exhaling of carbon dioxide.