The Integumentary System

2.

The integumentary system consists of the skin, hair, nails, and sweat glands. 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.

Skin: First the skin protects the underlying structures by providing a physical barrier against the external environment. This can include anything from pathogens to abrasions. The skin helps to regulate temperature by perspiring when the body becomes too hot. When the body has become too cold, blood vessels near the surface of the skin constrict to prevent heat from leaving the body. Nerve fibers that run throughout the layers of the skin help us to sense

The skin assists in homeostasis. It does this by reacting differently to hot and cold conditions so that the inner body temperature remains more or less constant. Homeotherms (warm-blooded) maintain a constant body temperature regardless of the environment. In the skin of homeotherms, particularly in the scalp, palms, and soles of humans, there is a large blood supply in the form of arterio-venous plexuses that can deliver a huge amount of blood to the dermis of that area. The control of body temperature is dependent upon a negative feedback system to ensure that there is little fluctuation in the internal body temperature. Suppose you are in a place where environmental temperature is 101 degrees Fahrenheit, so that heat is continually flowing to your body, raising core temperature from the outside. Thermoreceptors in the skin and probably internally as well become stimulated by the increase in body temperature and create nerve impulses which serve as input to the control center. The control center, located in the hypothalamus of the brain, receives the input, integrates and interprets the information and then initiates two changes in the body. In response to output from the hypothalamus, there is increased eccrine sweat secretion and increased blood flow to the skin. Increased blood flow brings heat from the body core to the surface where it is lost by radiation and by evaporation of water; the net result is a decrease in body temperature. Return to homeostasis occurs when core body temperature is back within normal range, and the sweating-increased skin blood mechanism is turned off (the integumentary