Anatomy & Physiology I and II

Anatomy & Physiology Study Guide

©2018 Achieve Test Prep Page 70 of 367 6.4 Burns and Grafts Burns are significant injuries in that they can potentially damage large areas of the skin. The severity of the burn depends on the depth of penetration and the total area affected. With first and second- degree burns, the damage is restricted to the superficial layers of the skin. Only the surface of the epidermis is affected by first-degree burns. The entire epidermis, and perhaps portions of the dermis, are damaged by second-degree burns; however, hair follicles and glands are usually not affected. Third-degree burns destroy the epidermis and dermis and further extend into the subcutaneous tissue. The skin will typically blister. Burns that cover more than 20% of the body are life threatening because they affect fluid and electrolyte balance, the body’s thermoregulation system, and compromise the body’s ability to protect itself from infection. Widespread bacterial infection, or sepsis , is the leading cause of death in burn victims. A quick method used by medical professionals in determining the severity of burns is called the Rule of Nines . When using this method, the human body is divided into multiples of nine. The rule is modified for children, due to their proportional difference. 6.5 Aging Aging affects all the components of the integumentary system. The epidermis thins as germinative cell activity declines, and the connections between the epidermis and dermis weaken. These changes make older people more prone to injury, skin tears, and skin infections. The number of dendritic (Langerhans) cells decreases to about 50 percent of levels seen at maturity (roughly age 21). This decrease may reduce the sensitivity of the immune system and further encourage skin damage and infection. Vitamin D3 production declines by about 75 percent. The result can be reduced calcium and phosphate absorption, eventually leading to muscle weakness and a reduction in bone strength and density. Melanocyte activity declines, and in light-skinned individuals, the skin becomes very pale. With less melanin in the skin, people become more sensitive to exposure to the sun and more likely to experience sunburn. Glandular activity declines. The skin becomes dry and often scaly because sebum production is reduced. Merocrine sweat glands are also less active, and with impaired perspiration, older people cannot lose heat as fast as younger people can. Thus, elderly people are at greater risk of overheating in warm environments. The blood supply to the dermis is reduced. Reduction in blood flow makes the skin become cool, which in turn can stimulate thermoreceptors, making a person feel cold even in a warm room. However, because reduced circulation and sweat gland function in the elderly lessens their ability to lose body heat, overexertion or exposure to high temperatures (such as those in a sauna or hot tub) can cause body temperatures to soar dangerously high. Hair follicles stop functioning or produce thinner, finer hairs. With decreased melanocyte activity, these hairs are gray or white. The dermis thins, and the elastic fiber network decreases in size. The integument, therefore, becomes weaker and less resilient, and sagging and wrinkling occur.