When you finish this chapter you should be able to
Explain the structure and function of the skin and identify the lesions that result from skin abnormalities.
Describe in detail how skin trauma occurs, how it may be prevented, and how it may be managed.
Identify bacterial skin infections that are potentially contagious.
Describe the correct hygiene practices to use to avoid fungal infections.
Identify potentially threatening viral infections.
Contrast allergic, thermal, and chemical reactions of the skin.
Identify infestations and insect bites and contrast them with other skin infections.
It is essential that athletic trainers understand conditions that adversely affect the skin and mucous membranes, especially highly contagious conditions.133
SKIN ANATOMY AND FUNCTION
The skin is the largest organ of the human body. The average adult skin varies in total weight from 6–7½ pounds (2.7–3.4 kg) and is from –⅛ inch (0.031–0.125 cm) thick. It is composed of three layers: the epidermis, dermis, and subcutis (Figure 28–1 and Table 28–1).65
Cross section of the skin.
TABLE 28–1The Skin's Structure and Function |Favorite Table|Download (.pdf) TABLE 28–1 The Skin's Structure and Function
|Layer ||Subregion ||Function |
|Epidermis ||Stratum corneum || |
Prevents intrusion of microorganisms, debris, chemicals, and ultraviolet radiation
Prevents loss of water and electrolytes
Performs heat regulation for conduction, radiation, and convection
| ||Melanin (pigmentation) ||Prevents intrusion of ultraviolet radiation |
|Dermis || || |
Protects against physical trauma
Contains sensory nerve endings
Holds water and electrolytes
| ||Appendages ||Contains eccrine and apocrine sweat glands, hair, nails, and sebaceous glands |
|Subcutis || ||Stores fat and regulates heat |
The epidermis acts as a barrier against invading microorganisms, foreign particles from dirt and debris, chemicals, and ultraviolet rays, and it helps contain the body's water and electrolytes.38 The epidermis is the outermost layer of the skin and itself is composed of several layers identified as the stratum corneum, stratum granulosum, stratum spinosum, and stratum basale. The stratified nature of the epidermal cell layers results from the migration of keratinocytes, the epidermal epithelial cells, from the basal layer outward to the stratum corneum. During this migration process, the cells undergo a well-described change in shape from round basal cells to flat, elongated cells. In the final stage of differentiation, the flattened keratinocytes secrete a variety of substances into the extracellular space and then lose their nuclei to form the horny layer known as the stratum corneum. The stratum corneum acts as a permeability barrier, allowing only small molecules to diffuse into the lower regions of the epidermis, and thus it protects against environmental irritants, toxins, ...