Wilderness and Rescue Medicine 7th Edition Jeffrey Isaac, PA-C and David E. Johnson, MD

Chapter 16: Wounds and Burns

The skin is the largest of the body’s organs. It per- forms the remarkable function of protecting your sterile and sensitive internal organs from the flora, fauna, heat, and chill of the wild outdoors. It is also a major component of the thermoregulatory system. The skin is composed of several layers, the outer- most being the epidermis. The outer surface of the epidermis is called the stratum corneum, which is a layer of dead skin cells and bacteria. These cells are continuously being generated and shed at an impressive rate—some 50 million per day. This process, like the continuous flow of mucus from the respiratory system, is part of how we protect ourselves from the billions of microbes with which we share our existence

The dermis is the next layer; it contains larger blood vessels, sweat glands, hair follicles, and most of the nerve endings of the skin. Sweat and oil excreted onto the skin surface help with pro- tection by killing some bacteria and reinforcing the skin’s barrier effect. The total thickness of the dermal layer varies from a half of a millimeter on the eyelids to three or four millimeters on the palms and soles. The blood vessels in the dermis are capable of a dramatic change in volume as they constrict or dilate for thermoregulation or the need to maintain core perfusion pressure. When fully vasodilated, the skin can hold up to three liters of blood; when fully vaso-constricted, as in severe shell/core effect, the skin may retain as little as 30 milliliters of blood. Under the dermis is a layer of fat. In some places, like the buttocks or belly, this layer can be many centimeters thick. In other locations, like the back of the hand, it may be only a few cells thick. Below the fat lies a layer of tough connective tissue called fascia. This is typically dull-white and fibrous in appearance, and covers underlying muscle, bone, organs, and joints.

General Principles

Skin

STRUCTURE: • Epidermis/Dermis • Fat • Fascia FUNCTION: • Thermoregulation • Fluid retention • Protection from microbes PROBLEMS: • low risk wounds • cosmetic or functional • high risk wounds

1

Epidermis Dermis

Fat

Fascia

Muscle

*

©2018WMA