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Abstract
This article, which forms part of the life sciences series, examines the anatomy and physiology of skin, also termed the integumentary system. Skin is composed of two main layers, the epidermis and dermis. The structure of the epidermis and dermis are described and their functions are discussed. Accessory structures, such as nails and hair are also considered. Although many diseases of the skin exist, two common conditions - psoriasis and decubitus ulcers - are described in this article.
Keywords
Anatomy and physiology, body systems, integumentary system, skin and skin disorders
The skin is a complex arrangement of structures with a range of different, but important, functions. The skin is composed of two main layers, the epidermis and dermis (Waugh and Grant 2010, Tortora and Derrickson 2009a). The subcutaneous layer is found beneath the dermis and is not considered part of the skin (Tortora and Derrickson 2009a).
Nurses need to be knowledgeable about what is considered to be healthy skin (Pringle and Penzer 2002). This is important, as the condition of the skin may often be a sign of underlying disease (Casey 2002). Changes in the skin may be one of the first indicators of an underlying health problem. Many nurses will be familiar with cyanosis where, because of poor delivery of oxygen to the tissues, the patient's skin appears blue.
Structure of the skin
The skin is the largest organ in the body, accounting for approximately 16% of the total body weight of an adult (Tortora and Derrickson 2009a). The skin weighs twice as much as the brain, approximately 3-5kg (Turkington and Dover 2007). Skin varies in thickness according to function and area of the body. On the eyelids, the skin is only 0.5mm thick, whereas it can be as much as 3-4mm thick on the soles of the feet (Brooker 1998). Skin is generally 1-2mm thick (Tortora and Derrickson 2009a).
The skin consists of thick outer layers, a widespread system of sweat glands sensitive to temperature changes and an extensive layer of fatty tissue under the surface of the skin. The skin also contains many cells that are sensitive to touch, pain, pressure, itching and temperature (Turkington and Dover 2007).
Epidermis
The epidermis is composed of stratified keratinised squamous epithelium (Tortora and...