At the end of this chapter, the learner will be able to:
Identify each layer of the skin and its components and discuss their functions.
Relate the function of each cell type to the overall function of the integumentary system.
Recognize the role of non-cellular components of skin in maintaining an integumentary system capable of healing.
Diagnose tissue injury based on the depth of skin loss.
Skin is an important part of one's personality and character; a lot can be learned by observing an individual's skin and its abnormalities. Wrinkles are an indication of one's mood, age, social habits, or overexposure to the sun. The skin color reflects one's ethnicity as a result of the melanin content; the skin texture can reflect one's life occupation that involves repeated mechanical forces or weather exposure. Skin reflects one's emotions as it moves fluidly with the underlying muscles and connective tissue. Skin abnormalities can be a response to a disease process, injury, allergy, or medication. But what does the skin have to do with wound healing? In order to be considered closed, a wound has to have full re-epithelialization, defined as new skin growth, and no drainage or weeping from the pores. An appreciation for the anatomy and physiology of the integumentary system and the skin's role in healing is needed to understand wound closure, complete with optimal aesthetics and function.
The skin is a complex, dynamic, multilayered organ that covers the body, making it the largest single organ. It comprises 15–20% of the total body weight; if laid out flat, the skin would cover a surface of 1.5–2 m2.1 Embedded in the layers are a plethora of cells, vessels, nerve endings, hair follicles, glands, and collagen matrixes, each performing a specific task that as a whole enables the skin to protect and preserve the rest of the body. Both the cellular and non-cellular components of the epidermis and dermis are described in TABLES 1-1 and 1-2.
TABLE 1-1Cellular Components of the Skin ||Download (.pdf) TABLE 1-1 Cellular Components of the Skin
|Cell Name ||Description ||Location ||Function |
|Keratinocytes—dead ||Flat, elongated, nonnuclear ||Stratum corneum of epidermis ||Provide mechanical strength2 |
|Squames ||Horny, cornified cells ||Surface of stratum corneum ||Sloughing layer of epidermis |
|Keratinocytes—living ||Polyhedral, slightly flattened ||Stratum spinosum of epidermis ||Synthesize keratin filaments; phagocytose the tips of melanocytes to release melanin; hold large amounts of water |
|Keratinocytes—living ||Flattened polygonal ||Stratum granulosum ||Keratinization at terminal differentiation of the epithelial cells |
|Eosinophilic cells ||Flat, no nuclei or organelles; densely packed keratin filaments embedded in a dense matrix ||Stratum lucidum (only in soles of the feet and palms of the hands) ||Provide dense, thick layer of skin |
|Melanocytes ||Round cell bodies with long irregular dendritic extensions ||Between the stratum ...|