Concepts of Human Anatomy & Physiology   5/e   Van De Graaff/Fox
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I. The Skin as an Organ

Concept: The skin is the largest organ of the body. Together with its associated structures (hair, glands, and nails), it constitutes the integumentary system. In certain areas of the body, skin has adaptive modifications that accommodate protective or metabolic functions. In its role as a dynamic interface between the continually changing external environment and the body's internal environment, the skin helps to maintain homeostasis.

II. Layers of the Skin

Concept: The skin consists of two principal layers. The outer epidermis is stratified into four or five structural layers, and the thick and deeper dermis consists of two layers. The hypodermis (subcutaneous tissue) connects the skin to underlying organs.

III. Physiology of the Skin

Concept: The skin not only protects the body from pathogens and external injury, it is a highly dynamic organ that plays a key role in maintaining body homeostasis.

IV. Accessory Structures of the Skin

Concept: Hair, nails, and integumentary glands form from the epidermal layer and are therefore of ectodermal derivation. Hair and nails are structural features of the skin and have a limited functional role. By contrast, integumentary glands are extremely important in body defense and maintenance of homeostasis.

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