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4.1: Introduction to the Integumentary System
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The integumentary system refers to the skin and its accessory structures, and it is responsible for much more than simply lending to your outward appearance. In the adult human body, the skin makes up about 16 percent of body weight and covers an area of 1.5 to 2 square meters. In fact, the skin and accessory structures are the largest organ system in the human body.
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4.2: Layers of the Skin
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The skin is composed of two structurally distinct layers. These layers of differing cells and tissues are held to underlying structures by connective tissue. Together these layers provide that structure necessary for the overall functions of the integumentary system.
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4.3: Accessory Structures of the Skin
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Accessory structures of the skin include hair, nails, sweat glands, and sebaceous glands. These structures embryologically originate from the epidermis and can extend down through the dermis into the hypodermis.
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4.4: Functions of the Integumentary System
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The skin and accessory structures perform a variety of essential functions, such as protecting the body from invasion by microorganisms, chemicals, and other environmental factors; preventing dehydration; acting as a sensory organ; modulating body temperature and electrolyte balance; and synthesizing vitamin D. The underlying hypodermis has important roles in storing fats, forming a “cushion” over underlying structures, and providing insulation from cold temperatures.
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4.5: Diseases, Disorders, and Injuries of the Integumentary System
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The integumentary system is susceptible to a variety of diseases, disorders, and injuries. These range from annoying but relatively benign bacterial or fungal infections that are categorized as disorders, to skin cancer and severe burns, which can be fatal.