Anatomy & Physiology

Anatomy & Physiology Study Guide These effects are most pronounced in areas of the body that have been exposed to the sun. With changes in levels of sex hormones, secondary sexual characteristics in hair and body-fat distribution begin to fade. Consequently, people age 90–100 of both sexes tend to look alike. Skin repairs proceed more slowly. Thus, whereas repairs to an uninfected blister might take three to four weeks in a young adult, the same repairs could take six to eight weeks at age 65–75. And because healing occurs more slowly, recurring infections may result. 6.6 Chapter Six Review An introduction to the integumentary system: • The integument, or integumentary system, consists of the cutaneous membrane or skin (which includes the epidermis and the dermis) and the accessory structures. Beneath the dermis lies the hypodermis, or subcutaneous layer. • Functions of the integument include protection, excretion, temperature maintenance, vitamin D3 synthesis, nutrient storage, and sensory detection. The epidermis is composed of strata (layers) with various function: • Thin skin, consisting of four layers of keratinocytes, covers most of the body. Heavily abraded body surfaces may be covered by thick skin containing five layers of keratinocytes. • The epidermis provides mechanical protection, prevents fluid loss, and helps keep microorganisms out of the body. • Cell divisions in the stratum germinativum, the innermost epidermal layer, replace more superficial cells. • As epidermal cells age, they pass through the stratum spinosum, the stratum granulosum, the stratum lucidum (in thick skin), and the stratum corneum. In the process, they accumulate large amounts of keratin. Ultimately, the cells are shed. • Epidermal ridges, interlocked with dermal papillae of the underlying dermis, improve the gripping ability of the palms and soles and increase the skin’s sensitivity. • Dendritic cells in the stratum spinosum are part of the immune system. Merkel cells in the stratum germinativum provide sensory information about objects that touch the skin. Factors influencing skin color are epidermal pigmentation and dermal circulation: • The color of the epidermis depends on two factors: dermal blood supply and epidermal pigmentation. • The epidermis contains the pigments carotene and melanin. Melanocytes, which produce melanin, protect us from ultraviolet (UV) radiation. • Interruptions of the dermal blood supply or poor oxygenation in the lungs can lead to cyanosis.

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