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Integumentary System Help (page 2)

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By — McGraw-Hill Professional
Updated on Aug 18, 2011

Associated Structures of the Skin

Hair, nails, and three kinds of exocrine glands form from the epidermal skin layer. These structures develop as down-growths of germinal epidermal cells into the vascular dermis, where they receive sustenance and mechanical support.

The hair follicle is the germinal epithelial layer that has grown down into the dermis (Figure 5-2). Mitotic activity of the hair follicle accounts for growth of the hair. The shaft of the hair is the dead, visible, projecting portion; the root of the hair is the living portion within the hair follicle; and the bulb of the hair is the enlarged base of the root of the hair that receives nutrients and is surrounded by sensory receptors. The outer keratinized cuticle layer appears scaly under a dissecting microscope. Variation in the amount of melanin accounts for different hair colors. Each hair follicle has an associated arrector pili muscle (smooth muscle) that responds involuntarily to thermal or psychological stimuli, causing the hair to be pulled into a more vertical position. Hair on the scalp and eyebrows protects against the sunlight, hair in the nostrils and the eyelashes protect against airborne particles. Asecondary function of hair is as a means of individual recognition and sexual attraction.

Integumentary System

Nails are formed from the hardened, transparent stratum corneum of the epidermis. Nails serve to protect the digits and aid in grasping small objects. All lizards, birds, and mammals have some sort of hardened sheath (claw, talon, hoof, or nail) protecting their terminal phalanges.

The three types of exocrine glands are formed from the epidermal layer of skin.

  • Sebaceous glands: Oil glands, secrete acidic sebum, lubricate and waterproof the skin.
  • Sudoriferous glands are sweat glands. Eccrine glands, abundant on the forehead, back, palms, and soles, function in evaporative cooling. Apocrine glands, in the axillary and pubic regions, function at puberty as a sexual attractant.
  • Mammary glands are specialized sudiferous glands within the breasts of females. Secrete milk under hormonal influence.

Physiology of the Skin

Practice problems for these concepts can be found at:

Integumentary System Practice Problems

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