6.2 Accessory Organs of the Skin Nails: -Nail plate -Nail bed (under plate) -Lunula (moon-shaped region) covers the most actively growing region. -Cells become keratinized
Hair follicles: -Tube-like depression -Contains the hair root -Keratinized -Hair is composed of dead epidermal cells -Genes determine color: direct type and amount of pigment that epidermal melanocytes produce. -No pigment --- white hair
Pigment – trichosiderin: found only in red hair. Arrector pili muscle: attaches to each hair follicle. Muscle contracts, hair stands up. Goose bumps
Sebacceous glands: associated with hair follicles. Holocrine glands: secrete an oily mixture of fatty material and cellular debris called sebum. Keep the hair and skin soft, pliable, and waterproof.
Sweat Glands -Sudoriferous glands -Exocrine glands -Tiny tube that orginates as a ball-shaped coil. -Eccrine glands: most numerous, respond to body temperature. -Forehead, neck, back
Sweat contains: - water - urea - uric acid Apocrine glands: active at puberty, emotionally upset, frightened, or in pain - axillary regions, groin
6.3 Regulation of Body Temperature F or 37 C -Homeostatic mechanism -As body temp rises nerve impulses stimulate structures in the skin and other organs to release heat. -Hypothalamus – controls body temp.
Signals muscles of the wall of dermal blood vessels to relax. Vasodilation Eccrine sweat glands: become active Conserve heat: blood vessels constrict, weat glands become inactive. Shivering: requires an increase in the rate of cellular respiration and produces heat as a by-product.
80% of heat escape from the head.
6.4 Healing of Wounds -inflammation: red and swollen -Blood vessels dilate and become more permeable, forcing fluids to leave the blood vessels and enter the damaged tissues. -Provide the tissues with more nutrients and oxygen, which aids healing.
Scrap – epithelial cells along its margin are stimulated to divide more rapidly and fill in the gap. Cut into dermis or subcutaneous – blood vessels break, and the blood forms a clot in the wound, protects underlying tissues. Fibroblasts: migrate to area and form new collagenous fibers closing the wound.
Phagocytic cells remove dead cells and other debris.