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 acidApocrine glands: active at puberty, emotionally

upset, frightened, or in pain- axillary regions, groin

6.3 Regulation of Body Temperature- 98.6 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.