Chapter 6

1. Chapter 6 Skin and the Integumentary System

2. Cutaneous Membrane • The cutaneous membrane is an epithelial membrane commonly called skin.

3. Cutaneous Membrane • Skin contains two layers, the epidermis and the dermis. Figure 6.2

4. Cutaneous Membrane • Beneath the dermis is loose connective and adipose tissue that binds the skin to underlying organs. This is the hypodermis or subcutaneous layer.

5. Skin • Skin is a protective covering that prevents harmful substances from entering the body. • Helps regulate body temperature and water loss. • It houses sensory receptors and contains immune system cells. • Synthesizes chemicals and excretes some wastes.

6. Epidermis • Composed of stratified squamous epithelium. Figure 6.3

7. Epidermis • Lacks blood vessels, but the deepest layer, the stratum basale, is close to the dermis and receives nutrients. • The thickness of the epidermis varies with region of the body.

8. Layers of the Epidermis • Stratum basale: deepest layer, single row of cells that divide and grow • Stratum spinosum: flat cells with keratin • Stratum granulosum: flat keratinized cells with shriveled nuclei • Stratum lucidum: clear cells • Stratum corneum: many layers of flat, dead, keratinized, nonnucleated cells that are shed

9. Melanin • A dark pigment produced by melanocytes. • Absorbs UV light and helps prevent mutations and damage to cells. Figure 6.4

10. Melanin • Melanocytes lie in the deepest layers of the epidermis. • Melanin is transferred from melanocytes to other epidermal cells

11. Dermis • Epidermal ridges project into the dermis. • These dermal papillae are responsible for fingerprints. • The dermis binds the epidermis to the underlying tissues. • Composed of irregular dense connective tissue with collagen and elastin

12. Dermis • Contains muscle fibers. Smooth muscles are associated with follicles and glands. • Motor and sensory nerves and sensory receptors are found throughout • Contains blood vessels, hair follicles, sebaceous and sweat glands.

13. Subcutaneous Layer • Or hypodermis is made up of loose connective and adipose tissue. • Collagenous and elastic fibers are continuous with those in the dermis. • The adipose tissue conserves body heat. • The subcutaneous layer contains the major blood vessels that supply the skin.

14. Hair Follicles • Hair develops from epidermal cells at the base of the hair follicle. • Epidermal cells divide, grow, and die. Figure 6.6

15. Hair Follicles • The dead cells make up the shaft of the hair. • The arrector pili muscle is a smooth muscle attached to the follicle.

16. Nails • Nails consists of a nail plate over the epithelium of nail bed on the skin surface. Figure 6.8

17. Nails • The white lunula at the base of the nail is the region of most active growth. • Epithelial cells divide and become keratinized.

18. Sebaceous Glands • Associated with hair follicles. • Sebum, a mixture of fatty material and cellular debris, is secreted to keep hair and skin soft and waterproof. • Acne results from excess sebum secretion.

19. Sweat Glands • Sweat glands or sudoriferous glands are epithelial glands widespread in the skin.

20. Sweat Glands • Glands respond to increased body temperature and function in evaporative cooling. Figure 6.11

21. Sweat Glands • Apocrine glands become active at puberty and secrete sweat that produces body odor when metabolized by bacteria. • Apocrine glands can respond to pain, fear, and emotions.

22. Modified Sweat Glands • Ceruminous glands secrete ear wax. • Mammary glands secrete breast milk.

23. Body Temperature Regulation • Radiation: Heat escapes from a warm surface to cooler surroundings. • Conduction: Heat is lost by moving directly into molecules of cooler objects. • Convection: Heat is lost as it is conducted to air molecules. • Evaporation: As sweat evaporates off the skin, it removes heat.

24. Problems in Temperature Regulation • Hypothermia or lowered body temperature is a dangerous condition resulting from cold exposure. • Hyperthermia or increased body temperature can result from inadequate body cooling during exercise or in extreme heat.

25. Figure 6.12

26. Skin Color • Heredity and environment determine skin color.

27. Skin Color • The number of melanocytes is the same in all races, but more melanin is released in darker skinned individuals. • People who inherit mutant melanin genes do not produce this pigment and have nonpigmented skin and hair, albinism.

28. Other Factors • UV light and X-rays stimulate melanocytes. • Oxygenated blood creates a pink tint to skin while lack of oxygen results in cyanosis where the skin appears bluish.

29. Other Factors • Carotene, found in yellow vegetables, can create a yellow or sallow tint to skin. • Jaundice due to liver malfunction can create a bright yellow color in the skin.

30. Skin Healing • Superficial cuts heal due to increased epithelial cell division. • Dermal cuts involve clotting and scab formation. Growth factors stimulate cell division and growth and scars may form.

31. Burns • Superficial partial-thickness (first degree) burns involve redness of the epidermis. • Deep partial-thickness (second degree) burns destroy the epidermis and some of the dermis. Fluid escapes causing blisters.

32. Burns • Full-thickness (third degree) burns destroy the epidermis, dermis, and accessory skin organs. • Treatment of burns involves estimating the burn surface area by the “rule of nines”.