Understanding the Integumentary System and its Functions

1. Chapter 6Skin and the Integumentary System • Composed of several tissues • Maintains homeostasis • Protective covering • Retards water loss • Regulates body temperature • Houses sensory receptors • Contains immune system cells • Synthesizes chemicals • Excretes small amounts of waste

2. Types of Epithelial Membranes Mucous • line tubes and organs that open to outside world • lining of mouth, nose, throat, etc. • secrete mucus Serous • line body cavities that do not open to the outside • reduce friction • inner lining of thorax and abdomen • cover organs of thorax and abdomen • secrete serous fluid Cutaneous • covers body • skin Synovial • composed entirely of connective tissue • lines joints • Secretes synovial fluid

3. Skin Cells • help produce Vitamin D needed for normal bone and tooth development • some cells (keratinocytes) produce substances that simulate development of some WBCs

4. Layers of Skin • Epidermis • Dermis • Subcutaneous layer • beneath dermis • not part of skin

5. Epidermis • lacks blood vessels • keratinized • thickest on palms and soles (0.8-1.4mm) • melanocytes provide melanin • rests on basement membrane • stratified squamous

6. Production of new cells is balanced with the loss of dead cells • Protects underlying tissues against water loss, mechanical injury, and the effects of harmful chemicals • Epidermal cells keratinize and die as they are pushed to the surface

7. Epidermis Layers of Epidermis • stratum corneum (dead cells) • stratum lucidum • stratum granulosum • stratum spinosum • stratum basale (reproduce and grow)

9. Dermis • on average 1.0-2.0mm thick • contains dermal papillae • binds epidermis to underlying tissues • irregular dense connective tissue • muscle cells • nerve cell processes • specialized sensory receptors • blood vessels • hair follicles • glands

11. Subcutaneous Layer • hypodermis • loose connective tissue • adipose tissue • insulates • major blood vessels • binds skin to underlying organs

12. Hair Follicles • epidermal cells • tube-like depression • extends into dermis • hair root • hair shaft • hair papilla • dead epidermal cells • melanin • arrector pili muscle

13. A hair usually grows for a while, rests, and then is replaced by a new hair. • Hair color is determined by genes that direct the type and amount of pigment epidermal melanocytes produce • A bundle of smooth muscle cells forms the arrector pili muscle and attaches to each hair follicle • One or more sebaceous glands are attached to each hair follicle

15. Nails • protective coverings • nail plate • nail bed • lunula • made of specialized Epithelial cells that keratinize

16. Sebaceous Glands • usually associated with hair follicles • holocrine glands • secrete sebum • Excess sebum causes acne • absent on palms and soles

17. Sweat Glands • sudoriferous glands • widespread in skin • originates in deeper dermis or hypodermis Types • eccrine glands • apocrine glands • ceruminous glands • mammary glands

18. Eccrine sweat glands • Most numerous • Found on the forehead, neck, back, palms, and soles • Respond to elevated body temp or emotional stress • Sweat and sebaceous gland activity decreases with advancing age • Sweat is mostly water with salts and waste products

19. Apocrine Sweat Glands • Become active at puberty • Located in the axillary regions (armpit), groin, and around the nipples

20. Ceruminous glands are modified sweat glands that secrete earwax • Mammary glands are modified sweat glands that secrete milk

22. Regulation of Body Temperature • Regulation of body temperature is vital because heat affects the rates of metabolic reactions. Normal temperature of deeper body parts is close to a set point of 37°C (98.6°F). Skin plays a key role in body temperature homeostasis.

23. Heat production and loss • Heat is a by-product of cellular respiration. • The most active cells are skeletal and heart muscle cells and the liver. • If body temperature rises above normal: -more blood enters dermal blood vessels (vasodilation).

24. If body temperature rises above normal: • more blood enters dermal blood vessels (vasodilation). • deeper blood vessels contract (vasoconstriction) diverting blood to the surface and the skin reddens

25. heat is lost to the outside by: • radiation - rays move from warmer to cooler surroundings (primary way) • conduction - heat moves from warmer objects to cooler objects it is touching • convection - heated air moving away from the body • evaporation - fluid evaporates from the surface carrying heat away (sweating)

26. If the body temperature drops below normal: • dermal blood vessels constrict, causing the skin to lose color • sweat glands become inactive • if heat is lost excessively, skeletal muscles involuntarily contract increasing cellular respiration and producing additional heat.

27. Problems in Temperature Regulation Hyperthermia – abnormally high body temperature Hypothermia – abnormally low body temperature

28. If the air is saturated with water, sweat may fail to evaporate, and body temperature may remain elevated (hyperthermia) • Symptoms may begin with headache, dizziness, nausea, muscle cramping, and may lead to major organ failure • Lack of sweating – medical emergency

29. Hypothermia is lowered body temperature. • Symptoms begin with shivering, and leads to mental confusion, lethargy, loss of reflexes and ,consciousness, and eventually major organ failure

30. Skin Color • All humans have about the same number of melanocytes. Skin color differences are due to the amount of melanin produced

31. Genetic factors • Genes that control melanin production are inherited. • Dark skin is due to genes that cause large amounts of melanin to be produced • Lighter skin is due to genes that cause lesser amounts of melanin to form. • Mutant genes may cause a lack of melanin in the skin (albinism).

32. Environmental factors • Sunlight, ultraviolet light, and X rays darken existing melanin and stimulate more melanin production temporarily darkening the skin.

33. Physiologicalfactors • If blood is well oxygenated hemoglobin (blood pigment) is bright red causing the skin of light complected people to appear pinkish. • If oxygen content of blood is low hemoglobin is dark red and the skin appears bluish (cyanosis). • Dilated blood vessels can cause skin to redden

34. Constricted blood vessels cause a loss of reddish color. • Carotene in the subcutaneous layer may cause the skin to appear yellowish. • • Disease may affect skin color.

35. Healing of Wounds and Burns • Skin injuries trigger inflammation. Blood vessels dilate forcing fluids to leave and enter the damaged tissue. The affected area becomes red, warm, swollen, and tender.

36. Cuts • A shallow cut in the epidermis is filled in by reproducing epithelial cells. • Deeper cuts into the dermis or subcutaneous layer cause a clot to form. • platelets become entrapped in protein fibers (fibrin). • tissue fluids seep into the area • blood clot and dried fluids form a scab

37. fibroblasts begin to form new collagenous fibers that bind edges of the wound together • blood vessels extend beneath the scab • phagocytes remove dead cells • a scar where connective tissue replaces skin may appear

38. granulations (new blood vessel branch & fibroblasts) may form in large open wounds

39. Healing of Cuts

40. First degree burns (superficial partial-thickness burn) • only burns the epidermis • heals quickly with no scarring • the area is warm and red.

41. Second degree burns (deep partial-thickness burn) – • destroys some epidermis and dermis • blisters appear • area becomes moist and firm and varies in color from dark red to waxy white

42. healing depends on the accessory organs that survive • skin usually recovers with no scar tissue unless an infection occurs.

43. Third degree burns (full-thickness burns) • destroys the epidermis, dermis, and the accessory organs of the skin • injured skin may appear dry and leathery and varies in color from red to black to white • healing only occurs from epithelial cells growing inward from the margin of the burn

44. may require skin grafting: • autograft - thin layer of skin from unburned area is removed and transplanted in injured area • homograft - cadaveric skin is used to cover injury • skin substitutes - amniotic and artificial membranes human skin cultures - grow in lab and transplant • extensive scarring

45. Rule of Nines

46. Life Span Changes • Melanin production slows • Hair thins • Number of hair follicles decrease • Nail growth becomes impaired • Sensory receptors decline • Body temperature unable to be controlled • Diminished ability to activate Vitamin D • Skin becomes scaly • Age spots appear • Epidermis thins • Dermis becomes reduced • Loss of fat • Wrinkling • Sagging • Sebaceous glands secrete less oil

47. Clinical Application Acne Vulgaris • most common skin disorder • sebum and epithelial cells clog glands • produces whitheads and blackheads (comedones) • anaerobic bacteria trigger inflammation (pimple) • largely hormonally induced • androgens stimulate sebum production • treatments include antibiotics, topical creams, birth control pills