1. PowerPoint ® Lecture Slides prepared by Janice Meeking, Mount Royal College C H A P T E R Copyright © 2010 Pearson Education, Inc. 5 The Integumentary System

2. Copyright © 2010 Pearson Education, Inc. The integumentary system (skin) Roles: Protection: from water loss from injury, chemicals and microorganisms. Keratin and epidermal desmosomes make skin a tough barrier to penetration and injury. The dry habitat of the skin and the acid secretions of sweat are unfavorable to microbial growth. a barrier to ultraviolet radiation

3. Copyright © 2010 Pearson Education, Inc. The integumentary system (skin) Roles: Vitamin D Synthesis UV rays in sunlight activate its synthesis Vitamin D is required for bone homeostasis Absorption The blood receives 1–2% of its oxygen through the skin. Many toxic compounds, as well as fat-soluble vitamins, can be absorbed through the skin

4. Copyright © 2010 Pearson Education, Inc. The integumentary system (skin) Roles: Sensory Functions - A variety of types of sensory nerve endings are present in skin Thermoregulation - regulate body temperature. When cold, dermal blood vessels constrict thus retaining heat in the body core. When hot, dermal blood vessels dilate, radiating heat to the surroundings. Perspiration allows evaporative cooling.

5. Copyright © 2010 Pearson Education, Inc. The integumentary system (skin) Roles: Blood Reservoir - The dermis houses about 10% of the body's blood vessels. Immunity - Langerhans cells (macrophages); interact with T-helper cells in immune responses. Excretion (minimal, most through kidneys) - urea; uric acid are lost through the skin pores in sweat.

6. Copyright © 2010 Pearson Education, Inc. Each skin layer has its own unique function: Epidermis - protection; Dermis - nourishment of epidermis; Subcutaneous layer - insulation.

7. Copyright © 2010 Pearson Education, Inc. Cells of the Epidermis Figure 5.2b Keratinocytes – produce the fibrous protein keratin that give the epidermis its protective properties Keratinocytes are the largest population of epidermal cells in the skin. They acquire their name through their function as warehouses for keratin, the protein which provides a physical barrier in the most superficial dead cells of the stratum corneum.

8. Copyright © 2010 Pearson Education, Inc. Cells of the Epidermis Figure 5.2b Melanocytes – produce the brown pigment melanin

9. Copyright © 2010 Pearson Education, Inc. Cell types - Melanocytes Melanocytes are located in the basal layer. In this location, they produce the pigment melanin Melanin is packaged into granules which are moved along dendritic processes and transferred by phagocytosis to adjacent keratinocytes. In the stratum corneum, melanin granules are uniformly distributed to form a UV-absorbing blanket which reduces the amount of radiation penetrating the skin.

10. Copyright © 2010 Pearson Education, Inc. The effect of sunlight on melanocytes UV radiation darkens the skin First by immediate photo-oxidation of melanin Second - over a period of days by stimulating melanocytes to produce more melanin. UV radiation also thickens the epidermis by inducing keratinocyte proliferation.

11. Copyright © 2010 Pearson Education, Inc. Skin Color Three pigments contribute to skin color Melanin – yellow to reddish-brown to black pigment, responsible for dark skin colors Freckles and pigmented moles – result from local accumulations of melanin Carotene – yellow to orange pigment, most obvious in the palms and soles of the feet Hemoglobin – reddish pigment responsible for the pinkish hue of the skin

12. Copyright © 2010 Pearson Education, Inc. Dermis Second major skin region containing strong, flexible connective tissue Cell types include fibroblasts, macrophages, and occasionally mast cells and white blood cells Composed of two layers : papillary – 20%, areolar CT, dermal papilae, meissner corpuscle Reticular - 80%, dense irregular CT, pacinian corpuscle

13. Copyright © 2010 Pearson Education, Inc. http://www.siumed.edu/~dking2/intro/IN038b.htm  Meissner's Corpuscle's located in dermal papillae;  found in the fingertips, palms, soles, eyelids, tip of tongue, nipples, clitoris, tip of penis.  Light touch

14. Copyright © 2010 Pearson Education, Inc. http://www.siumed.edu/~dking2/intro/IN039b.htm  Pacinian corpuscle's located in deep dermis and subcutaneous regions;  Populate areas in the joints, tendons, muscles, mammary glands, and external genitalia.  Pressure

15. Copyright © 2010 Pearson Education, Inc. Derivatives of the epidermis Glands Sweat glands Oil glands Hairs and hair follicles Nails

16. Copyright © 2010 Pearson Education, Inc. Sweat Glands Two main types of sweat (sudoriferous) glands 1.Eccrine (merocrine) sweat glands—abundant on palms, soles, and forehead Sweat: 99% water, NaCl, vitamin C, antibodies, metabolic wastes Ducts connect to pores Function in thermoregulation

17. Copyright © 2010 Pearson Education, Inc. Sweat Glands 2.Apocrine sweat glands – found in the axillary and anogenital areas Sebum: sweat + fatty substances and proteins Ducts connect to hair follicles Functional from puberty onward (as sexual scent glands?) Specialized apocrine glands Ceruminous glands—in external ear canal; secrete cerumen Mammary glands

18. Copyright © 2010 Pearson Education, Inc. Sebaceous (Oil) Glands Widely distributed Most develop from hair follicles Become active at puberty Sebum Oily holocrine secretion Bactericidal Softens hair and skin

19. Copyright © 2010 Pearson Education, Inc. Hair Protection Consists of dead keratinized cells Hair pigments: melanins (yellow, rust brown, black) Gray/white hair: decreased melanin production, increased air bubbles in shaft

20. Copyright © 2010 Pearson Education, Inc. http://i.ehow.com/images/GlobalPhoto/Articles/4731211/hair1_Full.jpg

21. Copyright © 2010 Pearson Education, Inc. Hair root  The hair root has three concentric layers of keratinized cells:  Medulla, consists of large cells and air spaces.  The cortex, a bulky layer surrounding the medulla, consists of several layers of flattened cells.  The outermost cuticle is formed from a single layer of cells that overlap one another from below like shingles on a roof

22. Copyright © 2010 Pearson Education, Inc. Hair Follicle A structure formed from both epidermis and dermis. The follicle is the point from which the hair grows. It is well supplied with small blood vessels, and the blood passing through them nourishes the growing region The follicle is composed of: A connective tissue root sheath derived from the dermis A basement membrane (glassy membrane) Inner epithelial root sheath derived from the epidermis Arrector pili Smooth muscle attached to follicle Responsible for “goose bumps”

23. Copyright © 2010 Pearson Education, Inc. Hair bulb The hair bulb lies inside the hair follicle. It is a structure of actively growing cells. New cells are continuously produced in the lower part of the bulb. As they grow and develop they steadily push the previously formed cells upwards.

24. Copyright © 2010 Pearson Education, Inc. Hair growth Hair grows by forming new cells at the base of the root. The cells move upward through the skin as new cells form beneath them. As they move up, they're cut off from their supply of nourishment and start to form a hard protein called keratin in a process called keratinization As this process occurs, the hair cells die. The dead cells and keratin form the shaft of the hair

25. Copyright © 2010 Pearson Education, Inc. Hair growth Each hair grows about 1/4 inch (about 6 millimeters) every month and keeps on growing for up to 6 years. The hair then falls out and another grows in its place. Follicles are active for 2 to 6 years; they rest for about 3 months after that. A person becomes bald if the scalp follicles die and no longer produce new hair. Thick hair grows out of large follicles; narrow follicles produce thin hair. Growth phase varies (6–10 years in scalp, 3–4 months in eyebrows)

26. Copyright © 2010 Pearson Education, Inc. Hair Thinning and Baldness Alopecia—hair thinning in both sexes after age 40 True (frank) baldness Genetically determined and sex-influenced condition Male pattern baldness is caused by follicular response to DHT

27. Copyright © 2010 Pearson Education, Inc. Structure of a Nail Scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes