1. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The integumentary system (skin) Roles:  protection  maintenance of normal body temperature  storage (of fat)  synthesis (of vitamin D)  excretion (of salts, water and wastes in sweat)  sensory perception

2. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings General Structure of the skin  Three distinct regions or layers compose the skin:  Epidermis - outermost layer; keratinized stratified squamous ET.  Dermis - inner layer; keratinized epithelium (hair follicles), glandular epithelium (sweat, sebaceous glands), dense irregular CT (collagen), smooth muscle tissue (arrector pili muscles), nervous tissue (Meissner's & Pacinian Corpuscles), and blood vessels.  Hypodermis (Subcutaneous) layer - adipose tissue; distinct layer beneath skin.

3. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Each skin layer has its own unique function:  Epidermis - protection;  Dermis - nourishment of epidermis;  Subcutaneous layer - insulation.

4. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Cells of the Epidermis Figure 5.2b  Keratinocytes – produce the fibrous protein keratin that give the epidermis its protective properties  Melanocytes – produce the brown pigment melanin  Langerhans’ cells – epidermal macrophages that help activate the immune system  Merkel cells – function as touch receptors in association with sensory nerve endings

5. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Layers of the epidermis  Stratum basale - innermost layer;  single layer of cuboidal youngest keratinocytes.  This layer is constantly undergoing cell division and produces new cells; also called stratum germinativum  contains melanocytes  Stratum spinosum - several spiky-like layers.  The cells divide relatively fast.

6. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Layers of the epidermis  Stratum granulosum  It is composed of 3-5 layers of flattened granular cells (filled with keratin); abundant granules  at the upper border of this layer the cells begin to die.  Stratum lucidum - composed of flattened dead keranocytes.  transparent band superficial to the stratum granulosum  Present only in thick skin

7. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Layers of the epidermis  Stratum corneum  Outermost layer of keratinized cells, consists of 20- 30 layers of cells  Accounts for three quarters of the epidermal thickness  Protective layer

8. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings http://sprojects.mmi.mcgill.ca/dermatology/epidermis.htm

9. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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  reticular

10. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Layers of the Dermis: Papillary Layer  Papillary layer – 20% of the dermis  Areolar connective tissue with collagen and elastic fibers  Its superior surface contains finger-like projections called dermal papillae  Dermal papillae contain capillary loops, Meissner’s corpuscles, and free nerve endings

11. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Layers of the Dermis: Reticular Layer  Accounts for approximately 80% of the thickness of the skin  Composed of dense irregular CT  Collagen fibers in this layer add strength and resiliency to the skin  Elastin fibers provide stretch-recoil properties  Contains the Pacinian corpuscle

12. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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

13. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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

14. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hypodermis  Subcutaneous layer deep to the skin  Composed of adipose and areolar connective tissue

15. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sweat Glands - Eccrine Glands (also called merocrine)  Structure - coil in deep dermis; duct in dermis  Characteristics - respond to elevated temperature / exercise; no odor in secretion; function throughout life; not associated with hair follicles;  Location - all over body  Secretion - water plus salts and wastes (urea and uric acid), oddorless  Mode of secretion – exocytosis (merocrine)

16. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Apocrine glands  Structure - ducts terminate into hair follicles.  Characteristics - respond to stress / emotions; odor in secretion; begin to function at puberty & continue through life; associated with hair follicles.  Location - armpits; genital areas;  Secretion - milky protein and fat-rich substance. Odorless but when combined with molecules on skin, takes the typical “sweat odor”  Mode of secretion – exocytosis (merocrine)

17. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Modified Apocrine Glands  Ceruminous glands - external ear; secretion - earwax;  Mammary glands - breasts; milk.

18. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sebaceous Glands  Location - found nearly all over skin; associated with every hair follicle  Secretion - sebum (i.e. oil and fragmented cells). Sebum is secreted into hair follicle;  Mode of secretion – holocrine (cells burst)  Secretion is stimulated by hormones especially androgens.  Function oily substance keeps skin & hair soft and moist and waterproof.

19. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings http://www.sweatmanagement.ca/UnderstandSW.asp

20. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hair Function and Distribution  Functions of hair include:  Helping to maintain warmth  protection  Hair is distributed over the entire skin surface except:  Palms, soles, lips, nipples and portions of the external genitalia

21. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  The shaft, which projects from the skin  Root or base is in deep dermis  Papilla – a small nipple of dermal tissue that enters into the hair bulb from the connective tissue sheath and provides nutrition to the growing hair.  Arrector Pili Muscle - a bundle of smooth muscle associated with every hair follicle; causes hair to stand on end ("goose bumps") when frightened or cold. Hair parts

22. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hair root  A hair 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

23. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 5.5c, d

24. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hair structure - Follicle  A structure formed from both epidermis and dermis.  The follicle is the point from which the hair grows. It is well supplied with minute 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

25. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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.

26. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Nails  Nails are derivates of the stratum corneum undergoing keratinization (active mitosis in lunula).  Functions: protection of digit ends.  Body the visible attached portion;  Free edge – the portion that grows away from the body;  Root – the part that is in the skin and adheres to an epithelial nail bed;  Nail matrix – the part of the nail bed containing germinal cells responsible for nail growth.

27. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Structure of a Nail Figure 5.6