1. Integumentary System Chapter 5: The Skin

2. Integumentary System A. Consists of cutaneous membrane (skin) & accessory structures 1. cutaneous membrane *epidermis-superficial *dermis- underlying area of 2. accessory structures- hair, nails, exocrine glands, in dermis 3. hyperdermis (subcutaneous layer) lies beneath the dermis

3. 3. functions: protection from impact and abrasion excretion of salts & water Maintain temp- insulation or evaporation vitamin D synthesis & nutrition storage detection of touch, pressure, pain

4. B. Epidermis- consists of stratified squamous epithelium 1. avascular, rely on diffusion 2. active cells are near basal lamina due to short diffusion area. 3. Superficial cells are inert or dead. a. dominated by keratinocytes, form several layers, full of keratin 4. Types a. Thin skin- consists of 4 layers of keratinocytes, covers most of body b. thick skin -5 layers covers palms of hands and soles of feet c. Provides mechanical protection, prevents fluid loss, and protection from microorganisms

5. C. Layers of Epidermis 1. Stratum germinativum- inner most epidermal layer, cell division takes place, replacing superficial cells 2. Cell pass through:  stratum germinativum (base layer)  stratum spinosum (spiny layer)  stratum granulosum(grainy layer)  stratum lucidum (only in thick skin, clear layer)  stratum corneum (exposed surface) 3. Cells accumulate keratin during process, and eventually are shed. Process takes 15-30 days, w/ dead exposed cells remaining in s.corneum for 2 more weeks. Remember: g ermy s piney g ranny l ooks c orny

6. 4. Epidermal ridges- formed from the interlocking stratum germinativum and underlying dermis, which has projections ( dermal papillae )  provide ridges on palms and soles  increase skin’s sensitivity  ridge pattern is unique, doesn’t change during one’s lifetime, basis of finger prints 5. stratum. germinativum is dominated:  basal cells- stem cells whose divisions replace keratinocytes that are shed  Merkel cells provide sensory info about objects that come in contact w/ the skin  melanocytes provide pigment 6. Dendritic cells (Langerhans) in stratum spinosum stimulate defense against microorganisms and superficial skin cancers

7. Section 5.2 A. Pigments in epidermis 1. Carotene and melanin a. Carotene is orange-yellow pigment that can be converted to vitamin A- needed for epithelia maintenance and eyes b. melanin- brown, yellow-brown, or black pigment, made by melanocytes in the s. germinativum and transfer pigments to keratinocytes

8. c. Melanin protects dermis and epidermis from effects of sun’s UV radiation-protect DNA d. Melanin increase in production in response to increase in exposure to sun, but synthesis is slow, so burns often occur 2. Dermal circulation gives dermis a reddish tint a. hemoglobin is bright red when bound to oxygen b. lack of oxygen can cause change in skin color- bluish color (cyanosis) c. jaundice- yellow color, liver is unable to excrete bile d. vitiligo- individuals lose their melanocytes (MJ)

9. 5.3 B. sunlight causes cells in s. spinosum and s. germinativum to convert a steroid in the epidermis to Vitamin D. 1. liver converts Vitamin D into a product used by the kidneys to synthesize the hormone calcitrol - which is needed for the absorption of calcium and phosphorus (not enough leads to impaired bone growth/ maintenance---rickets)-avoided w/ fortified milk 2. vitamin- nutrient that must be obtained from diet because body can’t make or doesn’t make enough

10. 5.4 C. Epidermal Growth Factor (EGF)- a peptide growth factors 1. promotes the division of germinative cells in s. germinativum and s. spinosum 2. accelerates keratin production 3. stimulates repair after injury

11. LE 5-3 Surface Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum germinativum Basal lamina Dermis

12. LE 5-2 Epidermis Relationship between the epidermis and dermis Dermal papilla Dermis Epidermal ridge Thin skin Stratum corneum Thick skin Basal lamina Dermis Stratum lucidum Dermal papilla Epidermal ridge

13. LE 5-1-0 Epidermis Papillary layer Dermis Reticular layer Subcutaneous layer (hypodermis) Hair shaft Pore of sweat gland duct Tactile corpuscle Sweat gland duct Hair follicle Lamellated corpuscle Nerve fibers Sweat gland Sebaceous gland Arrector pili muscle Cutaneous plexus Artery Vein Fat

14. 5.5 D. Dermis supports epidermis and has 2 layers: 1. superficial papillary layer : contains blood vessels, lymphatics, and sensory nerves that supply the epidermis. 2. reticular layer : consists of network of collagen and elastic fibers oriented to resist tension in the skin a. extensive distension of dermis can cause stretch marks b. pattern of collagen and elastic fiber bundles form lines of cleavage - significant in how cuts heal and scars form

15. 3. cutaneous plexus – network of arteries in subcutaneous layer, along border w/ reticular layer, small arteries travel toward epidermis, supplying structures in dermis a. on reaching the papillary layer, small arteries form the papillary plexus, provides blood to capillary loops that follow the contours of the epidermis b. contusion - trauma to the skin, bruise from rupture of dermal blood vessels

16. 4. sensory receptors detect both light touch and pressure a. tactile discs monitor Merkel cells in epidermis, epidermis also has sensory neurons that detect pain and temp. b. dermis contains: * tactile corpuscles- receptors sensitive to light touch (in papillae) * lamellated corpuscles- receptors sensitive to deep pressure and vibration (in reticular layer)

17. 5.6 E. Hypodermis (subcutaneous layer) 1. stabilizes the skin’s position against underlying tissues and organs a. indistinct boundary between subcutaneous and reticular layer b. superficial region contains large arteries and veins, contains fat ( adipose ) for insulation and shock absorption

18. LE 5-10 Exposed shaft of hair Subcutaneous adipose tissue External root sheath Root hair plexus Boundary between hair shaft and hair root Connective tissue sheath Arrector pili muscle Sebaceous gland Connective tissue sheath Internal root sheath Glassy membrane Cortex of hair Cuticle of hair Medulla of hair Hair root Connective tissue sheath Arrector pili muscle Sebaceous gland External root sheath Hair matrix Internal root sheath Glassy membrane Cortex of hair Cuticle of hair Medulla of hair Hair bulb Hair shaft Hair papilla Hair bulb Hair papilla

19. 5.7 F. Hair 1. nonliving structures-originate in organs called hair follicles. 2. Functions of hair: a. protect head from UV radiation b. cushion impact to the head c. insulate the skull d. in nose and ear, prevents entry of foreign material and insects e. eyebrows & eyelashes protect eyes 3. Each hair has a root and a s haft (exposed area). 4. Production begins at base of hair follicle, where mass of cells form the hair bulb. a. The bulb surrounds a small hair papilla- a peg of connective tissue containing capillaries and nerves. b. Superficial cells of hair bulb produce the hair, forming a layer called the hair matrix

20. c. basal cells near center of the matrix divide, producing daughter cells that are pushed towards the surface d. daughter cells closer to center of matrix form the medulla (core of soft keratin) e. those farther from the center form the cortex, an intermediate layer f. The outer most layer is the cuticle (made of hard keratin) which forms a superficial layer of dead cells that protects the hair.

21. 5. Hair follicle has layers too: a. internal root sheath - just around hair root and deeper portion of shaft, doesn’t extend entire length of follicle b. external root sheath - from internal root sheath to surface of skin c. glassy membrane- thickened clear layer wrapped in dense connective tissue sheath 6. types of hairs: a. vellus hairs (peach fuzz) b. terminal hairs- pigmented, heavy hairs 7. arrector pili muscle - can erect a single hair (goose bumps) function: increases thickness of coat in animals

22. 8. Hair growth cycle- hairs grow and shed, typically growing for 2-5 years and then shed. a. while growing, nutrients are absorbed into hair- analysis used to treat disorders, metal poisoning b. at the end of growth cycle, follicle becomes inactive, hair is termed a club hair c. follicle gets smaller, and connections between hair matrix and club hair break down. d. follicle produces a new hair when cycle restarts, so club hair is pushed to surface and shed. d. healthy adult loses 50-100 hairs/day, greater loss indicates dietary issues, stress, male pattern baldness

23. 5.8 G. Exocrine glands 1. sebaceous gland (oil glands) -discharges waxy sebum (mixture of lipids) into a lumen (open passage way of gland) and into hair follicle a. functions: *sebum inhibits growth of bacteria *lubricates/protects keratin of the hair shaft *conditions the surrounding skin b. keratin is tough, but dead cells become dry and brittle- *wash hair to remove sebum, add lipids (lotions and conditioners) c. sebaceous follicles -large sebaceous glands, not associated with hair: *discharge sebum directly onto epidermis- *on neck, back, face, chest * overproduction can increase acne

24. 2. sweat glands (sudoriferous glands): a. apocrine - secretion into hair follicles *located around the nipples, in armpits, pubic region *begin secreting at puberty b. merocrine (eccrine) *more numerous * widely spread on the body, *produce watery secretion (sensible perspiration is 99% water, contains some electrolytes- sodium chloride) * secrete directly onto skin * functions to cool the surface of the body * contains dermicidin, antibiotic peptide

25. 3. Specialized glands a. mammary -similar structurally to apocrine sweat glands b. ceruminous glands – modified sweat glands in ear * secretion combines with sebaceous gland secretions * making waxy cerumen which helps trap foreign particles

26. 4. Gland control- a. autonomic nervous system controls: *activation/deactivation of sebaceous glands & apocrine sweat glands *subconscious *affect all glands of that type, no regional control b. merocrine sweat glands: * more precisely controlled * amount & area of body can vary *primary function is thermoregulation

27. 5.9 H. Nails 1. keratinized epidermal cells a. function to protect dorsal surface of fingers & toes 2. nail body *visible portion of a nail *covers the nail bed *composed of dead, compressed cells full of keratin 3. nail root *where production occurs *is overlain by the cuticle (eponychium), portion of the s.corneum 4. free edge of nail *continues past the nail bed *extends over the hyponychium (area of thickened stratum corneum)

28. 5. underlying blood vessels give the nail its pink color *near root, vessels are obscured- leaving a white “moon”, or luluna

29. LE 5-13c Lunula Nail root Hyponychium Eponychium Proximal nail fold Nail body EpidermisPhalanx Dermis