Integumentary System

1. Integumentary System

2. Integumentary System • Largest organ • Seen everyday • Spend great deal of time on it • Problems can often be seen here first

3. Integumentary System • 2 major components • cutaneous membrane • skin • accessory structures • hair • nails • exocrine glands

4. Cutaneous Membrane • outer epidermis • underlying dermis • accessory structures begin in dermis & protrude through epidermis to surface • deep to dermis is loose connective tissue in subcutaneous layer-hypodermis

5. Functions • Protection • abuse, abrasions, microorganisms, irradiation & chemicals • first line of protection against these irritants • Excretion • exudessalts, water & organic wastes • Maintains body temperature • insulates & cools • Vitamin D3 synthesis • essential for Ca++ metabolism • Storage • storeslipids in adipose tissue in dermis & subcutaneous layers • Detection • contains sensory receptors for touch, pain, pressure & temperature

6. Epidermis • stratified squamous epithelium • protective barrier against ultra-violet light, bacteria, chemicals & abrasion • 4-5 layers • 4-thin skin • 5-thick skin

7. Layers of Thick & Thin Skin

8. Stratum Basale/Stratum Germinativium • separates epidermis from dermis • dermal papillae-extend between adjacent epidermal ridges • one row of cuboidal to columnar shaped-large, basal or germinative cellsdividereplace superficial keratinocytes • 10-25% cells are melanocytes • have long branching processes that extend, reaching into stratum spinosum • Merkel cell–tactile receptor • sensitive to touch

9. Stratum Spinosum • main cell type-keratinocyte • cells may continue to divide • Langerhans’ (epidermal dendritic) cells • immune response

10. Stratum Granulosum • grainy layer • cells do not divide • begin to secrete keratin • as cells are pushed upward, away from source of nutrition, they gradually die-become keratinized • as keratin fibers develop cells become thinner & flatter • nuclei & other organelles disintegratecell dies • further dehydration produces tightly interlocked layer of cells made of keratin fibers surrounded by keratohyalin

11. Stratum Lucidum • clear layer • cells appear clear-because of a keratin precursor • found only in thick skin-soles & palms • cells are flattened, densely packed & filled with keratin

12. Stratum Corneum • outermost layer • dead, flat, keratinized cells • 25-30 layers • sloughed off • Keratinization or cornification • formation of protective, superficial layers of cells filled with keratin • dry & more or less waterproof-resists surface evaporation-prevents excessive water loss • found on all exposed surfaces except anterior surface of eyes • dead cells are connected by desmosomes-so tight-shed in groups • takes 15-30 days for cell to move from s. germinativium to s. corneum • dead cells remain in s. corneum 2 weeks before being shed • surface maintained by coating it with lipid secretions from sebaceous glands

13. Dermis • Between epidermis & hypodermis • Dense, irregular connective tissue • Stretches & recoils • Thicker than epidermis • Divided into papillary & reticular layers

14. Dermis • Papillary layer • closest to epidermis • areolar tissue • Reticular layer • deeper & thickestlayer • dense irregular connective tissue • contains thick bundles of interlacing collagen & elastic fibers • collagen give strength & ability to stretch • elastic stretch & recoil to original length

15. Dermis • dermal papilla are found here • project into epidermis • some contain touch receptors-Meissner’s Corpuscles (tactile corpuscle) • some have free nerve endings • detect pain, coolness, itching & tickling

16. Hypodermis not art of the skin stabilizes skin’s position while allowing for independent movement consists of adipose tissue & areolar tissue protectivefunctions-stores fat, helps prevent heat loss & acts as a shock absorber contains sensory endings for touch- lamellatedcorpuscle for deep pressure

17. Skin Color

18. Skin Color • Epidermal Pigmentation • Melanin • Carotene • Dermal Circulation

19. Epidermal Pigmentation Carotene • orange-yellow pigment which accumulates in epidermal cells • most apparent in s. corneum Melanin • brown, yellow-brown or black pigment • made by melanocytes in s. germinativium • travels in melanocyte processes & is transferred to keratinocytes • protects epidermis & dermis from UV radiation • melanocytes respond to UV exposure by increasing their activity • after UV exposure, melanin synthesis accelerates slowly peaking about 10 days after initial exposure • difference in skin color is due the amount made

20. Dermal Circulation • blood contains RBCs which contain hemoglobin-red pigment • binds & transports O2 • when bound to O2bright red • blood vessels in dermis take on reddish tint-when dilated • circulatory system decreasesskinpale-may turn white • sustained reduction in circulatory system-tissue O2 decreases hemoglobin releases O2turns darker red-seen from surfacebluish-cyanosis

21. Accessory Structures • Hair • Sweat Glands • Sebaceous Glands • Nails • Teeth Enamel • located in dermis & project through epidermis to surface

22. Hair • projects above surface of skin • almost everywhere except sides & soles of feet & palms, sides of fingers, toes & lips • first appears-5 months prenatally • larugo-fine, unpigmented & shed before birth • replaced by vellus or terminal hair • Vellus-fine body hair • Terminal-coarser, heavy, deeply pigmented hair found on the scalp, eyebrows, etc • Primary function-protection

23. Hair • produced in hair follicle • bag which extends into dermis • where it expands formshair bulb • hair root • anchors hair into skin, beginning at base of the hair at the bulb • hair shaft • projects from surface • cuticleconsists of layer of dead keratinized cells which overlap like shingles on a roof • Medulla • core-2-3 rows of cells containing pigment, air spaces & soft keratin • extension of dermal tissue at base-papilla protrudes inside the hair bulb • contains capillaries & nerves. • associated with each hair follicle is a tiny band of smooth muscle-arrector pili • -

24. Skin Glands • specialized epithelial cells • Exocrine • secrete sweat, oil & wax

25. Sweat Glands Sudoriferous glands coiled tubes in dermis with ducts leading to surface Apocrine armpits & anogenital area sticky, cloudy, potentially odorous secretion begins secreting at puberty Eccrine more numerous &widely distributed Functions cools surface of skin helps regulate body temperature prevents overheating protects from environmental hazards dilutes harmful chemicals discourages microorganism growth

26. Types of Sweat Sensible Perspiration • felt as moisture Insensible Perspiration evaporates before being felt Thermoregulatory Sweating Emotional Sweating Cold sweat

27. Sebaceous Glands • oil glands • secrete sebum (seb = oil) • mixture of triglycerides, cholesterol, proteins & electrolytes • usually secreted into hair follicle in a few regions-lips & mammary papilla & directly secreted onto skin surface of face, back & chest • Holocrine • entire gland dies when it secretes • Functions • inhibits bacterial growth • lubricates • protects keratin • conditions skin