Lecture 6: Integument

1. Lecture 6: Integument

2. Membranes Involve epithelia and connective tissues Where are these found/ What are their general characteristics? • Cutaneous - • Mucous – • Serous – • Synovial -

3. Skin – two distinct layers Epidermis – tissue type_____________ Number of layers: ________ Dermis – tissue type_____________ Number of layers: ________ Not part of skin but layer deep to the dermis – 3 names: _________________ _________________ _________________

4. Epidermis • 4 or 5 layers – depends on location • Thick skin – 5 layers – where? • Thin skin – 4 layers – elsewhere • Receives nourishment from dermis • Only deepest layer actively divides • Location of melanocytes – produce pigments giving skin color

5. What factors impact skin color? • Amount of melanin and other pigments– produced by melanocytes • Due to? • Blood flow near surface of skin • Physiological conditions –

6. Diagnostic Clues – Skin Color • Jaundice • yellowish color to skin and whites of eyes • buildup of yellow bilirubin in blood from liver disease • Cyanotic • bluish color to nail beds and skin • hemoglobin depleted of oxygen looks purple-blue • Erythema • redness of skin due to enlargement of capillaries in dermis • during inflammation, infection, allergy or burns

7. Appearance of Skin Color – Multifactorial Interaction of Genetic, Environmental and other factors • Deposition of melanin and other pigments due to activity of melanocytes – not number of melanocytes • Controls: • Genetic • environmental

8. Photodamage • Ultraviolet light (UVA and UVB) both damage the skin • Acute overexposure causes sunburn • DNA damage in epidermal cells can lead to skin cancer • UVA produces oxygen free radicals that damage collagen and elastic fibers and lead to wrinkling of the skin

9. Skin cancer – 2 types: melanoma and nonmelanoma • Nonmelanoma- 2 types – basal cell and squamous cell (the more dangerous type) • Melanoma – pigmented cells, a mole which has become malignant

10. Transdermal Drug Administration • Method by which drugs in a patch enter the body • Drug absorption most rapid in areas where skin is thin (scrotum, face and scalp) –why? • Examples • nitroglycerin (prevention of chest pain from coronary artery disease) • scopolamine ( motion sickness) • estradiol (estrogen replacement therapy) • nicotine (stop smoking alternative)

11. Dermis • Does not wear away • Composed connective tissue • Vascular • Sensory nerve endings • Contains some adipose • various accessory structures • Nails • Hair • glands • Composed of 2 layers

12. Sensory Receptors of the Skin • Largely in dermis – • Perception of touch, temperature, pain, pressure • Distribution varies • Naked nerve endings • Hair root plexuses • Merkel discs • Encapsulated nerve endings

13. Hair – • Three kinds: • Lanugo – usually disappears prior to birth • Vellus: _____________________ • Terminal: ___________________ • Hair develops from _______________ • Growth: outwards from the matrix • cycle = growth stage – 2-6 yrs • resting: ~ 3 months

14. Bulb surrounds papilla Division of cells at matrix results in hair growth

15. Hair Color • Result of melanin produced in melanocytes in hair bulb • Dark hair contains true melanin • Blond and red hair contain melanin with iron and sulfur added • Graying hair is result of decline in melanin production • White hair has air bubbles in the medullary shaft

16. Nails • Involve: free edge which you trim, the body and root • Growth is from the nail bed – specifically from the matrix; an area proximal to the root • Nail is tightly packed, keratinized cells (dead)

17. Site of growth - matrix • proximal to nail root produces growth • Cells transformed into tightly packed keratinized cells • Growth ~1 mm per week

18. General Functions of the Skin • Regulation of body temperature • Protection as physical barrier • Sensory receptors • Excretion and absorption • Synthesis of vitamin D

19. Skin Cancer • 1 million cases diagnosed per year • 3 common forms of skin cancer • basal cell carcinoma (rarely metastasize) • squamous cell carcinoma (may metastasize) • malignant melanomas (metastasize rapidly) • most common cancer in young women • arise from melanocytes ----life threatening • key to treatment is early detection watch for changes in symmetry, border, color and size • risks factors include-- skin color, sun exposure, family history, age and immunological status

20. Epidermal Wound Healing • Abrasion or minor burn • Basal cells migrate across the wound • Contact inhibition with other cells stops migration • Epidermal growth factor stimulates cell division • Full thickness of epidermis results from further cell division

21. Deep Wound Healing • If an injury reaches dermis, healing occurs in 4 phases • inflammatory phase has clot unite wound edges and WBCs arrive from dilated and more permeable blood vessels • migratory phase begins the regrowth of epithelial cells and the formation of scar tissue by the fibroblasts • proliferative phase is a completion of tissue formation • maturation phase sees the scab fall off • Scar formation • hypertrophic scar remains within the boundaries of the original wound • keloid scar extends into previously normal tissue • collagen fibers are very dense and fewer blood vessels are present so the tissue is lighter in color

22. Age Related Structural Changes • Collagen fibers decrease in number & stiffen • Elastic fibers become less elastic • Fibroblasts decrease in number • Langerhans cells and macrophages decrease in number and become less-efficient phagocytes • Oil glands shrink and the skin becomes dry • Walls of blood vessels in dermis thicken so decreased nutrient availability leads to thinner skin as subcutaneous fat is lost

23. THINGS TO WORRY ABOUT • Your Pores — Portals for Invasion? • Musty Dankness • Fleas & Ticks — Tiny TerroristsWhat's Embedded in Your Bed? • What Your Mother Never Told You About Those Hidden Corners and Cracks • Pink Mold — Slime or Scourge?Mildew — Mold's Evil Twin