Lecture 03 Integumentary System

1. Lecture 03Integumentary System

2. Integumentary System = Skin + accessory organs • Cutaneous membrane • Epidermis – epithelial tissue • Dermis – connective tissue • Accessory Structures • Glands • Hair (hair follicles) • Nails • Deep to skin – not part of skin: • Hypodermis = subcutaneous (subQ) = superficial fascia:

5. Overview of Epidermis • Keratinized, stratified squamous epithelium • Contains no blood vessels • 4 types of cells • 4-5 distinct strata (layers) of cells • Thick vs. thin skin

6. Thick and Thin Skin • Thick – palms, soles • Thin – everywhere else – lacks Stratum lucidum • Hair folicles • Sebaceous glands • Sparser sensory receptors • Lacks epidermal ridges

7. Cells of the Epidermis Melanocytes – manufacture melanin- in Stratum Spinosum Keratinocytes – most abundant, undergo keratinization • Langerhans cells – macrophages which originate in bone marrow - in Stratum Spinosum • Merkel – associated with sensory neurons

8. Layers (Strata) of the Epidermis • Stratum corneum • Stratum lucidum * • Stratum granulosum • Stratum spinosum • Stratum basale *not in thin skin

9. Stratum germinativum Stratum spinosum Stratum granulosum Stratum lucidum* Stratum corneum Cell division, pigmentation, cuboidal 8-10 rows deep, many sides kerationcytes Cells dying, waterpoofing Clear, flattened, dead, fingertips only 25-30 rows deep, flattened, dead Layers of Epidermis

10. Skin Color • Determined primarily by melanin produced by melanocytes + physiologic condition • Two forms: • Phoemelanin which gives a yellow-red color to skin • Eumelanin – gives a black-brown color to skin • Also by carotene which interacts with eumelanin in Asian populations • Albinism/vitiligo – lack of pigment: all/patches

12. 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

13. Epidermal Ridges • Dermal Papillae: projections of dermal layer • Form in fetus as epidermis conforms to dermal papillae • fingerprints are left by sweat glands open on ridges • increase grip of hand • Increase contact between Stratum germinativum

14. Dermis • Deep to epidermis – connective tissue – What kind(s)? • Does not wear away • Contains blood vessels, adipose, various accessory structures • Composed of 2 layers • Papillary • Reticular

15. Papillary Region • Top 20% of dermis • Composed of loose connective tissue & elastic fibers • Finger like projections called dermal papillae • Functions • anchors epidermis to dermis • contains capillaries that feed epidermis • contains Meissner’s corpuscles (touch) & free nerve endings (pain and temperature)

16. Reticular Region • Dense irregular connective tissue • collagen and elastic fibers • aligned in cleavage lines • Contains interlacing collagen and elastic fibers • Packed with oil glands, sweat gland ducts, fat & hair follicles • Provides strength, extensibility & elasticity to skin • stretch marks are dermal tears from extreme stretching

17. Tattoos • Ink is injected into the dermis – hence the long lasting nature of tattoos

18. Accessory Structures of Skin • Epidermal derivatives • Cells sink inward during development to form: • hair • oil glands • sweat glands • nails

19. Hair • Hair –types – consisting of keratinized cells • Lanugo which develops during fetal development and disappears prior to birth • Vellus: fine hair which cover body • Intermediate • Terminal: hair of the scalp, eyebrows, eyelids • Hair develops from follicles which include: • Oil glands • Arrector pili: muscles which may pull on the follicle to cause the hair to stand on end in response to fear or cold • Hair root plexus: nerve endings surrounding the root which make the hair sensitive to touch • Hair growth: outwards from the matrix, a layer of cells in the root

20. Structure of Follicle • Shaft -- visible • medulla, cortex & cuticle • CS round in straight hair • CS oval in wavy hair • Root -- below the surface • Follicle surrounds root • external root sheath • internal root sheath • base of follicle is bulb • blood vessels • germinal cell layer Follicle

21. Cross section of follicle

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

23. Hair Related Structures • Arrector pili • smooth muscle in dermis contracts with cold or fear. • forms goosebumps as hair is pulled vertically • Hair root plexus (network of nerves) • detect hair movement • Sebaceous Glands • Produce oily secretion

24. Hair Growth • Growth cycle = growth stage & resting stage • Growth stage • lasts for 2 to 6 years • matrix cells at base of hair root producing length • Resting stage • lasts for 3 months • matrix cells inactive & follicle atrophies • Old hair falls out as growth stage begins again • normal hair loss is 70 to 100 hairs per day

25. 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

26. Glands of the Skin • Specialized exocrine glands found in dermis • Sebaceous (oil) glands • Sudiferous (sweat) glands • Ceruminous (wax) glands • Mammary (milk) glands

27. Sebaceous (oil) glands • Secretory portion in the dermis • Most open onto hair shafts • Sebum • combination of cholesterol, proteins, fats & salts • keeps hair and skin from soft & pliable • inhibits growth of bacteria & fungi(ringworm) • Acne • bacterial inflammation of glands • secretions stimulated by hormones at puberty

28. 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)

29. Structure of Nails • Tightly packed keratinized cells • Nail body • visible portion pink due to underlying capillaries • free edge appears white • Nail root • buried under skin layers • lunula is white due to thickened stratum basale • Cuticle • stratum corneum layer

30. Nail Growth • Nail matrix proximal to nail root produces growth • Cells transformed into tightly packed keratinized cells • 1 mm per week

31. 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

32. 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

33. 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

34. Burns • Destruction of proteins of the skin • chemicals, electricity, heat • Problems that result • shock due to water, plasma and plasma protein loss • circulatory & kidney problems from loss of plasma • bacterial infection

35. Types of Burns • First-degree • only epidermis (sunburn) • Second-degree burn • destroys entire epidermis & part of dermis • fluid-filled blisters separate epidermis & dermis • epidermal derivatives are not damaged • heals without grafting in 3 to 4 weeks & may scar • Third-degree or full-thickness • destroy epidermis, dermis & epidermal derivatives • damaged area is numb due to loss of sensory nerves

36. Skin Grafts • New skin can not regenerate if stratum basale and its stem cells are destroyed • Skin graft is covering of wound with piece of healthy skin • autograft from self • isograft from twin • autologous skin • transplantation of patients skin grown in culture

37. 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) • Examples • nitroglycerin (prevention of chest pain from coronary artery disease) • scopolamine ( motion sickness) • estradiol (estrogen replacement therapy) • nicotine (stop smoking alternative)

38. 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 • AND

39. What is the difference between thick and thin skin? • Where does each occur? • What are the layers of the epidermis? • … of the dermis? • What kind of tissue is found in each? • How do nails form? • Sketch a hair follicle – how does a hair grow? • What is a sebaceous gland – what is the purpose of their secretions?