1. Honors Anatomy & Physiology Integumentary system

2. What are the ways skin protects the body? Essential question

3. functions: protecting the body helping to regulate body temperature allows you to sense stimuli in your environment stores blood synthesis of vit. D excretion & absorption of materials Integumentary system

4. skin = cutaneous membrane • largest organ of body • in adults: covers ~ 2 m² & weighs ~ 4.5 – 5 kg (10 – 11 lb) • 2 parts: • epidermis • dermis • sub Q below dermis & not technically part of skin: contains fat (insulation), & blood vessels, nerves that supply the skin Structure of the skin

5. Layers of the epidermis

6. keratinzed stratified squamous epithelium 4 main cell types: keratinocytes melanocytes Langerhans cells Merkel cells Epidermis

7. ~ 90% of all epidermal cells • produce fibrous protein: keratin: • protects skin & underlying tissue from • heat • microbes • chemicals • also release a water-repellant sealant from lamellar granules • decreases water entry/loss • inhibits entry of foreign materials keratinocytes

8. keratinocytes

9. ~8% of epidermal cells • produce melanin  keratinocytes • pigment (yellow-red to brown-black) that contributes to skin color • * absorbs UV radiation • “covers” nucleus in keratinocyte melanocytes

11. arise in red bone marrow then migrate to epidermis easily damaged by UV radiation function: immune response vs. microbes that invade Langerhans Cells

13. least numerous of epidermal cells (>1%) deep in epidermis in contact with Merkel disc (tactile disc) together detect different aspects of touch Merkel Cells

16. covers most of body 4 layers: stratum basale stratum spinosum stratum granulosum stratum corneum Thin Skin

17. found in areas where exposure to friction is the greatest • “thick” because has 1 extra layer: • stratum lucidum (between stratgumgranulosa & a thicker stratum corneum) Thick Skin

19. common & chronic skin disorder in which keratinocytes divide & move more quickly than normal from stratum basale stratum corneum • make abnl keratin  flaky, silvery scales @ skin surface • most often over knees, elbows, or scalp psoriasis

21. 2nd, deeper layer of skin composed mostly of CT 2 regions: papillary region reticular region Dermis

22. ~ 1/5th of total dermis • surface area greatly increased by finger-like structures: dermal papillae that project into epidermis • contain: • capillary loops • tactile receptors: Meissner corpuscles • free nerve endings (temp, pain, tickle, itch) Papillary region of dermis

24. develop during 3rd month of fetal development • pattern is genetically determined & unique to individuals (x identical twins) • on finger tips ridges deeper  finger prints • allow you to grasp things by increasing surface area Epidermal ridges

27. attached to subcutaneous layer beneath • contains: • dense irregular CT • hair follicles • sebaceous glands • sudoriferous (sweat) glands • collagen & elastic fibers (gives skin its elasticity, strength): extreme stretching  striae (stretch marks) Reticular region of dermis

30. 3 pigments contribute: Melanin Hemoglobin (hgb) Carotene Basis of skin color

31. made from a.a. tyrosine using enzyme tyrosinase then stored in organelle called a melanosome exposure to UV light increases enzymatic activity & more (& darker) melanin produced melanin absorbs UV radiation preventing it from damaging DNA which  skin cancer melanin

32. in RBCs  rosy color to lighter skinned individuals blushing: due to increased blood flow (autonomic nervous system at work) hemoglobin

33. yellow-orange pigment precursor of vit. A Carotene

34. inherited inability to produce melanin most due to cell’s inability to produce tyrosinase albinism

35. partial or complete lack of melanocytes from patches of skin produces irregular white spots ? Immune system malfunction? vitiligo

36. cyanotic: when blood not adequately oxygenated mucous membranes, nail beds & skin appears bluish Skin color as diagnostic clue

37. jaundice: due to build up of bilirubin (yellow pigment) in skin, sclera; usually indicates liver disease Skin color as diagnostic clue

38. erythema: redness of skin caused by engorgement of capillaries due to: injury, infection, inflammation, allergic reaction Skin color as diagnostic clue

39. pallor: paleness of the skin, seen in shock & anemia Skin color as diagnostic clue

41. all develop from embryonic epidermis • include: • Hair • Nails • Glands Accessory structures of the skin

42. present on most skin surfaces x palmar surfaces of hands, soles & plantar surfaces of feet genetic & hormonal influences determine the thickness & pattern of distribution of hair Hair (pili)

43. functions: • protection • scalp, eyebrows, eyelashes: from getting foreign objects in eyes • nose, ear canals: trap foreign objects • sensitive to light touch • touch receptors in hair root plexus hair

44. Anatomy of a hair

45. composed of columns of dead, keratinized cells bonded together by extracellular proteins hair

46. shaft: portion of hair that projects from scalp root: portion below scalp follicle: surrounds root of hair arectorpili: smooth muscle extends from side of hair follicle  superficial dermis Anatomy of a hair

47. lanuga: grows on fetus @ ~ 5 months fetal age; sheds b/4 birth vellus hair: short, fine hair that grows over baby @~ 2-3 months after birth terminal hair: coarse hair that develops after puberty Types of hair

49. Hair growth cycle

50. mostly due to amt & type of melanin in keratinzed cells dark hair has eumelanin blondes & redheads have pheomelanin gray: loss of melanin white: loss of melanin + air bubbles in shaft of hair Hair color