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Integumentary System

Integumentary System. Honors Biology Power point for copying. Essential question. What are the ways skin protects the body?. Integumentary system. functions: protecting the body helping to regulate body temperature allows you to sense stimuli in your environment stores blood

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Integumentary System

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  1. Integumentary System Honors Biology Power point for copying

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

  3. Integumentary system • 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

  4. Structure of the skin • 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

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

  6. keratinocytes • ~ 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

  7. melanocytes • ~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

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

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

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

  11. psoriasis • 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

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

  13. Papillary region of dermis • ~ 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)

  14. Epidermal ridges • 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

  15. Reticular region of dermis • 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)

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

  17. melanin • 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

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

  19. Carotene • yellow-orange pigment • precursor of vit. A

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

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

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

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

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

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

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

  27. Hair (pili) • 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

  28. hair • 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

  29. Hair • composed of columns of dead, keratinized cells bonded together by extracellular proteins

  30. Anatomy of a hair • 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

  31. Types of hair • 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

  32. Hair color • 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

  33. Skin glands • exocrine glands ass’c with the skin: • sebaceous glands • sudoriferous glands • eccrine sweat glands • apocrine sweat glands

  34. Sebaceous glands • “oil” glands • most connected to hair follicles • rest secrete directly onto surface of skin (lips, eyelids, genitals) • secrete oily substance called sebum onto hair • keeps hair from getting brittle

  35. acne • inflammation of sebaceous glands colonized with bacteria • infection  cyst which destroys epidermal cells (cystic acne) • acne is not caused by eating chocolate or fried foods

  36. Sudoriferous glands • sweat glands •  sweat onto skin surface or hair follicles

  37. Ceruminous glands • modified sweat glands in external ear canal skin (subQ layer) • secrete cerumen (ear wax • provides a sticky barrier that impedes entrance of foreign bodies

  38. nails • plates of tightly packed, hard, dead, keratinized epidermal cells that form a clear, solid covering over the dorsal surfaces of the distal portions of the 20 digits • average growth ~ 0.04 in/wk • fingernails grow slightly faster than toe nails

  39. Functions of a nail • help us grasp & manipulate small objects • protect ends of digits • allows scratching

  40. Parts of exterior of a nail

  41. Parts of a nail • body: visible part • root: part buried • matrix: where cells divide to produce growth

  42. Functions of the skin (#7) • Thermoregulation • the homeostatic regulation of body temperature • skin achieves this in 2 ways: • sweating • evaporation of sweat requires nrg (body heat) so body cools down as sweat evaporates • adjusting flow of blood in dermis • vessels dilate when body too warm • vessels constrict when body too cold

  43. Functions of the skin 2. Blood Reservoir • skin carries ~ 8 – 10% of total blood flow in resting adult

  44. Functions of the skin 3. Protection • keratin protects underlying tissues • lipids released retard evaporation of water from skin surface • sebum moistens skin & has antibacterial properties • acidic pH of sweat bacteriostatic • melanin protects DNA in skin cells from UV damage • Langerhans cells alert immune system if microbes does attack / macrophages ingest microbes

  45. Functions of the skin 4. Cutaneous Sensations • skin contains variety of nerve endings & receptors • touch • pressure • vibration • tickle • pain • temperature

  46. Functions of the skin 5. Excretion • elimination of wastes from the body • only small amt substances excreted from skin • ~400 mL water/day • ~200 mL sweat (sedentary adult) • small amts salts, CO2, NH3, & urea

  47. Functions of the skin 6. Absorption • passage of materials from external environment  body cells • absorption of water-soluble materials negligible • lipid-soluble materials do absorb: • fat-soluble vitamins (A, D, E, K) • certain drugs (can be administered transdermally) • gases: O2 & CO2 • toxins: acetone, CCl4, salts of Hg, Pb, Ar, substances in poison ivy & poison oak

  48. Functions of the skin 7. Synthesis of Vitamin D • requires activation of a precursor molecule in the skin by UV rays in sunlight  modified by enzymes in liver & kidneys  producing calcitriol the most active form of vit. D • calcitriol: aids in absorption of calcium in GI tract

  49. Skin wound healing • skin damage sets in motion a sequence of events that repairs the skin to as normal as it can in both structure & function • depending on depth of wound 1 of 2 processes occur • epidemal wound healing • deep wound healing

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