lecture: the integumentary system

  1. integument (skin) information
    • LARGEST organ (most visible and accessible organ)
    • surface area: 1.5 - 2 m2
    • 15-20% of total body weight
    • first line of defense against environment
    • dead skin = billions of tons of dust in environment because shed 50,000 cells every minute (holy batman, im bathing in dead cells ... i dunno how to feel about that)
  2. 5 Functions of the integumentary system
    • 1. protection - Protects underlying tissues and organs, Serves as barrier against infection and injury, Provides protection against UV coming from the sun
    • 2. temperature regulation - helps regulate body temperature. Provides insulation to keep heat in and evaporative cooling to allow heat out.
    • 3. excretion - removes waste products from the body e.g. salts, water, and organic wastes by glands
    • 4. Vitamin D production
    • 5. sensations -detection of touch, pressure, pain, and temperature i.e. the skin contains several types of sensory receptors
  3. 2 structures of the integument (skin)
    • 1. skin (cutaneous layer) = epidermis + dermis
    • 2. accessory structures
  4. context: 2 structures of the integument (skin)
    3 layers of the skin (cutaneous layer)
    • 1. epidermis - superficial layer of epithelial tissue
    • 2. dermis - deep layer of connective tissue. provides nourishment of epidermis and provides structural strength (2 TYPES: papillary layer and reticular layer)
    • 3. hypodermis (subcutaneous layer) - technically not part of skin [OMG then WHYYYYY is it listed], it is loose connective tissue that connects skin to underlying structures and provide insulation
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  5. context: 2 structures of the integument (skin)
    accessory structures (3)
    • Originate in the dermis extend through the epidermis to skin surface:
    • 1. Hair
    • 2. Nails
    • 3. Glands
  6. context: 3 layers of the skin (cutaneous layer)
    • -avascular so nourished by diffusion from capillaries of the papillary layer of the dermis
    • composed of cells arranged into layers (strata) and is separated from dermis by basement membrane
  7. context: epidermis
    thick vs thin skin (this does not mean getting tougher metaphorically or psychologically)
    • 1. thick = 5 layers (strata) = 0.5mm-1mm thick
    • deep epidermal ridge patterns (increase surface area and provide friction; produce fingerprints)
    • location: covers palm of hands and soles of feet
    • 2. thin = 4 layers (strata) = < ~ 0.1 mm thick
    • most of body surface area
  8. context: epidermis
    5 layers (strata) of keratinocytes in thick skin
    • 1. stratum germinativum
    • 2. stratum spinosum
    • 3. stratum granulosum
    • 4. stratum lucidum
    • 5. stratum corneum
    • 15-30 days to reach corneum and stay for 2 weeks before shedding
  9. context: 5 layers (strata) of keratinocytes in thick skin
    • basal cells: stem cell source of keratinocytes (15 day journey to top layer)
    • Merkel cells: touch receptor cells (trigger nervous system) found in hairless skin
    • Melanocytes: secrete melanin (pigment) scattered through this layer
    • forms epidermal ridges: fingerprints here!!!
    • attached by hemidesmosomes to basal lamina
  10. context: 5 layers (strata) of keratinocytes in thick skin
    • immunity
    • "spiny layer"
    • Langerhans cells: anti-microbial (from bone marrow to work as macrophages in immune system)
    • 8-10 layers of keratinocytes
    • new daughter keratinocytes
  11. context: 5 layers (strata) of keratinocytes in thick skin
    • strength
    • "grainy"
    • 3-5 layers/high keratin fiber and keratohyalin (dense granules/aggregation and cross-linking of keratin)
  12. context: 5 layers (strata) of keratinocytes in thick skin
    • waterproof
    • "clear"
    • thin keratinocyte layer (extra layer in THICK skin)
  13. context: 5 layers (strata) of keratinocytes in thick skin
    • disposable
    • 15-30 layers of dead keratinocytes
    • thicker layer in THICK skin
    • strong, water resistant barrier
  14. context: 3 layers of the skin (technically 2)
    • 1.Gives structural strength. C.T. with many fibers, fibroblasts, macrophages. Some adipocytes and blood vessels.
    • 2.Contains nerves, blood vessels, hair follicles, smooth muscles, glands, and lymphatic vessels.
    • 3.Sensory functions: pain, itch, tickle, temperature, touch, pressure
  15. context: dermis
    2 layers of the dermis
    • 1. papillary layer - Superficial (outer) 1/5. Areolar with lots of elastic fibers. Dermal papillae, capillary beds. Fingerprints. Whorls of ridges. Touch receptors (Meissner’s), free nerve endings sensing pain
    • 2. reticular layer - Deep (inner) 4/5. Dense irregular C.T. Collagen and elastic fibers. Also see some
    • adipose, hair follicles, nerves, oil glands, ducts of sweat glands, heat sensors.
  16. Cleavage tension lines
    • Elastin and collagen fibers oriented in some directions more than in others
    • parallel cuts = faster healing
    • overstretching = stretch marks (striae)
  17. Dermal strength and elasticity
    • collagen: resistance to stretching
    • elastic: stretch and recoil (exceed and will damage dermis NOT epidermis due to pregnancy or weight gain)
    • sagging and wrinkles occur from permanent reduction in amount of elastin in dermis due to hormones, aging, and UV light. USE RETIN-A (TRETONIN) - vitamin A derivative to increase blood flow in dermis and repairs (look young!!!)
  18. Dermal sensory structures (2)
    • 1. Meissner's corpuscle - egg shape, detect light touch near the dermal papillae.
    • location: fingertips, palms, soles, eyelids, tip of tongue & genitalia
    • 2. Pacinian corpuscle - onion shape, detect pressure near deeper reticular and subcutaneous layer
    • location: joints, tendons, muscles, mammary glands, & external genitalia
  19. Hypodermis
    • INDISTINCT border to dermis
    • attaches skin to underlying structures
    • Consists of loose connective tissue with collagen and elastic fibers
    • Site of lipid storage and contains about one-half of body’s
    • fat. – this is where lipsuction occurs.
    • Functions as: Energy source, Insulation, Padding, Blood reservoir (can hold 5-8% volume) superficial part has large veins & arteries.) e.g. can shunt blood for temperature regulation
    • for needles and liposuction
  20. Skin color influenced by 2 pigments
    • 1. carotene -orange yellow pigment found in orange vegetables accumulating in epidermal cells and fatty tissues of dermis. converts to Vitamin A
    • 2. melanin -yellow brown or black pigment produced by melanocytes in stratum germinativum from amino acid TYROSINE ... package in melanosomes to send to keratinocytes by phagocytosis
  21. context: skin color
    Function of keratinocytes
    • protect skin from UV damage
    • same number in all races
    • Vitiligo = loss of melanocytes due to possible autoimmune disease DOES NOT describe albino individuals
  22. Vitamin D
    • production from UV exposure to get cholecalciferol --> liver --> kidneys turn it to calcitriol (active vitamin D)
    • Vitamin D increases BLOOD CALCIUM for bone homeostasis, bone formation, growth and repair, nerve and muscle function
    • RICKETS: insufficient vitamin D for children = abnormal bone development
    • eat supplements or diet of Vitamin D
  23. context: Accessory structures of skin (FINALLY!!!)
    • shaft, root, hair bulb
    • Hair growth: the hair bulb produces the hair in cycles with a growth stage and a resting stage
    • growth: cells added at BASE as hair elongates
    • rest: follicle shortens and holds hair in place when hair falls out, new hair begin (good cause i've been losing tons of hair ... boo! stress!)

    • Accessory structures of hair:
    • 1. arrector pili - involuntary smooth muscle, goosebumps
    • 2. sebaceous gland - lubricate hair and controls bacteria
  24. context: Accessory structures of skin
    glands (2)
    • 1. sebaceous - oil - in dermis. holocrine (lysis and secrete contents and die). secrete sebum: oily white substance rich in lipids (+ electrolytes + proteins). lubricate and protect epidermis. (lips, eyelids, and genitalia - areas of no hair!)
    • 2. sudoriferous - sweat - merocrine (eccrine) in palms and soles, etc. more and superficial compared to apocrine. sensible perspiration for 3 functions:
    • a) Cools skin surface (lowers body temp)
    • b) Excretes water and electrolytes
    • c) Flushes Microorganisms & (has a peptide w/antibiotic properties dermicidin) dilutes harmful chemicals from skin
    • apocrine (secrete with no loss of cytoplasm like merocrine)- ducts terminate into follicles in armpits and groin. bacteria comes = STANK, stinky odor
    • Ceruminous gland: MODIFIED merocrine sweat gland in the ear canal (+ sebum = earwax)
    • Mammary gland: MODIFIED apocrine sweat gland to produce milk (lactation and pregnancy)
  25. Affects of aging
    integument damage, infection, cancer and overheating, drying out (less function of glands), less vitamin D3 making.
  26. Dermatitis
    • inflammation of skin
    • mostly papillary layer
    • allergen, irritant, or unknown immune problem
    • TREATMENT: antibiotics or hydrocortisone (anti-histimines)
    • ** Eczema/Atopic dermatitis (up to 40% of all kids) - crusting in stratum corneum as "messy rash"
    • if dandruff (seborrheic dermatitis) - use head and shoulders (zinc pyrithione), Selsun blue (Selenium
    • sulphide), Nizoral (Ketoconazole)
    • if contact dermatitis (irritant) - use Tacrolimus (inhibit T cells), corticosteroids (inhibit prostaglandins from inflammation), antihistimines (to stop itching)
  27. Psoriasis
    • silvery scales with stem cells in stratum germinativum active and dividing abnormally frequently (1.5 days vs normal 20 days).
    • ~5% in U.S. and ~2% worldwide affected
    • 20-30% genetic disposition

    • Dermatits Psoriasis : inflammation due to high proliferation (due to T cells go to epidermis and release cytokines)
    • TREATMENT: METHOTREXATE : inhibits proliferation of keratinocytes
    • immune suppressing medications: antibodies --> 1) Efalizumab (Raptiva) to T Cells or to 2) Adalimumab (Humira): antibodies to TNF
    • use coal tar to increase light sensitvity like for phototherapy - to decrease keratinocytes proliferation
  28. skin cancer
    • MOST COMMON cancer in U.S.
    • 3 types:
    • 1. basal-cell - MOST COMMON, BUT least malignant. basal/germinativum
    • 2. squamous-cell - spinosum
    • 3. melanoma - the BAD body because metastasize! cancer of melanocytes in germinativum layer
  29. 4 ways to figure if you MELANOMA
    • ABCD
    • 1. Asymmetry - irregular, raised, oozy
    • 2. Border - indistinct, irregular
    • 3. Color - mottled. combination of red, brown, tan, pink, white, blue, black tones
    • 4. Diameter - greater than 1/4th inch (55 mm).
  30. UVA, UVB, Sunscreens
    • UVA - 320 nm - 400 nm
    • UVB - 290 nm - 320 nm
    • (both bad and can cause skin cancer)
    • Sunscreens: protect against SCC but not BCC. chemicals (Ex. PABA, zinc oxide, titanium dioxide) cause harmful free radicals.
Card Set
lecture: the integumentary system
ibhs: skacel 524 exam 1 (holy cow ... im doing this lecture last because it's uber long -.-' )