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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 - PowerPoint PPT Presentation
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Integumentary System
Honors BiologyPower point for copying
Essential question• What are the ways skin protects the
body?
Integumentary system• functions:1. protecting the body2. helping to regulate body temperature3. allows you to sense stimuli in your
environment4. stores blood5. synthesis of vit. D6. excretion & absorption of materials
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:1. epidermis 2. dermis3. sub Q below dermis & not technically part
of skin: contains fat (insulation), & blood vessels, nerves that supply the skin
Epidermis • keratinzed stratified squamous
epithelium• 4 main cell types:1. keratinocytes2. melanocytes3. Langerhans cells4. Merkel cells
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
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
Merkel Cells• least numerous of epidermal cells
(>1%)• deep in epidermis• in contact with Merkel disc (tactile
disc)• together detect different aspects of
touch
Thin Skin• covers most of body• 4 layers:1. stratum basale2. stratum spinosum3. stratum granulosum4. stratum corneum
Thick Skin• found in areas where exposure to
friction is the greatest• “thick” because has 1 extra layer: – stratum lucidum (between stratgum
granulosa & a thicker stratum corneum)
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
Dermis • 2nd, deeper layer of skin• composed mostly of CT• 2 regions:1. papillary region2. reticular region
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)
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
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)
Basis of skin color• 3 pigments contribute:1. Melanin2. Hemoglobin (hgb)3. Carotene
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
hemoglobin• in RBCs rosy color to lighter
skinned individuals• blushing: due to increased blood flow
(autonomic nervous system at work)
Carotene • yellow-orange pigment• precursor of vit. A
albinism• inherited inability to produce melanin• most due to cell’s inability to produce
tyrosinase
vitiligo• partial or complete lack of
melanocytes from patches of skin produces irregular white spots
• ? Immune system malfunction?
Skin color as diagnostic clue• cyanotic: when blood not adequately
oxygenated mucous membranes, nail beds & skin appears bluish
Skin color as diagnostic clue
• jaundice: due to build up of bilirubin (yellow pigment) in skin, sclera; usually indicates liver disease
Skin color as diagnostic clue
• erythema: redness of skin caused by engorgement of capillaries due to: injury, infection, inflammation, allergic reaction
Skin color as diagnostic clue
• pallor: paleness of the skin, seen in shock & anemia
Accessory structures of the skin
• all develop from embryonic epidermis
• include:– Hair– Nails– Glands
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
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
Hair• composed of columns of dead,
keratinized cells bonded together by extracellular proteins
Anatomy of a hair• shaft: portion of hair that projects
from scalp• root: portion below scalp• follicle: surrounds root of hair• arector pili: smooth muscle extends
from side of hair follicle superficial dermis
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
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
Skin glands• exocrine glands ass’c with the skin:1. sebaceous glands2. sudoriferous glands– eccrine sweat glands– apocrine sweat glands
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
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
Sudoriferous glands• sweat glands• sweat onto skin surface or hair
follicles
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
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
Functions of a nail• help us grasp & manipulate small
objects• protect ends of digits• allows scratching
Parts of exterior of a nail
Parts of a nail• body: visible part• root: part buried• matrix: where cells divide to produce
growth
Functions of the skin (#7)1. Thermoregulation
– the homeostatic regulation of body temperature
– skin achieves this in 2 ways:1. sweating • evaporation of sweat requires nrg (body heat)
so body cools down as sweat evaporates2. adjusting flow of blood in dermis• vessels dilate when body too warm• vessels constrict when body too cold
Functions of the skin2. Blood Reservoir• skin carries ~ 8 – 10% of total blood
flow in resting adult
Functions of the skin3. 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
Functions of the skin4. Cutaneous Sensations• skin contains variety of nerve endings
& receptors – touch– pressure– vibration– tickle– pain– temperature
Functions of the skin5. 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
Functions of the skin6. 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
Functions of the skin7. 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
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
Epidermal wound healing• abrasion: portion of skin has been
scraped away• in response to injury: basal cells of nearby
uninjured skin break contact with bm, enlarge, & migrate across the wound– migration continues across wound until meet
cells advancing from other side of wound– contact inhibition: cells stop migrating when
touch another cell
Deep wound healing• when injury extends deeper than
epidermis repair process more complex & scars form
• healing occurs in 4 phases:1. Inflammatory phase2. Migratory phase3. Proliferative phase4. Scar formation
Inflammatory phase• blood clot forms– loosely unites edges of wound
• inflammation develops– vascular response• vasodilation & increased permeability of
vessels– cellular response• phagocytic WBCs (neutrophils),
macrophages• fibroblasts
Migratory phase• clot scab• epithelial cells migrate beneath scab
to bridge wound• fibroblasts begin secreting collagen &
glycoproteins scar• *tissue filling wound called
granulation tissue
Proliferative phase• extensive growth of epithelial cells
beneath scab & deposition of collagen in random patterns (fibroblasts)
• growth of blood vessels
Scar formation• aka maturation phase• scab falls off• epidermis restored• collagen fibers become more organized• fibroblasts disappear• blood vessels restored to normal• scar tissue less elastic, fewer blood
vessels, +/- accessory structures of skin
Scar formation• aka maturation phase• scab falls off• epidermis restored• collagen fibers become more organized• fibroblasts disappear• blood vessels restored to normal• scar tissue less elastic, fewer blood
vessels, +/- accessory structures of skin
burns• tissue damage caused by excessive
heat, electricity, radioactivity, or corrosive chemicals that denature proteins in skin cells
• destroy skin’s ability to maintain homeostasis
• graded by their severity: 1st & 2nd degree = partial thickness burns; 3rd degree = full thickness
1st degree burns• only epidermis is damaged• example: sunburn• symptoms:– localized redness, swelling, & pain
• tx: immediate flushing with cool water (lessens pain)
• healing: 3 – 6 days +/- peeling of skin• results: normal
2nd degree burn• epidermis & upper dermis damaged,
some skin function lost, ass’c structures not damaged
• symptoms:– same as 1st degree + blisters (epidermis
separates from dermis due to accumulation of tissue fluid)
• example: any burn with blisters
2nd degree burns• tx: if 2° infection: antibiotics• lasts: 3 – 4 wks with +/- scarring
• AVOID: WEAR SUNSCREEN!
3rd degree burns• destroys epidermis, dermis, & subQ• no initial edema or pain or sensations
(receptors destroyed)• most skin functions lost• as healing starts marked edema• regeneration: months, + scarring• tx: +/- skin grafting
Systemic effects of a burn• greater threat to life than burn itself• include:
1. large loss of water, plasma, plasma proteins• shock
2. bacterial infection3. reduced circulation of blood4. decreased urine production5. diminshed immune response
Major burns• used to estimate extent & severity of
burns• major burn considered a 3° burn that
covers > 10% of body or a 2° burn that covers > 25% of surface area of body or any 3° burn on face, hands, feet, or perineum
• if burn > 70% surface area > ½ patients die
Skin cancer
• 3 common forms:1. Basal cell carcinoma2. Squamous cell carcinoma3. Malignant melanoma
• 1 & 2 50% more common in males
Basal cell carcinoma• > 78% all skin cancers• arises in cells from stratum basale– Sun-exposed areas
• rarely metastasizes.
Squamous cell carcinoma• ~20% of all skin cancers• arise from squamous cells in
epidermis• variable tendency to metastasize
Malignant melanoma• arise from melanocytes• ~2% of all skin cancers• deadliest form of skin cancer– spreads rapidly, can die w/in months of dx
• ~1/50 Americans will develop in their lifetimes (was 1/500 in 1930’s)– increase partly due to hole in ozone layer
(more UV rads)–main reason: more people spend more
time in sun &/or tanning beds
Malignant melanoma• key to successful tx is early detection• early warning signs: ABCD• A: asymetrical lesion• B: borders are irregular• C: color is uneven; may have
multiple coloration • D:diameter: ordinary moles <0.25 in
(pencil eraser)
Development of the integumentary system