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INTEGUMENTARY SYSTEMHonors Anatomy & Physiology
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
LAYERS OF THE EPIDERMIS
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
KERATINOCYTES
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
LANGERHANS CELLS
arise in red bone marrow then migrate to epidermis
easily damaged by UV radiation function: immune response vs.
microbes that invade
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
ANATOMY OF A HAIR
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 GROWTH CYCLE
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
ANATOMY 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 evaporates
2. adjusting flow of blood in dermis vessels dilate when body too warm vessels constrict when body too cold
FUNCTIONS OF THE SKIN
2. Blood Reservoir skin carries ~ 8 – 10% of total blood
flow in resting adult
FUNCTIONS OF THE SKIN3. Protection keratin protects underlying tissues from microbes,
abrasion, heat, & chemicals lipids released retard evaporation of water from
skin surface guarding vs. dehydration & retard water from entering thru skin
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 SKIN
4. Cutaneous Sensations skin contains variety of nerve endings
& receptors touch pressure vibration tickle pain temperature
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
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
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
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
SCARS
fibrosis: process of scar formation 2 types raised scars1. hypertrophic scar
scar remains w/in boundaries of wound
2. keloid extends boundaries of wound site
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
RULE OF 9’S
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