Honors Anatomy & Physiology. What are the ways skin protects the body?

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