integumentary system

function

protective covering, body temperature regulation, slows water loss from deeper tissues, sensory receptors, synthesis of biochemicals, excretes waste

epidermis

outer layer, stratified squamous epithelium (keratin), protects underlying tissue from water loss, injury, chemicals, pathogens), balanced cell division and death ratio

dermis

thicker inner layer, made of connective tissue, smooth muscle, nervous tissue, blood. binds epidermis to underlying tissues, skin elasticity, has blood vessels that nourish skin cells and regulate body temperature. sensory and motor nerve cells scattered. 2 zones- papillary (small blood vessels for diffusion and sensory receptors), reticular (deep and dense, collagan, hair follicle, gland, blood vessels, muscles)

basement membrane

anchors epidermis to dermis

subcutaneous layer

beneath dermis, not a layer of skin, adipose and areolar tissue (loose connective)

melanin

pigment, skin color, produced by melanocytes in deep part of epidermis, absorbs UV radiation to prevent DNA damange in skin cells. made only in melanocytes but can be present in neighboring cells-when melanin graunules which absorb the UV reach keratinized cells they break apart and cause pigmentation

what determines skin color

amount of melanin produced and size and distribution of granules(all ppl have abt same # melanocytes). environmental and physiological factors- UV light, sunlight, X rays stimulate melanin production and darken melanin. oxygenation levels of blood in dermal vessels- good-pinkish tone, bad-bluish. diet rich in beta carotene- orange tone, biochemical imbalances

cutaneous carcinoma

squamous or basal cell carcinoma. originates in epithelial cells deep in epidermis, most common in ppl exposed to sunlight, develop from hard, dry, scaly lesions with reddish bases. slow growth- surgery and radiation. can be failed apoptosis 

cutaneous melanomas

melanocarcinomas or malignant melanomas. orginate in melanocytes, pigmented, often various colors, caused by short intermittent exposure to high intensity sunlight, horizontal growth followed by downward. hard to treat as it originated low in skin. ABCDE checklist= asymmetry, border, color, diameter, elevation

nails

protection. nail plate-covers, nail bed with specialized epithelial cells and continuous with skin epithelium, lunuela covers region of most active cell division- cells divide, become keratinized, get pushed out, and incorporate into nail plate

hair follicles

tube-like depression in skin, present over most of body, cells nourished by dermal blood vessels, cells at base of follicle divide and push older cells upward-as cells get farther from blood supply they keratinize and die=hair shaft. hair is composed of dead epiderman cells. erector pili is smooth muscle attached to hair that contracts so it can stand up

sebaceous glands

glandular tissue- exocrine and holocrine, associated with hair follicles, sebum-oily mix of fats and cell debris, secretes into hair follicles, keeps hair and skin soft, pliable, waterproof. overactive/inflamed glands cause acne(plugged sebaceous glands)

sweat glands

coil in deep dermis or superficial sutcutaneous layer, reach pore at skin surface- exocrine. deepest part of coil lined with sweat secreting epithelial cells. sweat=water, salt, waste. eccrine glands-most numerous, merocrine, respond to rise in body temp. apocrine glands- actually merocrine, activated at puberty-ducts open into hair follicles, odor when bacteria metabolize secretions, respond to distress, fear, pain, sexual arousal. specialized sweat glands- ceruminous-external ear canal, mammary

importance of body temperature regulation

a shift can distrupt the rate of metabolic reaction, homeostasis is a balance between heat lost and produced. skin plays a key role in homeostatic mechanisms that regulate body temperature

what happens when body overheats

heat from muscles are released and carried away by the blood, reaching the hypothalamus and signaling the walls of dermal blood vessels to relax (vasodilate) so that more blood can flow and heat can escape from the skin. sweat is also released when nervous system actives eccrine glands-evaporation of sweat carries heat away from surface

what happens when body too cold

hypothalamus signals the walls of dermal blood vessels to contract (vasoconstriction), less blood flow, less heat loss from skin, sweat glands inactive. shivering can occur when continued drop in body temperature as nervous system stimulates skeletal muscles to contract triggering cellular respiration which generates heat- if that isnt enough muscles rhymically contract w/more force to generate more

methods of heat loss

radiation-infrared heat rays escape (primary). conduction- heat moves from skin to cooler objects. convection- heat loss into circulating air currents. evaporation-sweat changes into a gas and carries heat away

inflammation

response to injury or stress, blood vessels dialate and become permeable so fluids can leak into damaged tissues. dialated blood vessels provide nutrients and O2 to tissues to aid healing and WBCs to help clean up

signs of inflammation

redness=vasodilation causes blood to flow into the area. heat=blood accumulation and byproduct of increased metabolic activity. pain=injury to neurons and increased pressure from edema. swelling=increased permeability of blood vessels, fluid leaving the blood goes into tissue spaces

pros of transdermal drug delivery

convenient, pain free, can be self-administered, steady levels of drugs in system, avoids gastrointestinal degration and hepatic first-pass metabolism, lower amount of drug can be delivered, reduced side effects, cheaper and delivers drugs over 1-7 days

cons of transdermal drug delivery

effects skin barrier layer of stratum corneum using microneedles, thermal ablation, microdermabrasion, electroporation, cavitian ultrasound, skin irritation, not all drugs/compounds can be delivered this way (mainly small lipophilic low-dose drugs)