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skin

the body's largest organ in terms of surface area and weight

skin

would cover 1.5-2.0 square meters of surface area if flattened

skin

makes up about 15% of total body weight

skin

consists of a superficial epidermis and a deeper dermis; below this the hypodermis, which is a layer of connective tissue

thick skin

has five epidermal layers and covers the palms, soles, fingers, and toes with surface layer of dead cells and it lacks hair follicles

thin skin

has four thinner epidermal layers and covers all other parts of the body

dermatology

the study and treatment of the integument adn the appearance and/or condition of one's kin can provide diagnostic information regarding one's overall health

epidermis

consists of keratinized stratified squamous epithelium that is organized into several distinct strata

epidermis

contains no blood vessels, so its cells depend on diffusion of oxygen adn nutrients from blood vessels in underlying connective tissue

stratum basale

consists of a single layer of cuboidal or columnar cells that continuously undergo mitotic cell division to produce new skin cells

keratinocytes

are teh most abundant cells and are held together by desmosomes

keratinocytes

filled with tough, fibrous keratin that protects skin from heat microbes, chemicals

keratinocytes

help waterproof skin

melanocytes

synthesize the pigment melanin

melanin

is responsisble for skin color and it absorbs ultraviolet radiation to protect from damaging effects of sunlight

merkel cells

are touch receptors that join with sensory neurons to form merkel discs

stratum spinosum

consists of several layers of keratinocytes

stratum spinosum

when skin is prepared for microscope slides, keratinocytes shrink and pull apart, except where attached by desosomes, giving this layer "spiny" appearance

dedritic (langerhans) cells

are macrophages that protect the body

dendritic (langerhans) cells

arise in bone marrow and migrate to epidermis to protect against microbes that invade skin

stratum granulosum

consists of keratinocytes that contain dark-staining granules of protein that eventually become keratin

keratinocytes

die and release waterproofing glycolipids that form a barrier between the stratum spinosum and the stratum granulosum

stratum lucidum

a thin, translucent layer of dead cells found only in thick skin

stratum corneum

contains up to 30 layers of dead, scaly keratinized cells and makes up about 75% of the thickness of the epidermis

dander

it takes 30-40 days for a keratinocyte to migrate to the skin's surface and exfoliate as . . . . .

dander

mots household dist is made up of this when it doesn't get eliminated

dander

presence of this in bedding provides food for dust mites

thickened callus

persisten friction with the stratum corneum can cause this to occur

feces of dust mites

allergy to household dust is actually allergy to . . . . .

dermis

consists of connective tissue comrpised mainly of collagen fibers, but elastic fibers, reticular fibers, fibroblasts, and macrophages are also present

dermal papillae

boundary between dermis and epidermis

finger-like projections

extend into the epidermis to form epidermal ridges on palsm, fingers, soles, toes, that increase grip by increasing friction

secretions

. . . . at these surfaces form fingerprints or footprints on objects

superficial zone

papillary layer

superficial zone

comprised of areolar connective tissue that contains elastic fibers

superficial zone

contains capillaries, touch receptors (Meissner's corpuscles), adn free nerve endings

deeper zone

reticular layer

deeper zone

comprised of dense irregular connective tissue that c ontains collagen bundles

deeper zoen

contains adipocytes, hair follicles, nerves, oil glands, and the ducts of sweat glands

subcutaneous layer

beneath the dermis is the subcutaneous hypodermis or superficial fascia

subcutaneous layer

consits of areolar tissue adn adipose tissue

subcutaneous layer

binds skin to underlying tissue, cushions body, provides thermal insulation, stores energy

subcutaneous layer

numerous blood vessels supply skin with oxygen adn nutrients and provide pathway for rapid absorption of drugs and/or mediciines into bloodstream

subcutaneous layer

contains nerve endings (pacinian corpuscles); sensitive to pressure

skin color

determined by genes that control interactiosn among melanin and carotene and hemoglobin

melanin

produces variations in skin color that range from pale yellow to black

ultraviolet radiation (sunlight)

stimulates melanocytes to increase their production of melanin, so the skin becomes darker

melanin

tends to be plentiful in face, limbs, around nipples, external genitalia

dark skin

melanin breaks down slowly making it visible in all epidermal layers

light skin

melanin breaks down rapidly making it less visible beyond stratum basale

freckles

flat patches of skin where melanin accumulates

moles

elevated patches of skin where melanin accumulates

vitiligo

results from partial or complete loss of melanocytes in patches of skin and produces irregular whtie blotches

carotene

is a yellow-orange pigment that accumulates in the stratum corneum or sub-cutaneous fat,which gives the skin a yellowish tint

translucent

results when melanin and carotene are in short supply, epidermis is . . . . .

hemoglobin

molecules in the blood become visible, producing pinkish flesh tones typical of caucasian skin

erythema

describes abnormal redness due to the dilation of dermal blood vessels during strenuous exercise or heat or anger of embarrasment

cyanosis

describes blueness of the skin due to insufficient oxygen in the blood because of airway obstructions or lung disease or cold weather

jaundice

a yellowing of the skin and whties of the eyes due to elevated levels of bilirubin in the blood, which is unable to be disposed fo by the liver

pallor

describes pale skin due to reduces dermal blood flow because of low blood pressure or shock of anemia or emotional stress

albinism

is a genetic defect that restults in a lack of teh amino acid tyrosine, which blocks the synthesis of melanin and produces pale skin, white hair, and pink eyes

hematoma

is a visible blood clot caused by trauma to the skin, which produces a bruise

hemangiomas

are "birthmarks" caused by benign tumors of dermal blood vessels

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