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40 Cards in this Set
- Front
- Back
Epidermis
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superficial region
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Dermis
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middle region |
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Hypodermis (superficial fascia)
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deepest region |
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Keratinocytes
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•produce fibrous protein keratin |
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Melanocytes |
* 10–25% of cells in lower epidermis * Produce pigment melanin |
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Epidermal dendritic (Langerhans) cells
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macrophages that help activate immune system
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Tactile(Merkel) cells
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•touch receptors
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Stratum corneum |
Most superficial layer; 20–30 layers of dead cells represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space. |
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Stratum granulosum |
Three to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules. |
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Stratum spinosum |
Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin. |
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Stratum basale |
Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. See occasional melanocytes and epidermal dendritic cells. |
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Layers of the Epidermis: Stratum Spinosum(Prickly Layer)
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•Cells contain a weblike system of intermediate prekeratin filaments attached to desmosomes
•Abundant melanin granules and dendritic cells |
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Dermis |
•Strong, flexible connective tissue •Cells include fibro-blasts, macrophages, and occasionally mast cells and white blood cells •Two layers: •Papillary •Reticular |
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Papillary layer
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•Areolar connective tissue with collagen and elastic fibers and blood vessels
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•Reticular layer
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•~80% of the thickness of dermis •Collagen fibers provide strength and resiliency •Elastic fibers provide stretch-recoil properties |
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1.Melanin
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•Yellow to reddish-brown to black, responsible for dark skin colors
•Produced in melanocytes; migrates to keratinocytes where it forms “pigment shields” for nuclei
•Frecklesand pigmented moles •Local accumulations of melanin |
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2.Carotene
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•Yellow to orange, most obvious in the palms and soles
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3.Hemoglobin
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•Responsible for the pinkish hue of skin
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1.Eccrine(merocrine) sweat glands—abundant on palms, soles, and forehead
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•Sweat: 99% water, NaCl, vitamin C, antibodies, dermcidin, metabolic wastes
•Ducts connect to pores •Function in thermoregulation |
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2.Apocrine sweat glands—confined toaxillary and anogenitalareas
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•Sebum: sweat + fatty substances and proteins
•Ducts connect to hair follicles •Functional from puberty onward (as sexual scent glands?) |
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•Specializedapocrine glands
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•Ceruminousglands—in external ear canal; secrete cerumen
•Mammaryglands |
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Sebaceous (Oil) Glands
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•Widelydistributed
•Mostdevelop from hair follicles •Becomeactive at puberty •Sebum •Oilyholocrine secretion •Bactericidal •Softenshair and skin |
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•Arrectorpili
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•Smoothmuscle attached to follicle
•Responsiblefor “goose bumps” |
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Vellus
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pale, fine body hair of children and adult females
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Terminal
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•coarse, long hair of eyebrows, scalp, axillary, and pubic regions (and face and neck of males) |
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1.Protection—three types of barriers |
•Chemical •Low pH secretions (acid mantle) and defensins retard bacterial activity |
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•Physical/ mechanical barriers |
•Keratin and glycolipids block most waterand water- soluble substances •Limited penetration of skin bylipid-soluble substances, plant oleoresins (e.g., poison ivy), organicsolvents, salts of heavy metals, some drugs |
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•Biological barriers |
•Dendritic cells, macrophages, and DNA |
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2.Body temperature regulation |
•~500ml/day of routine insensible perspiration (at normal body temperature)
•Atelevated temperature, dilation of dermal vessels and increased sweat glandactivity (sensible perspirations) cool the body |
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3.Cutaneous sensations |
•Temperature,touch, and pain
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4.Metabolic functions |
•Synthesisof vitamin D precursor and collagenase
•Chemicalconversion of carcinogens and some hormones |
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Blood reservoir
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5.up to 5% of body’s blood volume |
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Excretion
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6.nitrogenous wastes and salt in sweat
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•Basalcell carcinoma |
•Least malignant, most common |
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•Squamouscell carcinoma |
Secondmost common
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•Melanoma |
•Most dangerous |
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Ectoderm
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•epidermis |
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Mesoderm
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•dermisand hypodermis
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Lanugo coat:
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•covering of delicate hairs in 5th and 6th month
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Vernixcaseosa
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•sebaceousgland secretion; protects skin of fetus
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