CH 5 Flashcards
(31 cards)
What are the two distinct regions of skin?
- epidermis– epithelium; avascular
- dermis–underlies the epidermis. Connective tissue; vascular.
What is the hypodermis? is it considered apart of the skin?
it is superficial fascia. subcutaneous layer. not apart of the skin. adipose tissue; anchors skin
What is the epidermis composed of?
keratinized stratified squamous epithelium
List and describe each cell found in the epidermis
- keratinocytes: keratin, most epidermal cells are keratinocytes, tied together by desmosomes
- melanocytes: deep epidermis, pigment clusters packaged in melanosomes
- dendritic (Langerhans) cells: macrophages, immune system.
- Tactile (merkel) cells: sensory receptors; touch
Identify and describe the layers of the epidermis
- stratum basale (deepest epidermal layer): attached to the dermis. crazy amount of mitosis. also known as stratum germinativum. 10-25% are melanocytes.
- Stratum spinosum (prickly layer): several layers thick. keratinocytes appear spick (prickle cells)
- Stratum granulosum (granular layer): four to six cells thick. thin layer: flat cells. Cell appearance starts to change. Nuclei and organelles disintegrate. keratinization begins.
- Stratum lucidum (only in thick skin) (clear layer): two-three rows of clear, flat, dead keratinocytes. superficial to stratum granulosum.
- Stratum Corneum (horny layer): 20-30 rows of flat, anucleated, keratinized dead cells. 3/4 of epidermal thickness.
What are the characteristics of the dermis?
strong flexible connective tissue; contains fibroblasts, macrophages, mast cells, and white blood cells. also contains nerves, blood vessels, lymphatic vessels, epidermal hair follicles, oil glands, and sweat glands.
Name and describe the two dermal layers
- papillary: the superficial layer of areolar connective tissue. Dermal papillae: fingerlike projection into the epidermis (in thick skin, dermal papillae give rise to epidermal ridge resulting in friction ridges, gripping, sense of touch resulting in fingerprint patterns)
- reticular: about 80% of the dermal thickness. coarse, dense fibrous connective tissue.
-cutaneous plexus: network of blood vessels between reticular layer and hypodermis.
-extracellular matrix: pockets of adipocytes
-Cleavage (tension) line in reticular layer caused by many collagen fibers running parallel to skin surface. Externally invisible. incision.
-flexure line of the reticular layer is a dermal fold at our near joints.
Name the three pigments that contribute to skin color
- melanin: made in skin by melanocytes. amino acid tyrosine. melanosomes. Skin color differences are because of varying amounts and forms of melanin. Freckles and moles are local accumulations of melanin.
- Carotene: yellow-orange pigment; diet. most obvious in palms and soles. accumulates in stratum corneum and hypodermis. Can be converted to vitamin A and epidermal health.
- hemoglobin: pinkish hue of fair skin. the skin of Caucasians is most transparent, so the color of hemoglobin shows through.
Define cyanosis
blue skin color; low oxygenated of hemoglobin
define erythema
redness. fever, hypertension, infammatory, allergy.
Define jaundice
yellow cast. liver disorders.
define bruises
black and blue marks. also called ecchymoses or hematomas. clotted blood beneath the skin. color of bruise changes as clot breaks down
What is hair made of? what are the functions of hair?
Flexible strands of the dead, keratinized cells. produced by hair follicles. Contains hard keratin, not like soft keratin found in skin.
Functions include:
-warn of insects on skin
-hair on head-physical trauma
-protect from heat loss
-shield skin from sunlight.
What is the shaft and root of hair?
Shaft: the area above scalp; keratinization is complete.
root: area within scalp; keratinization still occuring.
What are the three parts of hair shaft?
- medulla: central core of large cells and air spaces
- cortex: several layers of flattened cells surrounding medulla
- cuticle: outer layer consisting of overlapping layer of single cells
What results in hair color?
hair pigments are made by melanocytes in hair follicles
-combinations of different melanines (yellow, rust, brown, black) create all the hair colors. Red hair has additional pheomelanin pigment. Grey/white hair-melanin production decreases; air bubbles replace melanin in shaft.
what are the structure of a hair follicle?
- Hair bulb: expanded area at deep end of follicle
- hair follicle receptor (root hair plexus): sensory nerve endings wrapped around bulb. hair is a sensory touch receptor.
- Follicle wall: composed of:
-peripheral connective tissue sheath (fibrous sheath) (derived from dermis)- glassy membrane: thickened basal lamina.
- epithelial root sheath: derived from epidermis.
- hair matrix: area at the bottom of bulb. active area of bulb; produces hair cells. as new cells are made, older ones pushed upward.
- arrector pili: small band of smooth muscle attached to follicle. “goosebumbs”
- hair papilla: dermal tissue containing a ton of capillaries that supplies nutrients to growing hair.
What is the difference from vellus and terminal hair?
Vellus hair: pale fine body hair of children and adult females
Terminal hair: coarse long hair
-scalp, eyebrows.
-at puberty: axillary and pubic regions
What are nails and what are their purose?
scale-like modification of epidermis; contains hard keratin. to protect.
identify and describe structure of the nail
- protective cover: distal, dorsal surface of fingers and toes
-free edge, nail plate and root - nail bed– under the keratinized nail plate
- nail matrix- thickened portion of nail bed responsible for nail growth.
- nail fold: lateral skin folds overlapping nail border
- epinychium- bottom nail folds also called cuticle
- hyponychium- are under free edge of nail plate that accumulates dirt
- lunule (lunula): half moon shaped area at bottom, most active growing region of the nail.
What are the two main types of sweat glands
- eccrine (merocrine) sweat glands: most numerous type. abundant on plams, soles and forehead. ducts connect to pores. functions in thermoregulation. (sympathetic nervous system). Their secretion is swat (99% of water, salt, vitamin C, antibodies, dermcidin and metabolic waste)
- apocrine sweat glands: axillary and anogenital area. secretions are a fatty substance and proteins. (bacteria break down sweat–> body odor). Larger than eccrine sweat glands; ducts empty into hair follicles. Begins functioning at puberty.
What are ceruminous and mammary glands?
Ceruminous glands: lining od external ear canal; secret cerumen (earwax)
mammary glands: secrete milk
Describe the characteristics of sebaceous (oil) glands
widely distributed, except for palms and soles. most develop from hair follicles; secrete into hair follicles. relatively inactive until puberty.
-secrete sebum: oily holocrine secretion, bactericidal properties. softens and waterproof hair and skin.
What are the functions of skin?
- protection
- body temperature
- cutaneous sensations
- metabolic functions
- blood reservoir
- excretion of wastes
