Lecture 7 Information - Ch 5 Skin (Dermis)

Thin Skin

hairy, less adipose/CT, more elastic, pigment, 4 epidermal layers, rest of body

Thick Skin

hairless (no hair follicles), dense adipose/CT, less elastic (fiber), less pigment, high conc. of sweat pores (high degree of openings), 5 epidermal layers, palms and soles of feet

Dermis

strong flexible CT, fibroblasts: produce fiber CT, macrophages, mast cells: manufacture histamine that mediates immune response, WBC: help control bacterial invaders past epidermis, nerves, blood vessels, lymphatic vessels, hair follicles, oil and sweat glands, two layers: papillary (20%) and reticular (80%)

Layers of the Dermis: Papillary Layer

20% of thickness, thin, superficial, loose areolar CT w/ collagen and elastic fibers, loosely woven, heavily vascularized, superior surface contains dermal papillae: capillary loops, Meissner’s corpuscles (rapidly adapting touch senses), free nerve endings

Dermal Modifications

friction ridges (finger prints), dermal papillae sticks up and epidermal ridges stick down

Layers of the Dermis: Reticular Layer

80% of thickness, dense irregular CT, large collagen (adds strength and resiliency to skin) fibers that go in different directions to allow resistance of tension mimicking muscle fiber structure, elastic fibers provide stretch-recoil properties, cutaneous plexus: network of blood vessels that lie between reticular and hypodermis, cleavage (tension) lines (Langer’s lines): longitudinally in head/limbs and circular around neck/trunk, externally invisible, important guide lines in surgery to decreases tension across wound where incision parallel to underlying muscle fibers (easier to close, less scarring, faster healing), flexure lines: dermal folds at/near joints where dermis attaches tightly to deeper structures (wrists, fingers, palms, soles, toes), striae: “stretch marks,” tears due to stretching in dermis from quick change in size, ex: pregnancy, weight loss, weight gain, blister: accumulation of inflammatory fluid, separate dermis and epidermis, heal on its own or popped may scar

Skin Color

3 pigments contribute: melanin, carotene, hemoglobin

Skin Color: Melanin

only pigment made in skin (melanocytes), reddish yellow (pheomelanin) to brownish black (eumelanin), differences from type of melanin, amount synthesized, and how long retained by keratinocytes (not #), affects skin, hair, and eye color, melanocytes stimulated to greater activity w/ increased sun exposure, freckles and pigmented moles are local accumulations of melanin

Skin Color: Carotene

exogenous through diet, yellow orange pigment found in plants, accumulates in stratum corneum and fatty tissue of hypodermis, most obvious in thick skin (palms and soles)

Skin Color: Hemoglobin

function by binding and transporting O2, pinkish hue of fair skin = lower levels of melanin, epidermis is nearly transparent: reflects Hb in blood of dermal capillaries

Skin Color: Stimuli

alterations in skin color can indicate disease/emotional stimuli, ex: cyanosis, erythema, pallor, jaundice, bronzing, bruises

Skin Color: Cyanosis

blue, low oxygenation of hemoglobin (respiratory/cardiac), poor circulation, present in mucous membrane/nail beds

Skin Color: Erythema

redness, fever (high temp.), hypertension (high BP), inflammation (typically localized), allergy (typically localized), embarrassment (flushing from emotion)

Skin Color: Palor

blanching or pale color, anemia, low BP, fear, anger

Skin Color: Jaundice

yellow cast, liver or gallbladder disorders, bile accumulation

Skin Color: Bronzing

metallic, inadequate steroid hormones, endocrine disorders, ex: Addison’s disease

Skin Color: Bruises

black and blue marks, clotted blood beneath skin, hematomas, bleeds into subcutaneous tissue

Burns

one of greatest dangers to integumentary system; ex: sun, fire, electrical, chemical, hot surfaces; 3 major classes: first, second, and third degree

Burns: 1st Degree

“superficial burn;” pain, redness, swelling; dry; symptomatic treatment, heals by itself; repetition can lead to cancer; affects epidermis

Burns: 2nd Degree

“superficial partial thickness” or “deep partial thickness burns;” redness, pain, blistering (epidermis and dermis will separate for fluid buildup), scarring, infection; moist; symptomatic treatment, leave blisters to heal and resorb itself; affects epidermis and dermis

Burns: 3rd Degree

“full thickness burns;” very damaging, infection, painless bc all nerves destroyed; stiff, dry, leathery; treatment requires grafting/surgical intervention; affects epidermis, dermis, and hypodermis

Burns: 4th Degree

additional classification; charred, dead tissue, painless bc all nerves destroyed; amputation, functional impairment, death; affects epidermis, dermis, hypodermis, muscle, and bone

Burns: Rule of Nine

estimation of burn damage; >20-25% require IV fluid resuscitation, >30-40% may be fatal w/o tx; anterior/posterior head/neck = 9%, anterior/posterior upper extremities = 18%, anterior/posterior trunk = 36%, perineum = 1%, anterior/posterior lower extremities = 36%

Accessory Structures of the Skin: Derivatives of the Epidermis

sudoriferous glands, sebaceous glands, hair and hair follicles, nails

Sudoriferous Glands (Sweat Glands)

found over entire surface of body; prevent overheating of body; secrete sweat; specialized to secrete cerumen (wax) or milk, ceruminous glands in external ear canal and lacteriferous (mammary) glands in the breasts, 2 types: eccrine (merocine) and apocrine (apocrine)