chapter 5 the integumentary system

epidermis

the superficial region of the skin, avascular, contains keratinocytes, melanocytes, dendritic cells, and tactile (merkel) cells

dermis

mostly connective tissue, vascular

keratinocytes

produce keratin (what makes skin waterproof), connected tightly by desmosomes, which is why skin comes off in layers

melanocytes

produce melanin which is packed into melanosomes. we all have the same amt of these, just diff amts of melanin produced, melanosomes are transferred to keratinocytes to protect nucleus from uv

dendritic cells

macrophages in deep epidermis

merkel cells

aka tactile cells, sensory neurons

stratum basale

first layer of skin

firmly attached to dermis

single cell layer

aka stratum germinativum

2nd layer of skin

stratum spinosum

several cell layers thick

weblike system of intermediate prekeratin filaments

keratinocytex appear spikey so called prickle cells

stratum granulosum

3rd layer of skin

thin layer of flattened cells

cells above this layer die (too far from blood supply dermal capillaries)

cells accumulate lamellar granules, a water-resistant glycolipids to slow water loss

statum lucidum

only in thick skin (palms of hands and soles of feet)

4th layer

translucentr keratinocytes so called the clear layer

very strong so adds protection

stratum corneum

outer layer of skin

papillary dermis

superficial layer of areolar connective

allows phagocytes to patrol for microorganisms

dermal papillae

fingerlike projections into epidermis (stratum basale)

projections contain capillary loops, free nerve endings, and touch receptors (meissners corpuscles)

dermal ridges

give rise ro epidermal ridges (ie fingerprints)

friction ridges

sweat pores in fingerprints leave the unique fingerprint pattern

reticular dermis

~80% of dermal thickness

lots of dense fibrous connective tissue

lots of elastic fibers to provide stretch recoil properties

collagen fibers provide strength

ECM contains pockets of adipose cells

cutaneous plexus

network of blood vessels between reticular layer and hypodermis (fat below the skin)

cleavage (tension) lines

caused by collagen fibers running parallel to skin surface

externally invisible

incisions parallel heal better, so surgeons follow the lines

wrinkles follow these lines

flexure lines

dermal folds at or near joints

dermis is closely attached to deeper structures

skins inability to slide causes deep creases

striae

aka stretch marks

lines of cleavage have stretched causing dermal tears

silvery white scars

skin colour

affected by

• melanin

  • made from tyrosine

• carotene

  • accumulates in stratum corneum and hypodermis

• hemoglobin

cyanosis

blue tint to skin, low oxgenation of hemoglobin

pallor

blanching or pale colour

anemia, low BP

erythema

redness

fever, hypertension (high BP), inflammation, allergy

jaundice

yellow cast

issue w biliruben, liver disorders

ecchymoses

or hematomas, bruises

clotted blood beneath skin

hair functions

protect from heat loss

sheild skin from sunlight

hair on head cushions to gaurd physical trauma

warn of insects of skin

• more sensory nerve edings near the base of a hair follicle, so we feel it if a bug brushes the hair

hair

flexible strands of dead keratinized cells, keratin is harder, shaft (keratinization is complete) and root(keratinization is still happening)

medulla

central core of hair strand

this part must be coloured so we use bleach to reach it

cortex

middle part of a hair strand, several layers of flattened cells surroundingf the medulla

cuticle of hair

outermost layer of hair, overlapping layers of single cells

red hair

contains an extra pigment, pheomelanin

peripheral connective tissue sheath

derived from dermis

aka fibrous sheath

glassy membrane

thickened basal lamina

epithelial root sheath

derived from epidermis

hair matrix

inner part of bulb thats actively dividing

arrector pili

small band of smooth muscle attached to follicle

hair papilla

dermal tissue containing a knot of capillaries that supplies nutrients to growing hair

vellus hair

pale fine body hair of children and women

terminal hair

coarse long hair

head, eyebrows, pubes, armpit, facial hair

hirsutism

excess facial hair in women due to pcos (polycystic ovary syndrome)

alopecia

hair thinning

male pattern baldness

follicular response to DHT (dihydrotestosterone)

nail bed

epidermis underneath keratinized nail plate

nail matrix

thickened part of bed responsible for nail growth

eponychium

aka cuticle, important keeps pathogens out

hyponychium

area under free edge of nail that accumulates dirt

lunule

thickened nail matrix, half moon at bottom of nail, appears white diff colour can indicate disease

koilonchya

spoon nail, concave nail can indicate iron deficiency

sudoriferous glands

exocrine sweat glands

eccrine and apocrine sweat glands

eccrine (merocrine) sweat glands

thermoregulation by releasing sweat, controlled by sympathetic nervous system

apocrine sweat glands

genital and armpit sweat, have BO, begin functioning at puberty

other modified apocrine glands

mammary glands, ceruminous glands (lining of ear canal secretes cerumen which is earwax)

sebaceous (oil) glands

most develop from hair follicles and secrete into hair follicles, secrete sebum (oily holocrine secretion)

seborrhea

aka cradle cap, overactive sebaceous glands in infants

chemical barrier

cells secrete defensin, and sebum which lower skin pH defending against bacterial multiplication

melanin provides chemical barrier against uv radiation

insensible perspiration

normal resting body temprature produces unnoticeable sweat

sensible perspiration

increase in noticble sweat to cool body

basal cell carcinoma

Does not metastasize, least malignant and most common

stratum basale cells invade dermis and hypodermis

kinda poking in, goes into papillary layer

commonly appears in high sun areas (ex nose)

squamous cell carcinoma

second most common type

keratinocytes of stratum spinosum (second layer of skin)

scaly reddened papule on (commonly) scalp, ears, lower lip, and hands

melanoma

cancer of melanocytes, most dangerous due to being highly metastatic (and resistant to chemotherapy)

ABCD RULE

• A: asymmetry (the two sides of pigmentation dont match)

• B: border irregularity

• C: colour (several)

• D: diameter (larger than 6 mm)

rule of nines

to evalute burns, boy is broken down into 11 sections, with each section representing 9%

estimate volume of fluid loss and hm fluid to give

critical burns

> 25% of the body has second degree burns

>10% has third degree

Face hands or feet have third degree burns

burn treatment

Debridement (removal of the burned skin)

antibiotics

temporary covering (artificial skin)

skin grafts