skin Flashcards
epidermal wound healing process
- abrasion or minor burn
- basal cells migrate across the wound
- contact inhibition w/ other cells then stops migration
- epidermal growth factor stimulates cell division
- full thickness of epidermis results from further cell division
deep wound healing process
4 phases if reaches dermis
1) inflammatory phase
2) migratory phase
3) proliferative phase
4) maturation phase
inflammatory phase
clots unite wound edges and white blood cells arrive from dilated and more permeable blood vessels
migratory phase
regrowth of epithelial cells & formation of scar tissue thru fibroblasts
proliferative phase
completion of tissue formation from fibroblasts
maturation phase
scab falls off
first degree burn
only in epidermis (sunburn)
second degree burn
destroys epidermis and part of dermis
- fluid filled blisters separate epidermis and dermis
- epidermal derivatives are not damaged
- heals w/o grafting in 3-4 weeks but may scar
third degree burn
full thickness burn
- destroys epidermis, dermis, and epidermal derivatives
- damaged area is numb due to loss of sensory nerves
skin grafts
used when new skin cannot regenerate (stratum basale & stem cells are destroyed)
skin graft is covering of wound with piece of healthy skin
common place: buttocks, thigh
autologous skin
transportation of patients skin grown in culture
isograft
skin graft from twin
autograph
skin graft from self
rules of 9
way to determine extent of burns
- body is divided into 11 areas each representing 9% of total body surface area
problems of rules of 9
- shock due to water, plasma, and plasma protein
- circulatory & kidney problem from loss of plasma
- bacterial infection
photodamage
ultraviolet lights (UVA & UVB) both damage the skin
- acute overexposure causes sunburn
- DNA damage can lead to skin cancer
UVA
- longer wavelengths that penetrate deep into skin (layers under skin)
- leads to skin inflammation and skin cancer
- produces oxygen free radicals that damage collagen and elastic fibers (wrinkling in skin)
UVB
- shorter UVB waves cause skin to burn
- driver of skin ell mutations that cause skin cancer
skin cancer
1 million cases a year
3 most common types of skin cancer
basal cell carcinoma (rarely metastasize)
squamous cell carcinoma (may metastasize)
malignant melanomas (metastasize rapidly)
malignant melanomas
- most common cancer in young women
- arise from melanocytes (life threatening)
- key for treatment is ABCDE
risk factors: skin color, sun exposure, family history, age, & immunological status
stages of melanoma
0: melanoma confined to epidermal region of skin
1: localized disease, only in skin & v/ thin
2: localized disease, thicker than stage 1
3: spreads to lymph nodes
4: spreads to other organs
ABCDE
a (symmetry)
b (orders): uneven, jagged borders
c (colors): more than 1 color
d (iameter): larger than pencil eraser (1/4 in)
e (volving):suddenly changing in size, shape, color, etc
shaft
- visible
- medulla, cortex, cuticle
- hs round in straight hair
- hs oval in wavy hair
follicle
- surronds root
- external root sheathe
- internal root sheathe
-base of follicle is bulb: blood vessels, germinal cell layer
root
below the surface
arrector pili
- smooth muscle in dermis contracts w/ cold or fear
- forms goosebumps as hair is pulled vertically
hair root plexus
detects hair movement
sebaceous (oil) glands
secretary portion in the dermis (most open into hair shafts)
- sebum
- acne
sebum
- combination of cholesterol, proteins, fat, & salts
- keeps hair and skin soft and pliable
- inhibits growth of bacteria & fungi (ringworm)
acne
- bacterial inflammation of glands
- secretions stimulated by hormones at puberty
- antibiotics kill bacteria trapped in skin pores
eccrine sweat glands
duct to surface
- most areas of skin
- secretory portion in dermis w/ duct to surface
- regulate body temperature w/ perspiration
apocrine sweat gland
duct to dermis hair follicle
- armpit and pubic region
- secretions more viscous (“milky”)
cells in epidermis
- keratinocytes
- melanocytes
- langerhan cells
- merkel cells
- fibroblast cells
keratinocytes
- 90%
- produce keratin
- a fibrous protein protecting skin & tissue
melanocytes
- 8%
- produces melanin pigment
- melanin transferred to other cells w/long cell process
- absorb uv rays and determines skin color
langerhan cells
from bone marrow, provides immunity
merkel cells
deepest layer, form light touch receptor w/ sensory neuron
fibroblast cells
produce fibrous protein called collagen
general function of skins
- regulation of body temp
- protection as physical barrier
- sensory receptors
- exception and absorption
- synthesis of vitamin d from uv rays
regulation of body temp
thermoregulation
- perspiration and evaporation
- dusting blood flow to body surface
- shivering & constriction of blood vessels raises internal body temp
moderate exercise
more blood to surface to lower temp
extreme exercise
blood shunted to muscles, body temp rises
protection as physical barrier
- tight cell junctions prevent bacterial invasions
- lipids released hinder evaporation
- melanin & other pipgment protect against uv radiation
- langerham cells alert immune system
sensory receptors
> touch - meissner’s corpuscle
temperature (change) - termoreceptro
pressure - pacinian corpuscle
vibration - merkel cells
tickling & some pain sensations - nociceptor
excretion
- only a minor role played by skin
- 400 mL evaporates daily
- small amounts salt, co2, ammonia, & urea excreted
absorption
- lipid soluble substances cane absorbed thru skin
- vitamin A,D,E,K, & oxygen and CO2
- acetone, & dry cleaning fluid, etc
synthesis of vitamin d
- sunlight activates precursor to vitamin d
- enzymes in liver & kidney transform molecule into calcitriol (most active form of vitamin d)
- necessary vitamin for absorption of calcium from food in the gastrointestinal tract
carotene
@ dermis
- yellow-orange pigment (precursor of vitamin A)
- stratum corneum and dermis
hemoglobin
- red, oxygen carrying pigment in blood cells
- if other pigment not present epidermis is translucent (pinkness evident)`
age related structural changes
- collagen fibers decrease
- elastic fibers less elastic
- fibroblasts decrease in number
- oil glands shrink and skin becomes dry
- wall of blood vessels in dermis thicken, decreasing nutrient availability. this leads to thinner skin as subcutaneous fat is lost
