introduction and epidermis
this membrane covers the outer surface of the body
largest organ in the body, 22 sq ft & 10-11 lbs
thinnest on eyelids
thickest on heels
0.5-4 mm thick
cutaneous membrane
skin
epidermis has 4 thin layers and 5 thick
-te bottom/deepest- continuous cell division
8-10 rows of keratinocytes
3-5 rows of keratinocytes- apoptosis & lamellar granules
4-6 rows of dead keratinocytes- thick skin only
outermost layer, up to 50 rows of flat cell remnants
dead keratinocytes
stratum basale/germinastrum
stratum spinosum
stratum granulosum
straum lucidum
stratum corneum
direction of collagen
formed by dermal paplillae
finger prints
increase firmness of grip by increasing friction
lines of cleavage
epidermal ridges
attaches skin to underlying tissue
adipose
blood vessels and nerves
lamellated corpuscles
hypdermis- subcutaneous layer
sweat gland
most numerous-secrete watery solution & thermoregulate
released in response to emotional stress- fear/embarassment
eccrine sweat gland
thermoregulates
sensory perception
vitemin d
emotional expression such as blushing
blood reservoir
SKIN
acummulation of waxy kertin
callus
dadruff
keratinization
connective tissye w collagen and elastic fibers
contains fibroblasts
2 regions: papillary and reticular
dermis
fast turn over
epidermis resists damage and offers protection
dermis provides temperature stability and prevents dehydratiion
subcutaneous insulates and stores fat and achors
benefits of skin
cells of haiir matric dividew
stop dividing and shrink
no growth then new groth
partial to full haur loss
growth stage
regression stage
resting stage
alopecia
keratinized stratified squamous epithelium
contains 4 cell types
epidermis
most of the body- hawds rmpit groin
palms plamar surface digits soles
thin skin
thick skin
recessivley inherited
complete or partial absense of pigment in skin hair and eyes
lack of melanin
albinism
pilli
dead keratinized epidermal cells
genetics determines thickness and distribution
functions include touch sensation, protects against sun, and heat loss
HAIR
shaft and root
innermost-absent in think ahir and dertmines color
middle- elongated cells
outermoswtt-keratinized
medulla
cortex
cuticle
dermis- Ct
hypodermis- underneath dermis
outer layer
inner layer
subcutaneous
contains eumelanin and pheomelanin
hemoglobin and carotine
melanin
chronic disorder that causes depigmentation patches of the skin
unknown cause
genetic
immune system dyfunction
vitiligo
differrent layers- superficial and deep
merkell discs, free nerve endings, meisser corpuscles
pacinian corpuscles
tactile sensation
superficial layer
deep layer
fine downy hair-fetus hair
short fine pale hair- barley visible
long course heavily growing hair
color is dermined by?
lanugo
vellus
terminal
melanin
produce keratin- tough fibrous protein providing protection
produces melanin-protects against uv ray
macrophages- from red bone marrow
touch receptors
keratinocytes
melanocytes
langerhans
merkel
lesions of the skin-benign
cancer of the melanocytes
nevi
malignant melanoma
superficial-dermal papillae, corpuscles of touch and free nerve endings
deep- adipose cells, hair bulb, nerves, oil glands
tears or excessive
stretching leaves marks
striae
superficial- papillary region
deep- reticular region
above the skin surface
penetrates the dermis
surrounds the root-external and internal
epithelial rooth sheath(inner)
dermal root sheath(outer)
shaft
root
follicle
hair follciles- secrete sebum
prevents dehydration of haur abd skin
inhibits growth
sebaceous oil gland