T/F skin is the largest organ
T/F hypodermis is not actually part of the "skin"
T (just fat underneath)
Embryology of 3 layers
epidermis: from ectoderm
hypodermis and dermis: from mesoderm
melanocytes develop from which embryonic layer
ectoderm (like epidermis)
4 major cells in the skin
tactile epithelial (Merkel discs)
most common cell type in skin
keratinocytes (keratin=protection, in all epidermis layers)
what are dendritic cells?
macrophage-like (in stratum spinosum)
merkel discs are in which layer
melanocytes: fxn and layer
stratum basale (w/ merkel discs)
T/F stratum basale has cells that continuously undergo mitosis
what happens to keratinocytes as they move "up" the epidermis
cytoplasms fill with keratin (that they make!)
describe a keratinocyte at the end of it's life
dead, flat sac of keratin in the stratum corneum
how long does it take Henna to shed?
get entirely new skin about every month (a liittle longer)
what's a callus
thickening of epidermis due to ^ friction
T/F keratin is an extracellular protein for skin protection
F (fills cytoplasm)
which layer is only in thick skin?
why dermal papillae?
b/c epidermis nonvascular, but needs nutrients to keep basale alive and dividing
T/F stratum basale is the thinnest layer in the epidermis
T (nearly single row of cells)
what are the "spider shaped" cells of the epidermis
melanocytes; lanky processes give melanin to keratinocytes
why does light complexion=freckles?
light complexing=low melanin (blocks UV), so UV penetrates better to basale, where freckles are made
problem with suntans?
^sunlight=^melanin=blocks UV=no more vit D!
what's Vit D do?
takes Ca from food = strong bones
lack enzyme to make melanin
2 other skin pigments?
carotene (from carrots, can accumulate in corneum)
hemoglobin (if too low melanin, you can see blood)
what IS a freckle? mole?
clumps of melanin
why does a mole form?
clusters of melanocytes fail
cancerous mole types? (from least to most serious)
(least) basal cell carcinoma
squamous cell carcinoma
where are dendritic cells found?
what's the "clear layer" in the skin
lucidum (thick only)
"leather" of the skin?
what/where are the 2 nerve plexes of the dermis?
pacinian (deep=reticular layer)
fiber type of the dermal layers?
papillary = areolar CT (loose CT)
reticular = dense irregular CT
T/F fingerprints and flexure lines are a result of stuff in the dermis, rather than the epidermis
varying density of collagen causes...
cleavage/tension lines, in reticular dermis
where does it go where you eat hella Chipotle
rule of 9s?
glands next to hair?
what secrete true sweat?
what determines hair type
shape of C.S