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Integumentary system | "covering" 2 regions |
2 regions of integumentary system | 1. epidermis
2. dermis |
epidermis | epithelial cells
outer most shield
avascular+ innervated
gets nutrients from dermis by diffusion |
Dermis | much thicker and tougher.
made of fibrous conn. tissue
vascularized |
Hypodermis( Superficial Facia) | deep to the skin.
contains fat/adipose tissue and some areolar
stores fat and anchors to muscle and allows skin to slide
shock absorber, contains unwanted fat. |
epidermis | keratinized strat. squamos
-4 cell types
-4~5 layers |
4 cells of epidermis | 1.keratinocytes
2.melanocytes
3.langerhan
4.merkel |
Keratinocytes | -most numerous. makes keratin
-increased in areas with more friction(hands/feet)
-tightly bound by desmosomes
-highly mitotic(dividing)
-cells dead at surface
-24-45 day life span |
melanocytes | -makes melanin
-make colored pigment in deepest epidermis
-spidershaped. arims that touch every keratinocyte in basal layer
-melanin travels to top layer..protects from uv rays |
langerhan's cells | -rise from bone marrow. move to epidermis
-asters go around keratinocytes
-phagocytes that take in foreign substances& help activate immune system |
Merkel Cell | -spiky hemisphere shape
-in epidermal with dermal junction
each is connected to a sensory disclike nerve called merkel disc. |
Merkel disc | senses touch |
Layers of Epidermis | 4-5 layers
-5 in thicker skin areas
s=stratum
s. Basale
s. Cornuem
s. lucidem
s. spinosum
s. granulosum |
s. basale
(bottom layer) | deepest, attached to the dermis
-single layer of cells. has youngest keratinocytes
-germinating layer(growing)
-highly mitotic
-aka. Stratum germinativum
-high # of melanocytes(10-25% of layer) |
Stratum Germinativum | s. basale |
s. Spinosum | -7 cell layers thick
-contain weblike system~ Intermediate filaments
-prickly name from shrinking due to diminishing nutrients yet maintains desmosomes
-langerhan's cells most abundent |
Intermediate Filaments | tension resisting bundle of keratin.
- in stratum spinosum |
s. Granulosum (granular layer) | -cells flattened, nuclie disappear& accumulate
- has 2 granules
-cells die above this layer |
Granules in s. Granulosum | !. keratohyaline- keratin aggregation
2. lamellated granules- water proof glycolipids. "plated" |
S. lucidem | -"clear layer"
-only present in thick skin
-thin translucent layer
-flattened keratinocytes
-keratohyaline attaching to keratin |
s. coreum | -horny layer
-75% of epidermis
-20-30 cell layers thick
mostly dead calls
-aids in avoiding abrasions
-dandruff comes from this
-average person will shed 40 lbs/lifetime |