epidermal layers

Stratum corneum (cornified/keratinized cells)

stratum lucidem (mostly in foot pads)

stratum granulosum (purple granular cells)

stratum spinosum (desmosome prickle cells)

stratum basale (always dividing, attach to basement membrane)

in the stratum basale

make melanin and can pass it to keratinocytes

(not all pigmented cells are melanocytes)

stratum spinosum and stratum basale

can't be seen w light microscope

similar to macrophage

stratum basale

clear cells, hard to see

neuroendocrine - regulate hair cycles

mechanoreceptors and nerves associated

present in high friction areas

interdigitate with dermal papilla

collagen, reticular, elastic fibers

ground or interstitial substance

blood and lymph vessels

nerves

melanocytes, lymphocytes, mast cells

epidermal: reptiles and non feathered parts of birds, projections of stratum corneum

dermal scales: fish and sharks, bony scales arising from the dermis (painful to remove!)

cuticle

cortex

medulla

outer root sheath

inner root sheath

matrix

 dermal papilla

granular cell layer

makes flaky keratin

lacks granular cell layer

makes homogenous keratin

glassy cells

large diameter

deeply rooted in dermis

sebaceous glands, apocrine glands, arrector pili

smaller diameter

rooted more superficially

may have sebaceous glands

no aporine or arrector pili

anagen phase

catagen phase

telogen phase

growth phase

extends deeper into the dermis with suprabulbar/bulbar portion

transitional or involuting phase

suprabulbar/bulbar portion regresses

resting phase

suprabulbar/bulbar portion lost

hair is eventually shed