Epidermis Made of stratified epithelium Provides mechanical support/keeps

microorganisms out 2 kinds

– Thick- 5 layers up to .5mm thick (palms/feet)

– Thin- 4 layers up to .08mm thick

Stratum germinativum

Structure

–Attached to the basement membrane created by the joining of the epidermis and dermis

–Forms dermal ridge, which creates fingerprints

Stratum germinativum Cells

–Basal (germinative cells)- divide to replace old skin

–Merkel cells- sensitive to touch, found on skin that lacks hair

–Melanocytes- contain pigment melanin that gives skin the brown color

Stratum Spinosum Structure

– 8-10 layers of keratinocyte cells. Basal cells divide becoming keratinocytes and are pushed up into this layer

Cells

– Langerhans Cells- recognize foreign microorganisms

Stratum Granulosum Structure- 3-5 layers of keratinocyte cells Cells no longer divide, and begin to

produce keratin (protein in hair & nails) Production of keratin causes the cells to

flatten and dehydrate, eventually they die

Stratum lucidum

The extra 5th layer found in thick skin

Clear layer of very densely packed keratin

Stratum Corneum Outer 15-30 layers of keratinized cells Cells are dead, thin, filled w/ keratin fibers Keratin fibers interlock with one another

creating thick protective layer Outer most layer will shed in sheets Takes cells 15-30 days to reach this layer

and they stay there up to 2 weeks

Skin Color/Vitamin D

Determined by pigments, carotene and melanin

•Vitamin D is made when skin is exposed to sunlight, this vitamin helps make the hormone calcitriol, which helps w/ absorption of calcium