2. Epidermis 4 Made of stratified epithelium 4 Provides mechanical support/keeps microorganisms out 4 2 kinds –Thick- 5 layers up to.5mm thick (palms/feet) –Thin- 4 layers up to.08mm thick

4. Stratum germinativum 4 Structure –Attached to the basement membrane created by the joining of the epidermis and dermis –Forms dermal ridge, which creates fingerprints

6. Stratum germinativum 4 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

7. Stratum Spinosum 4 Structure –8-10 layers of keratinocyte cells. Basal cells divide becoming keratinocytes and are pushed up into this layer 4 Cells –Langerhans Cells- recognize foreign microorganisms

8. Stratum Granulosum 4 Structure- 3-5 layers of keratinocyte cells 4 Cells no longer divide, and begin to produce keratin (protein in hair & nails) 4 Production of keratin causes the cells to flatten and dehydrate, eventually they die

9. Stratum lucidum 4 The extra 5th layer found in thick skin 4 Clear layer of very densely packed keratin

10. Stratum Corneum 4 Outer 15-30 layers of keratinized cells 4 Cells are dead, thin, filled w/ keratin fibers 4 Keratin fibers interlock with one another creating thick protective layer 4 Outer most layer will shed in sheets 4 Takes cells 15-30 days to reach this layer and they stay there up to 2 weeks

12. 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