1. Integumentary System Skin Epidermis

2. Skin Layers Stratified Squamous Epithelium Epidermis (upper) Dermis (lower)

3. Stratum Corneum Uppermost layer Thin, flat cells

4. Stratum Corneum

6. Dead and NO nuclei Continually shed

7. Stratum Corneum  Thick Cell membranes  Desmosomes present - strong

8. Stratum Corneum Keratinocytes – cells full of Keratin

9. Stratum Corneum Dry cells – Can act like a sponge – Prune look on soaking Latin for “horny layer”

10. Stratum Corneum

11. Provides barrier to – Water – Chemicals – Bacteria

12. Stratum Corneum Hyperkeratosis  Abnormal thickening of this layer  Dry and scaly skin

13. Stratum Corneum Hyperkeratosis

14. Epidermis Stratum Lucidum 2 nd Layer (3-4 layers) Prevents water loss

15. Stratum Lucidum Present in “Thick” skin – Hand Palms – Soles of feet

16. Stratum Lucidum Clear layer – Contains eleiden Protein becomes keratin Dead with NO nuclei

17. Stratum Lucidum

18. Stratum Granulosum 3 rd Layer (3-4 layers) Cells starting to die – Lysosomes – Degeneration of nuclei

19. Stratum Granulosum Granules present – Produce keratin – Keratinization begins here

20. Stratum Granulosum

22. Stratum Spinosum 4 th Layer (8-10 layers) Irregular-shaped cells

23. Stratum Spinosum Desmosomes – Connections between cells – “cell-to-cell adhesion”

24. Stratum Spinosum  If desmosomes are weakened, cells pull apart  As a result of exposure to chemicals, heat, or friction

25. Stratum Spinosum  Result: Blister  3. cross out

26. Stratum Spinosum Gives a “spiny” appearance

27. Stratum Spinosum

30. Heavy keratin production – Lots of RNA – Protein synthesis

31. Stratum Basale Lowest layer of epidermis

32. Stratum Basale Single layer – Simple Columnar looking cells – Looks like a line of fence posts

33. Stratum Basale

35. Mitosis occurs here Cells migrate to surface (35 days)

36. Stratum Basale Pressure over time – Increases mitosis – Results in callus

37. Epidermis – Layers Stratum Basale Stratum Spinosum Stratum Granulosum Stratum Lucidum Stratum Corneum