1. Dermal Layers Chapter 4

2. Dermal Layers Skin is a m________ and is made of e__________ tissue and c_________ tissue. The e______ layer is called the e__________. The c_________ tissue layer is called the d________. Below these two layers is another layer which is not part of the skin, but is still vital to the skin’s function. This layer is called the s_______ ____ layer, or the h___________. This layer consists of adipose tissue. membrane epithelial connective epithelial epidermis connective dermis subcutaneous hypodermis

3. Epidermis Outermost layer of the skin 4 or 5 layers – Stratum corneum – (Stratum lucidum) – Stratum granulosum – Stratum spinosum – Stratum basale Stratified squamous epithelial tissue – Avascular

4. Epidermis

5. Functions – Prevents water loss (keratinized cells of stratum corneum) – Keeps out disease-causing microorganisms

6. Stratum Basale Deepest epidermal layer Closest to dermis 1-cell thick Cell division – Pushes older cells toward surface of the skin Basement membrane is deep to stratum basale

7. Stratum Spinosum Superficial to stratum basale Several cells thick Less cell divison Flattened/irregular cells Spinelike projections from cells

8. Stratum Germinativum Stratum basale + Stratum spinosum = Stratum germinativum Growing layers – Where cell division occurs

9. Stratum Granulosum Superficial to stratum spinosum Very thin, 2-3 cells thick As cells move up from the stratum basale, they die and become flatter Keratinization – Older cells harden – Keratin protein

10. Stratum Lucidum Bonus layer Thickened skin of palms and soles

11. Stratum Corneum Most superficial layer of epidermis Many layers of tough, tightly packed dead epidermal cells – Thickest layer of the epidermis (20-30 cells thick) Dead cells completely filled with keratin – Water resistant 30-40 days from creation in stratum basale until flake off at stratum corneum

12. Epidermis

13. Cells of the Epidermis Stem cells – undifferentiated cells found only in stratum basale Keratinocytes – cells that make keratin (most cells in epidermis) Melanocytes – make melanin, found only in stratum basale Merkel cells – touch receptors, attached to nerve cells Dentritic cells (Langerhans cells) – macrophages that guard against foreign microbes/pathogens, alert immune system

14. Dermis Deep to epidermis Binds epidermis to underlying tissues Blood vessels in the dermis supply nutrients to all layers of the skin Dense connective tissue 2 layers – Papillary layer – Reticular layer

15. Papillary Layer Areolar connective tissue Lots of blood vessels Dermal papillae – Capillary loops – Sensory cells – Fingerprints

16. Reticular Layer Dense connective tissue Stretch marks – Dermal tearing

17. Hypodermis Subcutaneous layer – Sub- = – Cut- = Deep to the dermis Adipose, loose connective tissues – Insulation – Major blood vessels Infants/elderly have less, more sensitive to cold below skin

18. HOMEWORK Epidermis worksheet Period 6 membrane worksheet too.