1. Integumentary System The Skin You’re In 20 square feet 40 lbs shed in your lifetime

2. The Skin It is the largest organ in the body, although it is easily infected because of its location.

3. Functions 1.Protection- Outer most wall of defense a. Physical barrier: abrasions, dehydration, UV radiation (aids in production of vitamin D) b. Biological barrier: microbes (bacterial, fungal, etc.) 2. Sensation- a. Skin acts as a big sensory organ (temp, pain, pressure) b. Keeps body informed of changes in environment

4. 3. Temperature Regulation- a. Regulates sweat secretions b. Regulates blood flow c. Goose Bumps PST…

5. cutaneous membrane Remember: Membranes must have 2 tissue layers What are the two layers found in epithelial membranes? Epithelium and connective What are the two layers found in skin? Epidermis and Dermis

6. The Structure of Skin Epidermis – superficial, thin in some areas of the body and thicker in others Dermis – intermediate, thicker, connective tissue layer. Subcutaneous layer (hypodermis) – deep tissue layer that attaches skin to underlying structures. What type of tissue must that be?

7. Epidermis Its avascular Types of cells – Keratinocyte – cells that produce keratin (protein) Keratinization – process of filling skin cells with keratin as they migrate to the surface, which helps the skin as these cells reach the surface. The process takes about 2-4 weeks. – Melanocyte (also found in dermis) – cells that produce melanin – pigment used to color skin, eyes and hair.

8. Epidermis Continued – Langerhans cells- part of the immune response; easily damaged by UV rays – Merkel cell (found in the deepest layer of hairless skin) – thought to function in sensation of touch.

9. Epidermis is Composed of Five Sublayers Superficial (outer) » Stratum cornea » Stratum lucidium » Stratum granulosum » Stratum spinosum » Startum basale Deep (inner) Bob’s Sister Grace Loves Corn

10. Epidermis Layers Stratum corneum – 30 layers of dead cells – Cells are completely full of keratin – As new cells ascend old cells slough off

11. Layers of the Epidermis Stratum lucidum – Formed from dead cells of the deeper strata – Occurs only in thick, hairless skin of the palms of hands and soles of feet

12. Epidermis Layers Stratum granulosum – 2 to 5 layers thick – Cells are becoming flattened Stratum spinosum – 8 to 10 layers – Production of Keratin begins

13. Layers of the Epidermis Stratum basale – Superficial to the dermis – Cells undergoing mitosis – New cells become the more superficial layers – Dermis and Stratum Basale form wavy border Thin layer

14. In Epidermis Layer Melanin Pigment (melanin) produced by melanocytes Melanocytes are mostly in the stratum basale Amount of melanin produced depends upon genetics and exposure to sunlight