1. Structure of the Skin Notes EQ: Describe the three layers of the skin. EQ: Identify and locate accessory structures of the skin.

2. Skin Facts Largest organ in the body. Most of the dust in your home is really dead skin. Skin accounts for about 15% of your body weight. You grow a completely new layer of skin every 28 days. Over 1000 species of bacteria are naturally found on human skin.

3. Layers of the Skin Cutaneous membrane Epidermis + dermis

4. Layers of the Skin Epidermis mostly dead cells Thick skin – 5 layers; hands and feet Thin skin – 4 layers; everywhere else Melanocyte – produce skin pigment (melanin)

5. Squamous epithelium

6. Layers of the Skin Dermis Living cells Nerves, blood vessels, glands, collagen and elastin

7. Dermal Tissue

8. Layers of the Skin Hypodermis (subcutaneous layer) Mostly adipose (fat) tissue Hair follicles

9. Hypodermal Cells

10. Accessory Structures of the Skin A – hair shaft B – sebaceous gland –Produce sebum –Lubricate hairs –Antibacterial C – hair follicle

11. Acne Formation

12. Accessory Structures of the Skin D – arrector pili muscle –Make hair stand up E – sweat gland –Homeostasis - as sweat evaporates, it cools the body –Body odor

13. Accessory Structures of the Skin F – blood vessel –Bring nutrients to skin cells –Homeostasis – warms the skin G – nerve receptor –Touch –Pain –pressure

14. Functions of the Skin Notes EQ: What are the functions of the skin in the human body?

15. Recurring Theme Homeostasis –Means “steady state” –The body has mechanisms to keep its internal conditions the same when the environment changes

16. Function of Epidermis Protection –Bacteria –Dirt –Minor wounds Melanocytes –Protection from UV

17. Function of Dermis Makes skin elastic and tough –Collagen –Elastin –Fibrillin Homeostasis – “goose bumps” caused by arrector pili muscles create insulation

18. Function of Hypodermis Insulation Padding Energy storage

19. Functions of Accessory Structures Hair –Homeostasis - warmth –Touch sensitivity –Protection from injury Melanocyte –Produces melanin –Protects from UV rays