1. Section 36-3: Integumentary System (Skin)
* Includes skin, hair & nails
* Skin = largest organ of human body

2. Functions of the Skin:
1. Regulate body temp.
a. Blood vessels
When hot, vessels dilate & release heat as blood flow increases

3. When cold, vessels constrict & heat is conserved
b. Sweat – released by glands to cool body

4. 2. Senses – sensory neurons
detects hot/cold, pressure & environ. conditions
3. Vitamins – when exposed to UV light, makes vitamin D
helps absorb calcium

5. 4. Remove Wastes
Sweat – releases excess water, salts & urea
5. Protection from…
Physical & chemical damage
Disease (1st line of defense)

6. 3 Layers of Skin:
Epidermis – outermost layer made of dead cells & constantly replaced
a. Keratin – protein that…
makes nails
gives tough texture
“waterproof” quality

7. b. Melanin – pigment that…
colors the skin
protects cells from sun damage
more sun exposure makes more melanin

8. 2. Dermis – inner, thicker portion of skin
Contains:
Nerves
Blood vessels
Hair follicles (warmth & protects)
Sweat glands
Oil glands – soften skin

9. 3. Subcutaneous Layer (Hypodermis)
Mostly fat deposits
Absorb impact
Retain heat
Store food

10. How Cuts Heal
1) Blood clots & cut closes
2) New cells push damaged cells to surface
3) Scab forms & WBC fight wound infection
4) New cells fill in gap of scab