1. Body Systems
Integumentary

2. SKIN Major organ- largest
Barrier against pathogens,regulates body temperature, removes waste,protects from UV rays
2 layers- epidermis and dermis

3. Epidermis Outermost layer 2 layers- exterior and interior
Exterior layers of DEAD cells- these flake off as living interior layer grows and pushed off dead cells.
Exterior layer has Keratin that helps protect lower layers from sun, chemicals, bacteria

4. Interior layer- cells contain melanin-pigment that changes color due to sun exposure.
As you tan( meaning the interior layers change color) the interior cells will continue to move upward to become part of the exterior layer and be shed off. Every 28 days your cells shed off- so this helps explain why your tan fades.

5. DERMIS Thick part of skin
Contains blood vessels, nerves, hair follicles and sweat glands.

6. Function of skin
Maintain homeostasis by regulating temperature- when you are hot, the vessels in the dermis dilate and move closer to the surface to release heat. When you are cold- vessels constrict and move deeper into the dermis to conserve heat

7. Sweat glands produce sweat to also help control body temperature
Sweat glands produce sweat to also help control body temperature. When sweat evaporates this cools the skin and heat is lost.
Sebaceous glands(oil glands) produce oil to help keep epidermis flexible and waterproof
Nerve cells in dermis receive stimulus from outside.
Produces vitamin D that helps your body absorb calcium.
1st line of defense against pathogens-skin pH about 3-5.It’s also slick due to chemicals and secretions. Pathogens have a hard time sticking.

8. Injury to Skin
Cuts and scrapes repaired by cells of the dermis filling in the gap.
Scab may form if cut is deep- clot forms from red blood cells in blood vessel. Scab will fall off and replaced by new skin.

9. Skin Cancer
Prolonged exposure to sun can cause abnormal growth of cells.
How can you prevent over exposure to UV ray?
Hat
Clothing
sunglasses
Sunscreen
Limit time in sun

10. Hair and Nails
Made of Keratin(keratin also makes up horns, scales, feathers, quills, hoofs)
Hair provides UV ray protection and insulation
Hair in ears and nose and eyelashes provide protection against particles from entering body
Hair grows from hair follicles found in the skin
Nails grow from the nail root