1. The Skin

2. Your Largest Organ The skin is your body’s LARGEST organ! Fun Facts:
The average person's skin covers an area of 2 square meters. 
Skin accounts for about 15% of your body weight.
The average adult has approximately 21 square feet of skin, which weighs 9 lbs and contains more than 11 miles of blood vessels.

3. Skin Structures Made up of 3 layers of tissue Epidermis Dermis
Fatty Layer

4. Epidermis Outer, thinnest layer of your skin
Outermost cells are dead and water repellent
1,000s of epidermal cells rub off every time you take a shower, shake hands, blow your nose, etc.
New cells are produced constantly at the base of the epidermis

5. Epidermis Continued…
Cells in the epidermis produce the chemical melanin.
Melanin is a pigment that protects your skin and gives it color (your eyes, too).
Different amounts of melanin results in different skin colors
When skin is exposed to UV rays, melanin production increases and skin becomes darker
Lighter skin tones = less protection = burns more easily

6. Dermis The layer of cells directly below the epidermis
Thicker than the epidermis
Contains blood vessels, nerves, muscles, oil and sweat glands
Below dermis is the fatty region that insulates the body
This is where much of the fat is stored when a person gains weight

7. Dermis Continued…
Blood vessels: a tubular structure carrying blood through the tissues and organs
Nerves: special cells that carry messages from one part of the body to another
Oil glands: a small gland that secretes an oily or waxy matter to lubricate and waterproof the skin and hair of mammals.
Sweat glands: a small gland that secretes sweat and excretes waste

8. Skin Functions Protection = Most important function Sensory response
Special nerve cells detect and relay information to the brain, which makes your skin a sensory organ
This is why you can sense the softness of a blanket, sharpness of a needle, heat of a frying pan, etc.
Formation of vitamin D
Small amounts of vitamin D are produced when your skin is exposed to UV light (sunlight)
Essential for good health
Helps body absorb calcium into blood from food in digestive tract
Skin forms a protective covering over the body that prevents physical and chemical injury. Some bacteria and other disease-causing organisms cannot pass through the skin as long as it is unbroken. Glands in the skin secrete fluids that can damage or destroy some bacteria. The skin also slows down water loss from body tissues.

9. Skin Functions Continued…
Regulation of body temperature
Blood vessels help release or hold heat
Blood vessels expand blood flow increases heat is released
Blood vessels contract blood flow decreases less heat is released
Adult human dermis has about 3,000,000 sweat glands
These help regulate body temperature and excrete wastes
Blood vessels dilate - pores open in the skin that lead to the sweat glands - sweat then moves out onto the skin – heat transfers from body to sweat on the skin – sweat evaporates – removes the heat and cools the skin.
Eliminates excess heat produced by muscle contractions

10. Skin Functions Continued…
Ridding the body of wastes
As your cells use nutrients for energy, they produce wastes
If not removed from your body, these wastes can act as poisons
Sweat glands also release water, salt and other waste products
If too much water and salt are released by sweating, you might feel light-headed or may faint

11. Skin Injuries and Repair
A bruise is the bursting of the tiny blood vessels beneath the skin
Red blood cells leak into surrounding tissue
These blood cells break down and release hemoglobin
Hemoglobin breaks down into pigments
The color of these pigments causes bruised area to turn shades of blue, red and purple
After all pigment is absorbed into the bloodstream, the bruise disappears and skin looks normal

12. Cuts A cut is any tear in the skin
Blood flows out, then a clot forms over it
Scab forms to prevent bacteria from entering the body
Scab falls off, leaving new skin behind
Cells in surrounding blood vessels fight infection while the skin cells beneath the scab grow to fill the gap in the skin
Scars form when a cut is big enough and it’s the large amounts of thick tissue fibers that form