1. The Integumentary System (in-teg-yoo-MEN-tuh-ree)
Skin, Hair and Nails
The functions of this system:
provide a barrier against infection and injury
helps to regulate body temperature
removes wastes from the body
provides the sense of touch

2. Skin Single largest organ of the body

3. Epidermis – outer layer of skin
Protects against infection
Contains no blood vessels
The outermost part of the epidermis is made up of dead skin cells.
You are likely to shed some 40 pounds of skin in a lifetime
~80% of household dust is dead skin cells

4. Epidermis – outer layer of skin - continued
The epidermis contains melanin - a dark brown pigment that protects the skin from sun damage.
Most people have about the same number of melanocytes (cells that produce melanin).
The amount of melanin they produce is what makes the difference in skin color.

5. Dermis – inner layer of skin
The dermis contains blood vessels. On cold days these blood vessels narrow to limit heat loss. On hot days the blood vessels widen allowing the body to cool off.
Sweat Glands – another way to cool the body. When sweat evaporates it cools the body. Sweat also gets rid of wastes.
Oil Glands – secrete sebum, an oily substance that waterproofs our skin and keeps our skin and hair flexible.
Homeostasis – “keeping things in balance”

6. Dermis – continued
Nerve Endings - The dermis is filled with many tiny nerve endings which give you the sense of touch. These nerve endings send messages to the brain letting you know if something is hot or cold or if something is hurting. Some parts of your body have more nerve endings than others.

7. Subcutaneous Layer (Hypodermis)
Beneath the dermis is a subcutaneous layer of fat. This fat aids in the process of homeostasis, by forming a layer of insulation to slow heat loss.

8. Hair Hair covers almost every exposed surface of the body.
Hair on your head keeps you warm and protects from UV rays of the sun.
Hairs in your nostrils, external ear canals and eyelashes keep dirt from entering the body.
Hair grows approx. 1 cm a month
Average head has around 120,000 hairs

9. Nails
Nails – protect finger tips and toes. Made from keratin, a tough protein.
Finger nails grow four times as fast as toe nails.
Nails grow approx. .5 mm per week
Ripley’s Believe it or Not

10. Maintaining Homeostasis
The following are examples of how the integumentary system helps to maintain homeostasis:
Sweating helps our bodies cool down
Sweating gets rid of wastes
Skin protects us from UV rays
Hair prevents heat loss
Layer of fat prevents heat loss
Skin works with platelets to clot blood and form scabs. This prevents too much blood loss and protects against infection.
Homeostasis – “keeping things in balance”

11. Why???
Why does it hurt less to step on something sharp with the heel of your foot than to touch something with the tip of your toe?
Why don’t you bleed with a slight scratch?

12. Integumentary System Hair, skin and nails Functions of this system:
provide a barrier against infection and injury
helps to regulate body temperature
removes wastes from the body
provides the sense of touch
Epidermis – outermost layer of skin
Dermis – inner layer of skin. Contains blood vessels, oil glands, sweat glands, nerve endings, hair follicles
Hypodermis – subcutaneous layer (layer of fat)

13. Do not write on this page. Leave it blank.
Homeostasis
Keeping our bodies in balance
Examples of how the integumentary system helps to maintain homeostasis:
Sweating helps our bodies cool down
Sweating gets rid of wastes
Skin protects us from UV rays
Hair prevents heat loss
Layer of fat prevents heat loss
Skin works with platelets to clot blood and form scabs. This prevents too much blood loss and protects against infection.
Do not write on this page. Leave it blank.