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

Skin Single largest organ of the body

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

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.

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”

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. http://cnx.org/content/m19916/latest/

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.

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

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

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”

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?

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)

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.