• Your skin, hair, and nails make up your Your skin, hair, and nails make up your integumentary systemintegumentary system

• Integument means “covering”Integument means “covering”

• Like all organ systems, the Like all organ systems, the integumentary system helps your body integumentary system helps your body maintain a healthy internal environment.maintain a healthy internal environment.

• Skin protects you by keeping moisture in your body and Skin protects you by keeping moisture in your body and foreign particles out of your bodyforeign particles out of your body

• Skin keeps you “in touch” with the outside world. The Skin keeps you “in touch” with the outside world. The nerve endings in your skin allow you to feel what’s around nerve endings in your skin allow you to feel what’s around youyou

• Skin helps regulate your body’s temperature. For Skin helps regulate your body’s temperature. For example, small organs in the skin called example, small organs in the skin called sweat sweat glandsglands produce sweat, a salty liquid that flows to the produce sweat, a salty liquid that flows to the surface of the skin. As sweat evaporates, the skin cools.surface of the skin. As sweat evaporates, the skin cools.

• Skin helps get rid of wastes. Several types of waste Skin helps get rid of wastes. Several types of waste chemicals can leave the bloodstream and be removed in chemicals can leave the bloodstream and be removed in sweat.sweat.

• A darkening chemical in skin called A darkening chemical in skin called melaninmelanin determines skin color determines skin color

• If a lot of melanin is present, the skin iv If a lot of melanin is present, the skin iv very darkvery dark

• If only a little melanin is produced, the If only a little melanin is produced, the skin is very light.skin is very light.

• Melanin in the upper layer of the skin Melanin in the upper layer of the skin absorbs much of the harmful radiation absorbs much of the harmful radiation from the sun, reduction DNA damage that from the sun, reduction DNA damage that can lead to cancercan lead to cancer

•The The epidermisepidermis is the thinner is the thinner layer of the two. It is what layer of the two. It is what you see when you look at you see when you look at your skinyour skin

•The deeper, thicker layer is The deeper, thicker layer is known as the known as the dermisdermis

EpidermisEpidermis• The epidermis is composed of a type of The epidermis is composed of a type of

epithelial tissue.epithelial tissue.• The epidermis is only as thick as two sheets of The epidermis is only as thick as two sheets of

notebook paper over most of the bodynotebook paper over most of the body• It is thicker in the palms of your hands and the It is thicker in the palms of your hands and the

soles of your feet.soles of your feet.• Most epidermal cells are dead and are filled Most epidermal cells are dead and are filled

with a protein called keratin, which helps with a protein called keratin, which helps make the skin tough.make the skin tough.

DermisDermis• The dermis lies underneath the The dermis lies underneath the

epidermisepidermis• It is mostly connective tissue, and It is mostly connective tissue, and

it contains many fibers made of a it contains many fibers made of a protein called collagenprotein called collagen

• The fibers provide strength and The fibers provide strength and allow skin to bend without tearingallow skin to bend without tearing

• A hair is formed at the bottom of A hair is formed at the bottom of a tiny sac called a hair folliclea tiny sac called a hair follicle

• The hair grows as new cells are The hair grows as new cells are added at the hair follicle and added at the hair follicle and older cells get pushed upwardolder cells get pushed upward

• The only living cells in a hair are The only living cells in a hair are in the hair folliclein the hair follicle

• Hair protects skin from ultraviolet Hair protects skin from ultraviolet light and keeps dust and insects out light and keeps dust and insects out of your eyes and nose.of your eyes and nose.

• Hair gets its color from the Hair gets its color from the pigment melaninpigment melanin

• Dark hair contains more melanin Dark hair contains more melanin than blond hairthan blond hair

• Hair helps regulate body Hair helps regulate body temperaturetemperature

• A contraction of a tiny muscle attached to A contraction of a tiny muscle attached to the hair follicle causes the follicle to bendthe hair follicle causes the follicle to bend

• The bending follicle pushes up the The bending follicle pushes up the epidermis to make a goose bumpepidermis to make a goose bump

• If the follicle contains a hair, the hair If the follicle contains a hair, the hair “stands up”“stands up”

• The lifted hairs function like a sweater to The lifted hairs function like a sweater to trap warm air around the bodytrap warm air around the body..

• Nails protect the tips of your fingers Nails protect the tips of your fingers and toes so that they can remain soft and toes so that they can remain soft and sensitiveand sensitive

• Nails form from nail roots under the Nails form from nail roots under the skin at the base and sides of nailsskin at the base and sides of nails

• As new cells form, the nail grows As new cells form, the nail grows longerlonger