the skin

The Skin

• Skin is the largest organ of the body.• It is part of the integumentary system. • The integumentary system is made up of all of

the external coverings of the body, including the skin, nails, and hair.

• Like your bones and muscles, skin has many different functions in your body.

the skin

Protection• Skin covers your bones and muscles, protecting

them from the outside environment. • Skin keeps your body from drying out in sunlight

and wind. • Skin also protects the cells and tissues under the

skin from damage. • Skin keeps dirt, bacteria, viruses, and other

substances from entering your body.

functions of the skin

Sensory Response• Your skin has sensory receptors

that detect texture. • Sensory receptors in the skin

also detect temperature and sense pain. • The more sensory receptors there are in an area

of skin, the more sensitive the skin is.

functions of the skin

Temperature Regulation• Skin helps control body temperature. • Skin has tiny holes, or pores, on

its outer surface. • When you exercise, sweat comes

from these pores. Sweating is one way that skin maintains normal body temperature.

• As sweat evaporates, excess thermal energy leaves the body and the skin cools.

functions of the skin

Temperature Regulation• Another way the skin maintains body

temperature is by releasing thermal energy from blood vessels.

• When your body temperature begins to increase, such as when you are exercising, blood vessels near the skin’s surface dilate, or enlarge.

• This increases the surface area of the blood vessels and releases more thermal energy.

functions of the skin

Temperature Regulationfunctions of the skin

blood vessels dilate to release heat

Production of Vitamin D• If your skin is exposed to sunlight, it can make

vitamin D.• Your body needs vitamin D to help it absorb

calcium and phosphorus. • Vitamin D also helps bones grow.

functions of the skin

Elimination• Normal cellular processes produce waste

products. • The skin helps eliminate, or get rid of,

some of these wastes.• Water, salts, and other waste products are

removed through the pores of the skin. • Elimination occurs all the time, but you probably

only notice it when you sweat.

functions of the skin

• The skin that you see and feel on your body is the outermost layer of your skin. Below it are two other layers of skin.

• Each layer has a different structure and function.

structure of the skin

structure of the skin

Epidermisstructure of the skin

• The epidermis is the outermost layer of skin and the only layer in direct contact with the outside environment.

Epidermisstructure of the skin

• The epidermis is thin but tough. The epidermis on your eyelids is thinner than a sheet of paper.

Epidermisstructure of the skin

• Cells of the epidermis are constantly shed, or gotten rid of, and replaced by new cells

Epidermisstructure of the skin

• One important function of the epidermis is the production of melanin.

• Melanin is a pigment that protects the body by absorbing some of the Sun’s damaging ultraviolet rays.

Dermisstructure of the skin

• Below the epidermis is the dermis.• The dermis is a thick layer of tissue that gives

skin strength, nourishment, and flexibility.

Dermisstructure of the skin

• The dermis contains sweat glands, blood vessels, nerves, hair follicles, and muscles.

• When the muscles in the dermis contract, you get goose bumps.

Fatty Layerstructure of the skin

• The innermost layer of skin is sometimes called the fatty layer.

• It insulates the body, keeping it warm.

skin injuries and repair

• Skin is often injured because it is exposed to the outside environment. You might have injured your skin by falling down or bruising it.

• Your body has different ways to repair skin. The type of repair depends on the type of injury and how serious it is.

skin injuries and repair

• A bruise is an injury where blood vessels in the skin are broken, but the skin is not cut or opened.

• The broken blood vessels release blood into the surrounding tissue, forming the bruise.

• Bruises usually change color as they heal. This change in color is due to chemical changes in the blood under the skin’s surface.

Bruises

skin injuries and repair

skin injuries and repair

• When you break one or more layers of skin, a cut results.

• Cuts often cut blood vessels, too. • Blood that flows from a cut usually thickens and

forms a scab over the cut. • The scab helps keep dirt and other substances

from entering the body.

Cuts

skin injuries and repair

• Skin heals by making new skin cells that repair the cut.

• Some cuts are too large to heal naturally. • If that happens, stitches might be needed to

close the cut while it heals.

Cuts

skin injuries and repair

• A burn is an injury to your skin or tissues that can be caused by touching hot objects.

• Touching extremely cold objects, chemicals, electricity, radiation (such as sunlight), or friction (rubbing) can also cause burns.

• There are three degrees, or levels, of burns.

Burns

skin injuries and repair

skin injuries and repair

skin injuries and repair

healthy skin

• Another way to keep your skin healthy is to eat a balanced diet.

• You can also use gentle soaps to clean your skin and lotion to keep your skin moist.

the skin and homeostasis

• You have read that the skin can make vitamin D and that it protects the body from outside substances.

• Both of these functions help regulate the body’s internal environment.

the skin and homeostasis

• The skin also works with other body systems to maintain homeostasis.

• The skin and circulatory system help cool the body when it becomes overheated.

• The skin also works with the nervous system and muscular system to help the body react to stimuli.

the skin and homeostasis