THE SKINSection 3

SKIN ~ THE BIGGEST ORGAN

SKIN STRUCTURE

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New cells are produced at the base of the epidermis

EPIDERMISOuter layerThinnest layerCells are deadCells are water repellant

Thousands of cells rub off when you shake hands, scratch your ear, etc.

MELANINCells in epidermis produce a chemical called melanin.

Melanin is a pigment that protects your skin from UV rays and gives it colour.

The more melanin you have, the darker you are.

As you exposed to UV rays, melanin production increases and your skin becomes darker.

Lighter skin have less protection to sun’s rays. It will burn more easily and may be more susceptible to skin cancer.

DERMISLayer of skin directly below the epidermis

Thicker than epidermis

Contains many blood vessels, nerves, muscles, oil and sweat glands

DERMIS (D)

DERMIS (D)

FATTY LAYER - SUBCUTANEOUS LAYERBelow the dermis is a fatty region that helps to insulate the body.

This is where most of the fat goes when a person gains weight.

FUNCTION OF SKINProtectionSensory responseFormation of vitamin DRegulation of body temperatureRidding the body of wastes

Most important….PROTECTION

PROTECTIONSkin keeps out the bad bacteriaGlands (in skin) secrete fluids that can damage or destroy some bacteria

Skin slows down water loss from body tissueSpecial nerve cells detect and relay information to the brain. These cells help you feel the softness of fur and the coarseness of sandpaper.

VITAMIN DSmall amounts of vitamin D are produced, in the presence of UV light, from a fatlike cell in the epidermis.

Vitamin D helps the body absorb calcium into your blood stream from food in your digestive tract.

LET’S STAY WARMThe skin regulates body temperature using blood vessels.

Blood vessel dilates and allows more blood to flow through. This also allows thermal energy to be released.

dilate

BLOOD VESSELS IN SKIN

Blood vessel constrict and allow less blood to flow through. This also allows thermal energy to be stored.

constrict

BLOOD VESSELS IN SKIN

After running After being in the cold

constricted or dilated?

SWEAT GLANDSAn adult has about 3 million sweat glands!

They help regulate your temperature and eliminate water, salt and other waste products.

BRUISESTiny blood vessels under the skin have burst. Red blood cells leak into the tissue. The blood cells break down and release hemoglobin. From the outside of your skin it looks black and blue.

Phagocytes come in to clean up the debris. They engulf the red blood cells and break them down.

As the hemoglobin breaks down, it changes colours to green and yellow and then brownish.

CUTSAny tear in the skin.Blood flows out of the cut until a clot is formed.

A scab forms and keeps bacteria from entering the body.

Cells in the surrounding blood vessels fight infection while the skin cells beneath the scab grow to fill the gap in the skin.

Scab then falls off and leaving the skin behind.

TOO MUCH DAMAGESometimes not enough skin cells are left that can divide to replace this lost layer.

This can lead to rapid water loss from skin and muscle tissues, then to infection and possible death.

SKIN GRAFTSPieces of skin that are removed from one part of a person’s body and moved to the injured area.

It is kept alive by nearly blood vessels and soon becomes part of the surround skin.