Circulatory System

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Circulation
Red Cells (binary/octet-stream)
By Fatima Syeda

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Circulatory (binary/octet-stream)
The circulatory system
The circulatory system is your body's transport system. It: * carries nutrients and oxygen to the cells  * removes carbon dioxide from the cells, taking it to the lungs where it is exhaled * transports other waste products to where they can be disposed of * distributes heat around body

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Your circulatory system consists of your heart, blood vessels and blood. The heart is the engine room of the circulatory system. It pumps continuously to keep the blood moving through blood vessels.
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Circulatory System

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ARTERIES AND CAPILLARIES
There are three types of blood vessels in your body: *arteries *capillaries *veins Arteries carry blood away from the heart, when the heart beats, it pumps blood through the arteries under pressure, to be able to stand the pressure the walls of the arteries need to be tough and elastic. If an artery is cut, the blood will spurt out very quickly. All major arteries are protected deep in the body.
Capillaries extend through the body, arteries branch into smaller and smaller blood vessels. The finest of these blood vessels are called capillaries. Capillary walls are only one cell thick, this allows dissolved materials to pass through them.

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VEINS
Veins carry blood back to the heart. The pressure of the heartbeat is lost as the blood flows through the very narrow capillaries. Blood is pushed back up to the heart by the contraction of the muscles pressing against the veins. To make sure the blood flows in one direction there are valves along the veins. These valves open when blood is flowing towards the heart and close when the blood flows away from it.
Veins (binary/octet-stream)

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BRUISES
When you bump yourself hard, some of the tiny capillaries near the skin burst and the blood leaks out into the surrounding tissue. Immediately after, the blood leaks into the surrounding tissue, a red mark appears here.
Bruise (binary/octet-stream)

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The Heart
The heart is situated in the middle of your chest, behind the breast bone. The heart is made of cardiac muscle. This muscle does not get tired like the muscles of your legs and arms do. The circulatory system is referred to as a double system because there are two separate circuits through which blood flows. *in one circuit, blood flows from the heart to the body and back to the heart. This circuit carries nutrients and oxygen to the cells and carbon dioxide and waste away from the cell. *in the second circuit, blood flows from the heart to the lungs and back again. The blood that arrives at the lungs is known as deoxygenated blood. This is blood that has very little oxygen in it 

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