The Heart and Blood Circulation Essay

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The Heart and Blood Circulation The heart is a four chambered muscular pump around the size of a fist. It beats about 100,000 times a day pumping around 2,000 gallons of blood through about 100,000 miles of organic tubing.

The heart is a big muscle with four valves connected together to make a two-stage pump. The heart gets its energy by oxidizing blood sugars. This released energy, contracts the heart’s many muscle cells, and the four chambers squeeze blood out into the arteries.

The arteries are thick walled muscular tubes which carry blood away from the heart. The heart has two sides - the left ventricle and the right ventricle. The artery from the right ventricle pumps blood to
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The venae cavae collects oxygen depleted blood from the body and routes the blood to the right atrium in the heart. When the right atrium squeezes, it pushes blood through the tricuspid valve into the right ventricle. Like the other three heart valves this is a one way valve (blood can only flow in one direction). When the right ventricle contracts, it pushes blood through the pulmonary valve and on into the lungs. Because it does not take much pressure to get blood to the lungs and back, the right side is smaller than the left. The left side has to work harder pumping blood to the rest of the body. Blood in our arteries is at a high pressure, blood in our veins is at low pressure. The blood, rich in oxygen, returns from the lungs through the pulmonary veins into the left atrium. To get all the way round blood has to go through the heart twice and this is why it is called a double circulation.

Blood contains red blood cells, white blood cells and platelets floating in a liquid called plasma. The red blood cells contain haemoglobin and carry oxygen. Haemoglobin is a protein which becomes oxyhaemoglobin in the lungs. The white blood cells fight disease by making antibodies and fighting germs.

Blood transports these vital materials around the body. Blood plasma contains nutrients, hormones and waste products. Oxygen is carried
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