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The circulatory system.

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Introduction

The circulatory system The circulatory system can be greatly affected by the type and amount of training a person does and therefore has to be considered very closely compared to other body systems. The main functions of the circulatory system are: * Transport- carrying blood, water, oxygen and nutrients throughout the body, and transport the removal of waste. * Body temperature control- the blood absorbs the body heat then carries it to the lungs and to the skin, where it is then released. * Protection- it helps to fight disease, e.g. antibodies, which fight infection, are carried in the blood and the clotting of seals cuts and wounds. The circulatory system has four main parts: * The heart * The blood vessels * The blood * The pulmonary and systemic circuits. ...read more.

Middle

There is an outer layer of tough fibrous tissue. The aorta is the largest artery in the body this divides into arterioles then into capillaries. Capillaries- These are so small they are only one cell thick, because of this they are semi-permeable and allow things to pass through the wall. Capillaries are found in clusters and feed the muscles and organs. At the end of the capillaries the blood flows into veins. Veins- The structures of veins are the same as arteries but they are smaller; the fibrous tissue and involuntary muscle is smaller. The veins pump blood back up to the heart; they have valves to stop the blood from flowing backwards. The skeletal pump also helps the blood in veins. Arteries near the veins push against them when a surge of blood goes through them, gravity assists veins above the heart, the action of breathing causes pressure changes and as the heart pumps, it also causes a sucking action that affects veins close to the heart. ...read more.

Conclusion

Plasma forms the remaining 55 per cent of the blood. This is the 'liquid section' and is mainly composed of water. It contains fibrinogen protein (which helps to clot), nutrients such as glucose and amino acids, waste products such as urea and some carbon dioxide and oxygen. The pulmonary and systemic circuits The pulmonary circuit carries deoxygenated blood through the heart to the lungs where it exchanges carbon dioxide for oxygen to become re-oxygenated. The pulmonary vein transports oxygenated blood to the left atrium of the heart. The systemic circuit carries oxygenated blood through the aorta from the left ventricle of the heart to all over the body, through capillaries. Having deposited most of the oxygen the blood flows back through the veins, into the right atrium through the vena cava. In this circuit the blood visits the cardiac muscle of the heart, the stomach, the intestines and liver, the muscles and skin. Oxygen transported through this system is vital for physical activity. Dayna Edwin 10GB 05/12/03 ...read more.

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This is a well researched and structured report.
1. The structure is good throughout, although the introduction subheading is missing.
2. The language used is strong throughout and includes some degree level terms.
3. The sources of researched information need to be included.
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Marked by teacher Luke Smithen 16/07/2013

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