Blood and Circulation Essay

2866 WordsFeb 4, 201312 Pages
Blood and circulation The heart requires its own constant blood supply in order to keep beating and this is delivered through the coronary arteries. Genetic and lifestyle factors can lead to the coronary arteries becoming blocked, and an increased risk of heart disease. All living cells need to be supplied with materials like oxygen and glucose. They also need to get rid of waste materials like carbon dioxide. In single-celled organisms these materials are able to just diffuse in and out of the cell, however multicellular organisms e.g. humans are much larger, and therefore diffusion through all the cells would be too slow. Animals need a blood circulatory system to transport materials efficiently around the body. In a circulatory system the heart acts as a muscular pump to keep the blood moving. The heart contracts, pushing blood around the body. Blood flows away from the heart along the arteries, through capillaries (which are tiny blood vessels that are close to the body’s cells) at the organs and then back to the heart through the veins. As blood travels round the body through blood vessels it loses pressure, therefore the arteries have the highest pressure and veins have the lowest. Animals with gills e.g. fish have a single circulatory system, meaning one circuit of blood vessels from the heart. This system needs a two-chambered heart; one chamber to receive blood, and one to pump blood out to the gills and to the rest of the organisms’ body. In a single circulatory system, the blood loses pressure as it’s pumped to the gills and them the rest of the body. This means that the overall pressure of the blood is fairly low. The single circulatory system enables the process of gas exchange. The blood from the body is brought by the veins into the heart; then the heart pumps this deoxygenated blood toward the gills. In the gills the blood become oxygenated and

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