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Blood Circulation

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Blood Composition. The following are components of blood - red blood cells, white blood cells, platelets and plasma (the liquid component). Red blood cells are the pinky white circles, the white blood cells are the big red blobs. Red blood cells do not have a nucleus because they do not divide and multiply Red blood cells are bi-concave, they are donut shaped. Red blood cells contain a pigment called haemoglobin which can react with oxygen to form the unstable compound, oxy-haemoglobin. Hb+4O2 =Hb08 (reversible). It is the reaction of haemoglobin to oxy-haemoglobin. The main components of the human circulatory system From left to middle to right. ...read more.


White Blood Cells Some white blood cells are phagocytes. These attack bacteria by engulfing them and ingesting them. This is called phagocytosis. Some whit blood cells are called lymphocytes. These produce antibodies to kill bacteria. They are chemical compounds which can fight infection. Phagocytes have nucleus's that are like sausages (lobed). Lymphocytes have big circular nucleae. Platelets are FRAGMENTS of cells which are involved in blood clotting. When an injury occurs, the platelets release chemicals which convert fibrinogen (soluble) to fibrin (insoluble). Fibrin is the substance that forms the main part of the cell. Arteries, Veins and Capillaries. Blood flows around the body enclosed within blood vessels. ...read more.


These structures pass close to all the major organs and tissues of the body and capillaries are widely spread so that every single cell in the body is in close proximity to a blood capillary. The capillaries are the site of exchange of materials, e.g. oxygen, carbon dioxide and useful products of digestion and waste products. Arteries Veins Walls are thicker and more elastic. Walls are thinner and less elastic. Valves not present. Valves present. Narrow lumen. Wide lumen. Round cross-section. Oval cross-section. Table and Differences between arteries and veins. Difference in function Carry blood away from the heart. Carry blood towards the heart. Carry oxygenated blood (except for the pulmonary). Carry deoxygenated blood (except for pulmonary). Blood flows rapidly under high pressure. Blood flows under low pressure. Blood flows in pulses. Blood flows smoothly. ...read more.

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