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Physiology and anatomy of the cardiovascular system

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The cardiovascular system includes the blood, the heart and the arteries, capillaries and veins. The main part of this system which I will concentrate on is the heart, blood vessels and the blood. The heart is a muscular pump with a resting rate of around 70 beats per minute. It beats without nervous stimulation but any changes in the heart rate depend on the nerves and some hormones. Anatomy of the Heart Function of the Heart The hearts main job is to pump the blood all around the body so everywhere has a constant supply to keep it in good working order. The heart muscles contract and relax regularly without any nervous stimulation and seems to be able to go on forever without getting tired, this may be due to the fact that for much of a heart beat the muscle is actually relaxing. ...read more.


Veins carry blood back to the heart (except in hepatic portal vein). This is the major artery of the three as it has a relatively large inner diameter and also contains valves. Capillaries are the smallest of the three blood vessels. They do not contain valves and have the inner diameter of about one red blood cell. Capillaries carry blood through organs and tissues. Contents/Function of the Blood The blood is the red liquid which gets transported all around the body and is a complex mixture of substances; all of them do different jobs. In the blood there is a mixture of white blood cells, red blood cells, platelets and plasma. There is about 55% of plasma in the blood, 45% of red blood cells and only 1% of white cells and platelets. ...read more.


Red blood cells are shaped like a disc and are dished on each surface; this shape is called the biconcave disc. This shape also makes it easier for the cell to bend and fold as they pass through the smallest blood vessels. Worn out red cells are removed in the liver or spleen and replaced by new ones from the bone marrow. The life span of a red blood cell is about 100-120 days. Platelets are much smaller than the red blood cells and vary in shape; they also help the blood to clot. They are produced in the bone marrow again and are created by 'budding off' from special cells. Plasma is a clear, pale yellow liquid that is 90% water. The remaining 10% contains many substances including glucose, amino acids, fats, calcium, urea, carbon dioxide, antibodies (which destroy microbes) and also hormones which control the way the body works. ...read more.

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