Tuesday, April 17, 2012

The Human Circulatory System

         
 The human circulatory system functions to transport blood and oxygen from the lungs to the various tissues of the body. The organs involved in the circulation of blood in the body form the circulatory system. Heart and blood vessels are the most important parts of our circulatory system. Heart is a muscular organ and it weighs about 300 Grams. It works like a pump and sends blood through a network of blood vessels known as arteries to different parts of the body. The blood returns to the heart for purification through veins. In this way, blood reaches every cell in the body to provide it with food and oxygen and to carry way waste products.

            Our circulatory system is a fine network of arteries, arterioles, capillaries and veins.

Arteries and Veins:

Thecoronary arteries arise at the point of maximum blood pressure in the circulatory system. An artery is a large vessel that carries blood from the heart to the different parts of the body. It branches into the smaller arterioles which further divide into very small vessels called capillaries. Capillaries carry blood to the cells. Capillaries change to venal capillaries, venules and finally veins. Veins carry the blood back to the heart. Scientists guess there are about 100,000 kms of blood vessels in our bodies.

Circulation:

            Blood is pumped from the right ventricle of the heart into the pulmonary artery. This carries the blood into lungs, where it absorbs oxygen and releases carbon dioxide. The blood returns to the left auricle or atrium of the heart through the pulmonary vein. The left auricle pumps the oxygenated blood into the left ventricle of the heart which pumps it into the aorta. The aorta, being the largest artery, carries the blood to other arteries ad arterioles. The blood absorbs food when it passes near the small intestine. Waste from the cells is removing from the blood when it passes through the kidneys. After the blood passes thought he cells of the body, delivering food and oxygen and removing waste, it returns to the heart through the vena cave, the largest vein of the body. The impure blood enters the right auricle which returns it to the right ventricle. It is again pumped to the hangs to receive a fresh supply of oxygen to make another trip. In this way, this cycle goes on for ever.


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