The Circulatory System Essay

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The Circulatory System

The circulatory system in anatomy and physiology is the course taken by the blood through the arteries, capillaries, and veins and back to the heart. In humans and the higher vertebrates, the heart is made up of four chambers the right and left auricles, or atria, and the right and left ventricles. The right side of the heart pumps oxygen-poor blood from the cells of the body back to the lungs for new oxygen; the left side of the heart receives blood rich in oxygen from the lungs and pumps it through the arteries to the various parts of the body. Circulation begins early in fetal life. It is estimated that a given portion of the blood completes its course of circulation in
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The veins, in turn, unite with each other to form larger veins until the blood is finally collected into the superior and inferior venae cavae from which it goes to the heart, completing the circuit.

In addition to the pulmonary and systemic circulations described above, a subsidiary to the venous system exists, known as portal circulation. A certain amount of blood from the intestine is collected into the portal vein and carried to the liver. There it enters into the open spaces called sinusoids, where it comes into direct contact with the liver cells. In the liver important changes occur in the blood, which is carrying the products of the digestion of food recently absorbed through the intestinal capillaries. The blood is collected a second time into veins, where it again joins the general circulation through the right auricle. In its passage through other organs, the blood is further modified. Coronary circulation is the means by which the heart tissues themselves are supplied with nutrients and oxygen and are freed of wastes. Just beyond the semilunar valves, two coronary arteries branch from the aorta. These then break up into an elaborate capillary network in the heart muscle and valve tissue.
Blood from the coronary capillary circulation enters several small veins, which then enter directly into the right auricle without first passing into the vena cava. The action
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