Essay by gilloHigh School, 11th gradeB+, June 2004

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The circulatory system consists of the heart, blood, veins, arteries, and capillaries. The heart is the main function for the circulatory system. Without the heart the body will not get the oxygen and other resources that blood provides. The blood travels to and from the heart through arteries, veins, capillaries. The structures of all of these are well suited for the functions they perform.

The artery is the first elastic tube that the heart pumps the blood through and around the body. The artery has three main layers, these layers are; the inner lining, the elastic and muscle layer, and the fibrous layer. All of these three layers are fairly large and making the artery very large in size. The structure of the artery is very well suited for its function because the artery is the closest tube to the heart therefore the tube has to be large in size because the blood pressure that comes out of the heart is very high.

The pressure is very high because the heart needs to give enough force so that the blood can travel around the body and back to the heart. This is another reason why the tube has got to be very elastic; the tube has got to be elastic because the blood pressure can be so high that it can burst the artery open causing a lot of damage to the body. Veins have a similar structure to the artery but are smaller.

Veins have the same structure as an artery (inner lining, elastic and muscle layer, fibrous layer). Veins are a lot smaller then that of an artery and are just as elastic as an artery, this is because the vein does not have to withstand as much blood pressure as the artery.