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The Structure and Function Of Arteries, Veins and Capillaries.

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Introduction

Sarah English The Structure and Function Of Arteries, Veins and Capillaries In its route from the heart to the tissues, the blood passes through channels of six foremost types: elastic arteries, muscular arteries, arterioles, capillaries, venules and veins. I intend to explore the structure and function of arteries, veins and capillaries. When an artery branches into smaller and smaller vessels, eventually the blood vessel is too small to see with the naked eye. At that point, it is called an arteriole. Likewise, a venule is a microscopic vein. Arteries All arteries are comprised of three different layers but the proportion and structure of each varies with the size and function of the particular artery. A large artery, like the aorta, is comprised of the following layers, going from the inner to the most external layers: (1) The innermost narrow layer consists of a layer of endothelial cells separated from the inner layer by a thin layer of connective tissue that anchors the cells to the wall. ...read more.

Middle

Since it would be unworkable to get all the blood back to the heart as quickly as it left the heart (because there is no pumping mechanism to do so); veins have to be able to hold more blood than arteries. The veins provide a "storage area" for our blood, which is why the diameter of the veins is larger than the artery diameter. At any given time, the majority of our blood is within our veins. Veins have a thinner smooth muscle layer that allows for the expansion of the vessels and minimize resistance by reducing friction to the flow of blood. Because blood pressure is lower in veins, since the blood has had to travel some distance through the many capillaries, the diameter of muscle walls are needed to contain blood within the veins. Since the blood pressure is lower, the blood has to be pushed towards the heart via skeletal muscles and venous valves. ...read more.

Conclusion

From a functional point of view, the two most important parts of the circulatory system are the heart and capillaries. The heart is obviously important because it is responsible for pumping blood around the body. Capillaries represent the place where exchange of materials takes place, which is the principal function of the circulatory system. The structural differences between arteries and veins are all based in their relationship to the heart. Since arteries receive blood from the heart, the blood they receive is under a lot of pressure. At the same time, this pressure helps the blood move through the arteries- even when the arteries are opposing gravity (like the carotid artery running towards the head). In conclusion, the arteries carry oxygenated blood away from the heart, and due to the high pressure of this blood the arteries have thick wall, which contain many muscle fibres. The veins carry deoxygenated blood to the heart and because blood is of a lower pressure, have thinner walls consisting of less muscle fibres. Capillaries are the principal part of the circulatory system; they allow substance exchange. ...read more.

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