Anatomy And Physiology

Anatomy Physiology

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The cardiovascular system consists of the heart and the various blood vessels which carry blood around the body. The role of the aorta and arteries is to carry oxygenated blood from the heart to the tissues and organs of the body. This is apart from the pulmonary arteries which carry deoxygenated blood from the heart to the lungs.

The heart is basically a pump which causes the blood to flow through the arteries. The aorta is the main artery and emerges from the left ventricle. The left ventricle being the main pumping chamber on the left side of the heart. The internal diameter of the aorta is approximately 1 inch as it emerges from the heart.

The aorta branches almost immediately, into the left and right coronary arteries. These two arteries and their branches supply blood to all parts of the heart. Once the coronary arteries have branched off, the aorta rises above the heart before arching downwards again.

It is from this arch that the two main arteries to the head and brain, the left and right carotid arteries emerge. The left and right subclavian arteries supplying each arm also branch off here. The arch then takes the aorta down to the chest and abdomen. Three main arteries supply the intestines and liver with blood and each kidney has its own artery. The aorta ends in the abdomen where it branches into the left and right iliac arteries - the arteries supplying the pelvis and legs.

Structurally the aorta and arteries are basically muscular tubes which must be strong enough to cope with the considerable pressure generated by the heart as it pumps the blood through them. The outer layer of an artery is a fibrous tissue sheath. This fibrous sheath surrounds a thick, muscular and elastic layer which gives the artery its strength. Rings of muscle about this elastic layer encircle the artery. The inside layer of the artery is known as the endothelium. The endothelium consists of a smooth layer of cells to help the blood flow as freely as possible.

The thick elastic walls of the bigger arteries play an important role in the circulation of the blood. Much of the force of each heartbeat is stored in these walls and then released in the pause between each heartbeat, further helping to push the blood forward along the artery.

The main arteries branch out to supply the extremities and organs with oxygen and food. As they branch their diameter diminishes until arteries become arterioles and then the blood enters the immense network of tiny blood vessels known as capillaries. It is in the capillaries that oxygen and food are released and waste products taken up. Capillaries are so small that blood cells must proceed in  single file along them.

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