What is the Cardiovascular System?
The cardiovascular system includes the heart and the blood vessels. The heart pumps blood, and the blood vessels deliver blood throughout the body.
Function of the Heart and Blood Vessels
Every cell in your body needs oxygen in order to live and function. The heart delivers oxygen-rich blood to every cell in the body. The arteries are the passageways through which the blood is delivered. The largest artery is the aorta, which branches off the heart and then divides into many smaller arteries. The veins carry the deoxygenated blood back to the lungs to pick up more oxygen, and then back to the heart once again. Blood flows continuously through the circulatory system, and the heart muscle is the pump that makes it all possible!
Your heart, just like all other muscles in the body, needs its own supply of oxygen in order to function properly. Although its chambers contain blood, the heart receives no nourishment from the blood inside the chambers. The heart gets its blood supply from the coronary arteries. The two major coronary arteries (the right coronary artery and the left main coronary artery) branch off the aorta, and then divide into many smaller arteries that lie in the heart muscle and feed the heart.
Arteries are thick-walled vessels that carry blood away from the heart to nourish all parts of the body. Arteries have a covering of elastic fibers that contain a layer of muscle that absorbs the tremendous pressure wave of a heartbeat and slows the blood down. This pressure wave can be felt in the arm and wrist - it is the pulse.
Arteries divide into smaller arterioles and then into even smaller capillaries, the smallest of all blood vessels. One arteriole can serve a hundred capillaries. Here, in every tissue of every organ, blood's work is done when it delivers nutrients and oxygen to each cell and takes away the waste products that they don't need.
Veins are formed by capillaries, which deliver deoxygenated blood back to the heart. Veins, unlike arteries, have thin walls because the blood has lost the pressure which forced it out of the heart, so the dark, reddish-blue blood which flows through the veins on its way to the lungs travels very slowly on its way to be reoxygenated.
Returning to the heart, the veins enter special vessels, called the pulmonary arteries located within the wall on the right side of the heart. The blood flows along the pulmonary arteries to the lungs to collect oxygen, then back to the heart's left side to begin its journey around the body again.