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The Cardiovascular System

The cardiovascular system is comprised of the heart, the lungs, as well as the veins and arteries within the body. In humans the function of the cardiovascular system is to oxygenate the blood and make sure that this blood travels to every living corner of the body. It also distributes nutrients that are picked out from the food you eat by the digestive system. It also carries the white blood cells called neutrophils and macrophages that hunt down and fight bacterial and fungal infections.

A diagram of the cardiovascular system

The heart is a muscle about the size of a clenched fist. It can be thought of as two separate pumps. The first pump pushes blood through the pulmonary artery to the lungs, where the red blood cells draw oxygen brought there through respiration (breathing). Having absorbed the oxygen and expelled carbon dioxide (which it picks up later in the cycle), the blood is forced through the pulmonary vein from the lungs and back into the heart.

From the left side of the heart (it looks like the right side in the diagram, because it represents a person facing the reader) it is pushed through the aorta and disbursed throughout the entire body. As it goes out, it travels through a system of arteries and capillaries bringing oxygen to the living cells (which in turn they use in the ATP-ADP cycle to create energy).

The red blood cells then pick up the carbon dioxide which is a byproduct of the ATP-ADP cycle. Other waste products also enter the blood stream (to be cleansed by the liver and kidneys). The blood then flows through a system of veins, eventually through the vena cava, and back to the right side of the heart to begin the process all over again. Note that blood vessels leading away from the heart are usually called arteries and those leading back to the heart are referred to as veins.

All kinds of things can go wrong with this system, including high-blood pressure and blockage of the blood vessels. Yet the heart is a remarkable muscle (called an involuntary muscle because it is not consciously controlled by the brain). If properly taken care of through good exercise such as frequent walking and good diet, it can serve a body for many years.

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