A pump (your heart) is useless without the rest of the plumbing, which in your body is called the cardiovascular system. Here’s a quick look at how it all fits together and functions.
The lungs: The lungs are composed of an intricate series of air sacs surrounded by a complex, highly branching network of blood vessels. Their sole purpose is to receive the deoxygenated blood from the heart, fill the red corpuscles full of fresh oxygen, and send them back to the heart for delivery to the body.
The red blood cells give off waste products such as carbon dioxide at the same time they take on oxygen; the lungs then expel the carbon dioxide. This low-pressure system facilitates the rapid flow and reoxygenation of enormous amounts of blood.
The arteries: As oxygenated blood returns to the left side of the heart, it is pumped out to the body through the aorta, the main artery of the body, and into the rest of the arterial system to feed the entire body with oxygenated blood. Although the heart exerts enough force to push oxygenated blood throughout the body, the arteries also have muscular walls that help push the blood along.
The force exerted against resistance of the artery walls creates a high-pressure system that is very elastic to allow the arteries to expand or contract to meet the needs of various organs and muscles. Your blood pressure reading results from measuring the pressure in these arteries when contracting and at rest.
The capillaries: The arterial system divides and redivides into a system of ever smaller branches to distribute nourishing blood to each individual cell, ultimately ending up in a network of microscopic vessels called capillaries, which deliver oxygenated blood to the working cells of every organ and muscle in the body.
The veins: After oxygen leaves the capillary system, the deoxygenated blood and waste products from the cells are carried back through the body in the veins. The veins ultimately come together in two very large veins, called the inferior vena cava (vee-nuh cay-vuh) and the superior vena cava.
The inferior vena cava drains blood from the lower part of the body and superior vena cava drains blood from the upper part of the body. These veins discharge blood into the right atrium of the heart to be pumped into the right ventricle and out to the lungs again to start the whole process over again.
The blood: Although blood is not considered part of the cardiovascular system, circulating blood to every cell of the body is the reason the cardiovascular system exists. This red fluid transports oxygen and fuel to the cells and removes waste products. It’s also the delivery vehicle for many specialized cells and biochemicals, including those that contribute to the development of heart disease.