How Does Blood Circulate Through The Human Body?

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The Circulatory System

Blood moves through the body in a kind of circle. This circular movement contributes to the name, "circulatory" system. The intricate network, made up of miles of arteries, veins and capillaries that carry nearly 5 liters of blood, is a simple way to move oxygen and nutrients around the body. The circulatory system is made up of three components working together: the heart (coronary circulation), the lungs (pulmonary circulation) and the blood vessels (systemic circulation).

Coronary Circulation

Coronary circulation refers to the movement of blood through the heart. The heart muscle is the pump that pushes blood. The heart is made up of four chambers: the two upper chambers are called the atriums, and the the two lower chambers are called the ventricles. Waste-rich blood fills the right atrium, which then contracts and pushes the blood into the right ventricle. From the right ventricle, the blood is pumped into the lungs via the pulmonary artery. Thus begins the next section of the circulatory trip.

Pulmonary Circulation

When the waste-rich blood enters the lungs, it fills the lung capillaries. It is within these capillaries that the carbon dioxide in the blood is exchanged for oxygen. The new, oxygen-enriched blood continues its journey through the pulmonary veins in the lungs and returns to the heart through the left atrium. From the left atrium, the blood is pumped to the left ventricle and then leaves the heart by way of the aorta. Fortunately, valves keep the blood flowing in the proper direction, preventing any blood from flowing backward and causing problems. Once the blood has made its one-way journey through the left ventricle, it can move to the next step in circulation.

Systemic Circulation

When the oxygenated blood is pumped through the aorta, the blood continues on its circular trip through the body in systemic circulation. Now the blood is forced through the arteries, which forces the blood through smaller arteries called arterioles. The arterioles carry the blood and nutrients to the even smaller capillaries, where the blood makes contact with the cells in the body. Oxygen is delivered and waste cells are picked up to make the journey back to the heart. For the return trip, the waste-rich blood is pumped through the veins. Eventually, the veins reach the heart, where the waste-filled blood flows into the right atrium, and the circulatory journey starts all over again.