What is the oxygenated blood

Body and pulmonary circulation: Pathways and functions of blood circulation

It is vital that the blood flow and not stand still. It transports the oxygen from the air we breathe in to all cells in the human body. This flow of blood through the arteries, capillaries and veins is driven by the heart's pumping function. One vascular system allows blood to circulate through the lungs for gas exchange, while the other blood vessels supply the rest of the body.

1. Two systems can be distinguished in the circulation: pulmonary and body circulation

In the pulmonary circulation, also known as the small circulation, the blood flows between the heart and the lungs. It transports the deoxygenated blood to the lungs so that it releases carbon dioxide and absorbs oxygen. The oxygenated blood flows back to the heart. In the great circulation, the blood flows between the heart and the rest of the body. It transports the oxygen-rich blood to the cells and leads the oxygen-depleted blood back to the heart.

2. The motor for both cycles is the heart

The heart pumps the oxygen-rich blood from the left ventricle into the aorta, where it begins its way through the body's circulation. After the blood has supplied all the body cells with oxygen and nutrients, it returns to the right atrium with a low level of oxygen. From there, the deoxygenated blood shoots into the right ventricle. The heart pumps the blood from the right ventricle into the pulmonary arteries, where it enters the small circulation. The blood flows through the lungs, exchanges the carbon dioxide for the oxygen and returns to the left atrium. The oxygen-rich blood now shoots from the left atrium into the left chamber below, in order to flow again through the body's circulation.

3. The body and pulmonary circulation work hand in hand

The body and pulmonary circulation work hand in hand to supply oxygen to the body and remove the carbon dioxide. The pulmonary circulation facilitates the process of external breathing: the oxygen-poor blood flows into the lungs. It absorbs the oxygen from the tiny alveoli and releases the carbon dioxide to be excreted to them. The body's circulation supports internal breathing: the oxygen-rich blood flows into the capillaries throughout the body. The oxygen diffuses from the blood into the cells and the carbon dioxide from the cells into the blood.

4. The small or pulmonary circulation only transports blood between the heart and lungs

In the pulmonary circulation, the deoxygenated blood leaves the right ventricle and flows through the pulmonary trunk. The pulmonary trunk forks into the left and right pulmonary arteries. These arteries carry the deoxygenated blood to the arterioles and the capillary bed of the two lungs. Here the carbon dioxide is released and the oxygen is absorbed. The oxygen-rich blood flows from the capillary bed through the venules into the pulmonary veins. The pulmonary veins carry the blood further into the left atrium. The pulmonary arteries are the only arteries in which oxygen-poor blood flows, while the pulmonary veins are the only veins in which oxygen-rich blood flows.

5. The body's circulation supplies the entire body

In the great or body circuit, the oxygen-rich blood is pumped from the left ventricle into the larger body artery, the aorta. The blood flows from the aorta through ever smaller arteries into the arterioles and ultimately into the capillary bed that supplies the body tissues. There the oxygen and nutrients are released and the carbon dioxide and other end products of metabolism are absorbed by the blood. The oxygen-poor blood flows from the capillary bed through the venules into the body veins. The body veins open into the upper or lower vena cava (v. Cava superior / inferior), the largest vein in the human body. The two vena cava collect the deoxygenated blood and lead it to the right atrium.