How is the blood in the lungs enriched with oxygen

How does the cycle work?

The bloodstream supplies all cells in the body with nutrients and oxygen. It consists of the heart and the blood vessels that run throughout the body. The blood flows away from the heart in the arteries; the veins return it to the heart. The system of blood vessels resembles a tree: from the “trunk”, the main artery (aorta), there are thick arterial branches that branch out further and further. The smallest arteries end in a network of tiny blood vessels called the capillary network.

Humans have not just one but two blood circulation systems connected in series: organs, tissues and cells are supplied with blood and supplied with oxygen and other vital substances with the large body circulation. In the small pulmonary circulation, the fresh oxygen that flows into the body with the air you breathe reaches the blood. At the same time, the blood gives off carbon dioxide here.

The cycle begins with the relaxation phase of the heart between two heartbeats: then blood flows from both atria into the heart chambers. In the subsequent ejection phase, both heart chambers pump blood into the large arteries.

In the great circulation, the left ventricle pumps blood into the main artery (aorta). From the aorta, oxygen-rich blood reaches the capillary network via larger and smaller arteries. There the blood releases oxygen, nutrients and other important substances and absorbs carbon dioxide and waste materials. The now oxygen-poor blood is collected in the veins and reaches the right ventricle via the right atrium.

Now the small cycle begins: the right ventricle pumps the oxygen-poor blood into the pulmonary artery, which divides into ever smaller arteries and capillaries. The capillaries span the grape-shaped widenings at the end of the airways like a fine network. Here the blood gives off carbon dioxide and takes in fresh oxygen. Carbon dioxide is exhaled with the air we breathe, while the oxygen-rich blood flows through the pulmonary veins and the left atrium into the left ventricle. With the next heartbeat, the body's circulation begins again.