General information
Pulmonary circulation (small circulation) is the transport of blood between the lungs and the heart. It serves to enrich the oxygen-poor blood from the right heart with oxygen and to transport the oxygen-rich blood back to the left heart. From there the oxygen-rich blood is pumped back into the body.
Although the pulmonary vessels contain a lot of oxygen, the lung needs its own vessels again to supply itself with oxygen. To distinguish between the two vascular circuits, the pulmonary vessels are called Vasa privata. The vessels that supply oxygen to the rest of the body are the vasa publica.
The function of the pulmonary circulation
The function of the pulmonary circulation is to transport blood between the heart and the lungs. It is used for gas exchange, i.e. the renewed absorption of oxygen into the blood and the release of carbon dioxide via the air we breathe. The gas exchange takes place in the alveoli (air sacs in the lungs).
During breathing, carbon dioxide (CO2) is released by diffusion and oxygen (O2) is absorbed from the alveolar air into the blood. In order for the oxygen to be transported in the blood, it is bound to the red blood pigment hemoglobin. The blood is now oxygen-rich (= oxygenated) and is transported back to the heart via a venous vascular system.
From there, the oxygen-rich blood is then transported via the so-called great body circulation to the remaining organs in the body. The vessels of the pulmonary circulation are called vasa publica, because they enable the exchange of gases and this serves the entire organism. In contrast, the vessels that supply the lungs themselves are called vasa privata.
This topic could also be of interest to you: The human blood circulationThe oxygen-poor blood from the body first reaches the right atrium of the heart via the two large vena cava (superior and inferior veins). During diastole, the tricuspid valve, which separates the right atrium and right ventricle, opens and the oxygen-depleted blood enters the right ventricle. During the expulsion phase of the heart (systole), the blood is drained via the large pulmonary trunk (truncus pulmonalis) into the vessels of the lung.
This large trunk divides into the right and left large pulmonary artery (arteria pulmonalis). This artery branches out in the respective lungs down to the smallest capillaries. It is in this capillary area of the pulmonary alveoli that gas exchange takes place.
The CO2 produced in the body is released from the blood and exhaled, while the oxygenated air is absorbed into the smallest bronchi during inhalation and can enter the blood through the alveoli. Now the oxygenated blood flows back to the heart in various pulmonary veins. In this way, the smallest veins join together to form ever larger veins, until finally the left and right large pulmonary veins (vena pulmonalis) open into the left atrium.
From there, the oxygen-rich blood reaches the left ventricle (left ventricle) via the mitral valve during diastole. During the expulsion phase of the heart (systole), the now oxygen-rich blood is pumped through the aortic valve into the aorta and thus into the major circulation of the body. Since the walls of the bronchi are too thick and the air flow velocity too high, the lungs need their own vessels to supply them.
The small branches of these vessels are called rami bronchiales. The bronchial rami of the left lung originate from the thoracic artery, while the vessels of the right lung also originate from the various vessels of the intercostal arteries. The venous outflow of these arteries reaches the azygos vein on the right side close to the hilus and the hemiazygos vein on the left side. The peripheral small veins (bronchial veins) open into the large pulmonary veins of the pubic vasa.
- Pulmonary circulation
- Vascularization of the lung
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