Body processes

Pulmonary Circulation – Function, Task & Diseases

Pulmonary circulation

The pulmonary circulation , also known as the lesser blood circulation , is part of the human cardiovascular system . It regulates the transport of blood between the heart and the lungs and is used for gas exchange , ie the absorption of oxygen into the blood and the release of carbon dioxide into the air we breathe.

What is the pulmonary circulation?

The heart is the drive pump for the transport system of the human organism, the so-called blood circulation . Its function is to supply the organs and tissues with oxygen and nutrients and to remove metabolic products.

This transport system, also known as the cardiovascular system, is made up of two partial circuits: the large body circuit and the small pulmonary circuit. Both circuits are functionally coordinated in such a way that the used blood is first transported through the lungs for oxygenation before it returns to the various regions of the body.

The blood that feeds the pulmonary circulation comes from the right side of the heart. It is pumped through an arterial vascular system into the capillaries of the lungs, where oxygen is absorbed from the breathing air into the blood and at the same time carbon monoxide is released from the blood into the breathing air. This exchange of oxygen and carbon dioxide is called gas exchange. The blood, which is now oxygenated, is transported back via the pulmonary veins and ends in the left half of the heart, where the systemic circulation begins.

function & task

The used, i.e. low-oxygen, blood is returned to the right side of the heart via the two large vena cavae. From the atrium it flows into the right main chamber. This forms the starting point of the pulmonary circulation. The contraction of the heart muscle during the ejection phase pumps blood through the opening pulmonary valve into the large pulmonary trunk, which splits into the left and right pulmonary arteries. These lead to the right and left lung respectively. There, according to the anatomical structure of the lungs, they branch out into the so-called lung lobes and lung segments into ever finer arteries , up to and including arterioles, and finally open into the capillary vessels. Like a dense network, the capillaries surround the air-filled air sacs (alveoli) that attach to the ends of the bronchioles . 

During the process of respiration , gas exchange takes place between the alveolar air and the blood in the capillaries. The alveoli and capillaries are separated only by a thin, selectively permeable wall. On the one hand, carbon dioxide can therefore be released from the blood into the alveoli and exhaled by means of diffusion . On the other hand, the inhaled oxygen can be absorbed from the pulmonary alveoli into the blood.

The oxygen-rich blood is transported back to the heart via a venous system that runs between the individual lung segments. So-called venules , i.e. the smallest veins , first collect the blood from the capillaries and then unite to form ever larger veins, which ultimately lead to the large pulmonary vein. This leads the blood to the left atrium, from where it enters the left ventricle and is discharged to the periphery of the body via the systemic circulation.

The vascular system of the pulmonary circulation is called the vasa publica. Compared to the vessels that supply the lungs with oxygen themselves, the so-called vasa privata, it serves the entire organism by enabling gas exchange, i.e. the absorption of oxygen and the release of carbon dioxide.

Diseases & Ailments

The vital gas exchange during the pulmonary circulation can be disturbed by various clinical pictures that cause reduced oxygen saturation and an excess of carbonic acid in the blood. The undersupply of oxygen usually manifests itself in those affected by rapid fatigue , shortness of breath and shortness of breath through to dizziness and a bluish discoloration of the skin and lips. Even organ damage can be the result. The body therefore tries to counteract the acute deficiency with an increased breathing and heart rate . 

Pulmonary emphysema , a chronic disease of the lungs, is responsible for such a disruption in gas exchange . The respiratory flow is impeded because the inhaled air is backed up in the pulmonary alveoli. The reason for this lies in an irreversible enlargement of the alveoli through the enzymatic destruction of the dividing walls, which are used for gas exchange.

Pulmonary edema describes a condition in which water collects in the lungs. More specifically, fluid from the capillaries penetrates into the alveoli, which severely impairs gas exchange. Pulmonary edema can be caused by acute pump failure in the left side of the heart, renal insufficiency and severe allergic reactions, but also a dangerously low oxygen partial pressure in the ambient air at altitudes of around 3000 meters or more.

Other serious diseases that affect the vessels in the lungs are pulmonary hypertension and pulmonary embolism . Pulmonary hypertension, also known as pulmonary arterial hypertension, is characterized by chronically elevated pulmonary arterial pressure. This high blood pressure in the pulmonary artery can be attributed to narrowing of the blood vessels and the associated increased vascular resistance. The consequence is poor oxygen supply and an increased, compensating pumping capacity of the heart. Especially the right side of the heart, which can lead to right heart failure .

A pulmonary embolism refers to the blockage of a pulmonary artery by a body or foreign object, causing a pulmonary infarction with tissue damage. The extent of the damage depends on the size of the affected artery and can be life-threatening. The vascular blockage is usually caused by thrombi , ie small blood clots, from the leg or pelvic veins.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.