Pulmonary circulation

Pulmonary circulation is the portion of the cardiovascular system which carries deoxygenated blood away from the heart, to the lungs, and returns oxygenated (oxygen-rich) blood back to the heart. The term pulmonary circulation is readily paired and contrasted with the systemic circulation. A separate system known as the bronchial circulation supplies blood to the tissue of the larger airways of the lung.

Pulmonary circulation is the movement of blood from the heart, to the lungs, and back to the heart again. Deoxygenated blood leaves the heart, goes to the lungs, and then re-enters the heart; Deoxygenated blood leaves through the right ventricle through the pulmonary artery. From the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle. Blood is then pumped from the right ventricle through the pulmonary valve and into the pulmonary trunk of the pulmonary artery.

From the right ventricle, blood is pumped through the pulmonary semi-lunar valve into the left and right pulmonary arteries (one for each lung) and travels through the lungs.

The pulmonary arteries carry deoxygenated blood to the lungs, where carbon dioxide is released and oxygen is picked up during respiration. Arteries are further divided into very fine capillaries which are extremely thin-walled. Their function is to assist in the carrying of blood to all cells of the body. The pulmonary vein returns oxygenated blood to the left atrium of the heart.

The oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. This blood then enters the left atrium, which pumps it through the bicuspid valve, also called the mitral or left atrioventricular valve, into the left ventricle. From the left ventricle the blood passes through the aortic valve to the aorta. The blood is then distributed to the body through the systemic circulation before returning again to the pulmonary circulation.

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