Two Circulations, One Vital Organ
Today I am looking at the bloody supply to our lungs
The lungs have a unique dual blood supply. One circulation makes gas exchange possible, while the other nourishes the lung tissue itself. Together, they keep oxygen moving into the bloodstream and carbon dioxide moving out.
Deoxygenated blood leaves the right ventricle through the pulmonary trunk, which divides into the right and left pulmonary arteries. These arteries follow the branching airways and form capillary networks around the alveoli. Across the thin alveolar–capillary membrane, carbon dioxide diffuses from the blood into the air spaces, while oxygen diffuses into the blood. Oxygenated blood then returns to the left atrium through the pulmonary veins.
The bronchial arteries arise from the systemic circulation, usually from the thoracic aorta or nearby branches. They deliver oxygenated blood to the bronchi, connective tissue, visceral pleura and supporting structures of the lungs. Some bronchial venous blood drains through the bronchial veins, while some enters the pulmonary veins, creating a small normal contribution to the physiological shunt.
The pulmonary circulation is a low-pressure, high-flow system designed for efficient gas exchange. The bronchial circulation operates at systemic pressure and supports the metabolic needs of the lung tissue. Connections between the two systems can provide some backup blood flow, but they can also become clinically important in conditions involving inflammation, obstruction or bleeding.
Let’s look at what happens if there is a blockage a blockage in a pulmonary artery, most often caused by a blood clot that has travelled from a deep vein in the leg or pelvis, is called a pulmonary embolism. It reduces or stops blood flow to part of the lung, so that area may still receive air but cannot exchange gases effectively with the blood. This can lower oxygen levels, increase pressure on the right side of the heart and, if the blockage is large or there are multiple clots, cause haemodynamic collapse or death. Possible symptoms include sudden shortness of breath, chest pain that may worsen with breathing, a rapid heart rate, coughing up blood, dizziness or fainting. A suspected pulmonary embolism requires urgent medical assessment.
Very interesting!