Respiratory exchange surfaces of the lungs receive deoxygenated blood from which blood vessels?

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The blood that undergoes gas exchange at the respiratory surfaces in the lungs comes through the pulmonary arteries. These arteries carry deoxygenated blood from the right ventricle into the lungs, where it flows through the alveolar capillaries so oxygen can diffuse in and carbon dioxide can diffuse out. After this exchange, the blood returns to the heart as oxygenated blood via the pulmonary veins.

Bronchial arteries do supply oxygenated blood to the lung tissue itself, but not to the alveolar surfaces where gas exchange occurs, so they aren’t the source of blood for the respiratory exchange surfaces. The aorta is a systemic artery delivering blood to the body’s tissues, not the lungs’ gas-exchange beds. The pulmonary veins carry oxygenated blood away from the lungs, not deoxygenated blood to the alveoli.