What blood vessels surround the aveoli?

Alveoli are surrounded by a dense network of capillaries. These capillaries, which are derived from the pulmonary arteries, carry deoxygenated blood to the alveoli. The exchange of oxygen and carbon dioxide between the alveoli and the capillaries takes place through the thin walls of the alveoli. The alveolar capillaries then drain into the pulmonary veins, which carry oxygenated blood back to the heart.