AP BIOLOGY

Detailed explanation-1: -Alveoli have thin walls and a close network of blood arteries to allow gas exchange between blood and air-filled alveoli. They have a balloon-like structure to maximize surface area in exchange for gas.

Detailed explanation-2: -Each alveolus is cup-shaped with very thin walls. It’s surrounded by networks of blood vessels called capillaries that also have thin walls. The oxygen you breathe in diffuses through the alveoli and the capillaries into the blood.

Detailed explanation-3: -The alveoli present in the lungs have thin walls composed only of a single layer of cells in order to minimize the diffusion distance. Their walls are moist which helps the gases to diffuse better. They are richly supplied with blood capillaries to ensure the efficient exchange of gases with the bloodstream.

Detailed explanation-4: -The alveoli are surrounded by tiny blood vessels, called capillaries. The alveoli and capillaries both have very thin walls, which allow the oxygen to pass from the alveoli to the blood. The capillaries then connect to larger blood vessels, called veins, which bring the oxygenated blood from the lungs to the heart.

Detailed explanation-5: -Furthermore, the alveolar walls must be very thin so that they can change shape to allow gas to enter them on inspiration.