AP BIOLOGY

Detailed explanation-1: -It should be thin( 1mm or less) to allow diffusion effectively. The respiratory surface must have a large surface area for maximum oxygen uptake in minimum time. It must be richly supplied with blood vessels for maximum oxygen uptake.

Detailed explanation-2: -The small round alveoli allow for an amazingly large surface area for this gas exchange to take place. Remember, the blood capillaries must be in contact with the respiratory surface for gas exchange to take place. Therefore, the greater the surface area, the more gas exchange can occur.

Detailed explanation-3: -A respiratory surface is covered with thin, moist epithelial cells that allow oxygen and carbon dioxide to exchange. Those gases can only cross cell membranes when they are dissolved in water or an aqueous solution, thus respiratory surfaces must be moist.

Detailed explanation-4: -Each alveolus is very closely associated with a network of capillaries containing deoxygenated blood from the pulmonary artery. The capillary and alveolar walls are very thin, allowing rapid exchange of gases by passive diffusion along concentration gradients.