3. Alveoli Copyright o The McGraw-Hill Companies, Inc. P Left pulmonary artery Left main bronchus bronchia a Branch of Smooth muscle Respiratory Each of the clustered alveoli includes an abundance of pulmonary capillaries, thereby assuring that the ventilated air is brought into close proximity to the"pulmonary blood, allowing efficient and thorough gas exchange between the air and the blood.Each of the clustered alveoli includes an abundance of pulmonary capillaries, thereby assuring that the ventilated air is brought into close proximity to the “pulmonary” blood, allowing efficient and thorough gas exchange between the air and the blood. 3. Alveoli