Pathway of air Please help me with this question.

Alveoli bronchioles bronchi larynx epiglottis pharynx oral cavity or nasal cavity.

The alveoli are surrounded by a network of pulmonary capillaries.  These capillaries are made of simple squamous epithelium, therefore there are only two cells between the air in the alveoli and the blood in the pulmonary capillaries which permits efficient diffusion of gases.  It is through the moist walls of both the alveoli and the capillaries that rapid exchange of CO2 and O2 occurs.

Carbon dioxide diffuses from the red blood cells through the capillary walls, into the alveoli.  CO2 leaves the alveoli, exhaled through the nose and mouth. The opposite process occurs with O2, which diffuses from the alveoli into the capillaries, and from there into the red blood cells.

Each alveolus is lined with a thin layer of tissue fluid, which is essential for the diffusion of gases, because a gas must dissolve in a liquid in order to enter or leave a cell.  This is called the “earthworm principle”.  An earthworm will breathe through it's moist skin and suffocate if it's skin dries out.

The inner walls of the alveoli are covered with a lipid material known as surfactant. This surfactant helps to stabilize the alveoli preventing their collapse.  Absence of surfactant would be similar to a plastic bag that is wet on the inside.  It's walls would stick together and not allow for complete expansion.