At the end of the bronchial tree lie the alveolar ducts, the alveolar sacs and the alveolar, which consist primarily of simple squamous epithelium that permits rapid diffusion of oxygen and carbon dioxide.
- Alveolar ducts connect the respiratory bronchioles to the alveolar sacs
- Alveolar sac is the name given to the alveoli that develop together into bunches, each bunch grouped together is called an alveolar sac
- Alveoli are cup-shaped with thin walls. They are surrounded by a network of blood vessels called capillaries that also have thin walls.
It is between the two membranous walls of the alveoli and the capillaries that the exchange of gasses between the air in the lungs and the bold in the capillaries occurs.