The alveolar membrane is the gas exchange surface where carbon dioxide rich blood is pumped from the rest of the body in the alveolar blood vessels. Through the process of diffusion it releases its’ carbon dioxide and absorbs oxygen.

The alveolar ducts are tiny ducts that connect the respiratory bronchioles to the alveolar sacs, each of which contain many alveoli (like little balls). They are tiny end ducts of the branching airways that fill the lungs. Each lung holds about 1.5 to 2 million of them.

The tubules divide into two or three of the alveolar sacs at the distal end and distal terminations of alveolar ducts are atria (any chamber-like entrance to an organ) which then end in the alveolar sacs. respiratory bronchioles exist proximal to the alveolar ducts. Respiratory bronchioles feed into alveolar ducts which are formed by a serie of alveoli lying adjacent to one another. These ducts eventually terminate in groups or clusters of alveoli which are called alveolar sacs.

Respiratory Tree Branches:

• Respiratory Bronchiole

• Alveolar Duct; at atria

• Alveolar sac

• Alveolus air sac (plural alveoli or air sacs)

Alveolus, derived from a Latin term meaning “little cavity” is an anatomical structure that has the form of a hollow cavity. Alveolar sacs are the terminal end of this respiratory branch where exchange of carbon dioxide for oxygen takes place. Respiration is the process of gas exchange (breathing in oxygen and breathing out carbon dioxide); cellular respiration is where cellular breathing takes place to sustain life.