Alveolar Ducts: Function & Definition

Instructor: Adrianne Baron

Adrianne has taught high school and college biology and has a master's degree in cancer biology.

This lesson will describe what alveolar ducts are and their location within the respiratory system. The function of alveolar ducts, and why they are necessary, will also be discussed.

The Respiratory System

Inhale and Exhale
Picture of rock art that says

Have you ever been panicked about an event or anxious about something that was going to happen? What was something that someone may have told you to do? S/he may have said something along the lines of, take a deep breath in, hold it, and exhale. That's because breathing helps to bring about relaxation and increases cognitive abilities among other things.

The system that allowed you to breathe, to relax, and think, is the respiratory system. The respiratory system, also called the respiratory tract, is the tract of organs that allows the intake of oxygen and output of carbon dioxide. The respiratory tract includes the nose and mouth, pharynx, larynx, trachea, bronchial tubes, alveoli, and lungs.

The Respiratory Tract
Diagram of respiratory tract

The respiratory tract goes from being a single tube to branching out into many tiny tubules at the location of the lungs. As a matter-of-fact, the bronchi get smaller and become bronchioles. This branching into smaller tubules requires sections to connect the parts of the tract.

What Are Alveolar Ducts?

One section that connects the tract is the alveolar duct. There are numerous alveolar ducts in the respiratory system that connect the alveolar sacs to the bronchioles. The alveolar sacs are exactly what they sound like. They are sacs of many alveoli, which are the cells that exchange oxygen and carbon dioxide in the lungs.

Since there are many alveolar sacs, this means that there are many alveolar ducts. In fact, there are estimated to be around 2 million alveolar ducts located in the lungs! So what exactly are all of these alveolar ducts doing for the respiratory tract?

Alveolar Duct Function

Alveolar Ducts Connect the Bronchioles to the Alveolar Sacs
Diagram of alveoli and alveolar ducts

The alveolar ducts assist the alveoli in their function. Alveoli are extremely tiny and therefore can only handle gas exchange when air arrives there at a certain pressure, and in a certain amount. The alveolar ducts collect the air that has been inhaled and transported through the tract and disperse it to the alveoli, in the alveolar sac that they feed into.

After gas has been exchanged by the alveoli, then the alveolar ducts collect the carbon dioxide that needs to be exhaled. Collecting the carbon dioxide from the many alveoli into the alveolar ducts allows the air pressure in the lungs to change and helps more air to be exhaled at one time.

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