How Do Lungs Work? Lung Structure and Function

Evolution of lungs

When creatures first wriggled out of the sea and onto dry land, they were gifted with a crucial adaptation: primitive lungs. These lungs were not the efficient air bags that we have today. They were a loose collection of blood vessels that were originally created to absorb tiny bits of oxygen from water running across them.

When early amphibious creatures began to spend more time on land, the crude network of blood vessels and tubes eventually evolved into a tightly woven mesh that more closely resembled the lung structures that allow humans to absorb oxygen from the air instead of water.

How do lungs work?

When you take a breath, air moves past the main tube (called the trachea) and branches into the two smaller bronchi tubes. The brochi shuttle air into the right and left lung lobes and from there, the air is sent into the network of tiny bronchiole tubes that resemble slender noodles. As you inhale, your chest and tiny tubes have expanded to compensate for the increased pressure and the air is forced to move into tiny sacks called alveoli. The alveoli are the microscopic meatballs in this somewhat silly pasta analogy and take on the most important role for your entire respiratory system: the exchange of oxygen and carbon dioxide.

One key feature of the alveoli is that they are packed with tiny air tubes and also enmeshed in a dense tangle of thin blood vessels. The thinnest blood vessels surround each alveoli air sac cluster and as the blood rushes past the alveoli air tubes, it release the excess carbon dioxide and absorbs oxygen molecules before being pumped back into your heart to be distributed to the rest of your body.