Lung Function and Anatomy: the Basics

Our lungs serve as vehicles that keep us alive, propelling us through life by facilitating the exchange of life-giving oxygen and carbon dioxide with the air that surrounds us. How does their structure promote their function?

Our lungs are pyramidal organs that come in a pair, connected to our trachea–or windpipe–by our right and left bronchi, which bring air to and from the lungs. At the base, our lungs are bordered by our diaphragm, which is a flat muscle shaped like a dome that separates the thoracic and abdominal cavities and contracts and relaxes as we breathe. Interestingly enough, although they’re a pair, our lungs are asymmetrical: our right lung is shorter and wider than the left, the latter of which occupies a smaller volume. There is an indentation on the surface of the left lung known as the cardiac notch; this area creates space for the heart.

The lung’s apex is known as the superior region, while the base is by the diaphragm and the costal surface borders our ribcage. Each lung is divvied up into separate units known as lobes, which are separated by fissures. The right lung is split into three lobes: the superior, middle and inferior, while the left and less voluminous lung is split into two: the superior and inferior.

In our lungs, every lobe is separated into multiple bronchopulmonary segments, each receiving blood from its own artery and air from its own tertiary bronchus. Our bronchi branch into smaller bronchioles, creating subdivisions of the lobes called pulmonary lobules. And each pulmonary lobule has its own large bronchiole with multiple branches. Every lobule is separated from one another by a wall of connective tissue called an interlobular septum.

The blood in our lungs facilitates oxygen and carbon dioxide gas exchange, an essential bodily function. We need oxygen to carry out practically everything we do, and we create carbon dioxide as a waste byproduct. And it’s our lungs that are responsible for ridding our bodies of the carbon dioxide and getting our bodies the oxygen it needs. The pulmonary artery carries deoxygenated blood to the alveoli, which are miniscule air sacs in our lungs that allow quick gas exchange. As the pulmonary artery follows our bronchi, it branches over and over again, becoming increasingly smaller. And as the pulmonary arteries become closer to the alveoli, they become the pulmonary capillary network, which is made up of thin-walled, tiny vessels that mirror the bronchioles and alveoli structure.

The respiratory membrane is formed where the capillary and alveolar walls meet; here, blood becomes oxygenated. Afterwards, newly oxygen-enriched blood is drained from the alveoli through the pulmonary veins and exits the lungs, and is then transported throughout the body, carrying oxygen to the places it needs to go and allowing us to function properly.

It’s quite beautiful to see how form and function are so deeply intertwined in our bodies, working together in harmony to create a living, breathing organism capable of so much.