Your Lungs Are Actually Pretty Hairy

The human lungs are truly remarkable. There they sit, safely encased in their ribcage armor, tirelessly keeping billions of us breathing. It's quite the job, and we don't even breathe manually most of the time (unless we're thinking about it, which we are now).

As How Stuff Works reports, the average for a healthy pair of lungs is approximately 23,000 breaths per day. It's a full-time job, that's for certain, and the lungs are far more formidable than you may think. Per the American Lung Association, the passages of air that run through them are so numerous that they'd stretch for the distance from Las Vegas to Chicago.

As astonishingly vast and powerful as the human respiratory system is, though, it's far from infallible. The Office of Disease Prevention and Health Promotion stated in 2020 that, in the United States alone, 25 million people had asthma. Those who are particularly wary of their lungs might not appreciate the revelation that they are, in fact, full of hair.

Hairs that sweep the lungs clean

Hair, you might think, has no place in the breathing process. The idea conjures up either images of violent sneezes or of unsightly nasal hair. Surprisingly, though, the lungs contain a fine coating of tiny hairs, and they have a crucial role to play.

As Live Science reports, the trachea leads into the lungs and through the bronchial tubes, a network of tiny passageways that spreads through each lungs for the transport of air. The concern is that other tiny intruders like dirt and dust could find their way down there in the very same way.

Our brilliant bodies are ready for such dangers, however. The bronchial tubes, Live Science goes on, have a rather gross but very important, hairy lining. The minuscule hairs are known as cilia. Delightful mucus proceeds through the system through the movement of the cilia, removing tiny particles that could be harmful as it goes. Try not to dwell on these mental images too much, they're a little unsettling.

The importance of the cilia

In the paper "Cilia Dysfunction In Lung Disease" (via the National Library of Medicine), Ann E. Tilley et al point out that cilia are not hairs in the strictest sense. Rather, they are "evolutionarily conserved hair-like cellular organelles that project from the cell surface."

Nonetheless, they have a job to do, and they seem serious about performing it. Tilley et al go on to state that, "In the healthy human lung, cilia beat at 12 to 15 Hz in coordinated waves of metachronal motion that propel mucus cephalad at 4 to 20 mm/min." Every day, it seems, each of us swallows around 30 ml of this mucus. Smoking, the report goes on, can result in shorter cilia, a loss of them, and reduced capacity for regeneration of the hairy helpers.

Cilia that do not move in this fashion, or primary cilia, "were long thought to be vestigial remnants of motile cilia," according to Hiroaki Ishikawa and Wallace F. Marshall's "Methods in Enzymology" via Science Direct. Instead, it seems, they are found all over the body, and have crucial roles in our cells.