Why Is the Left Lung Smaller? 6 Questions About Breathing
We breathe around twenty thousand times a day, yet we rarely stop to wonder how the process works. Here are the answers to six of the most-searched questions about breathing, from the shape of the lungs to why it is possible to pass out without feeling short of breath.
Are the left and right lungs the same?
No. The left lung is smaller because it has to make room for the heart. The right lung has three lobes, while the left has only two.
The left lung also has a notch called the cardiac notch, where the tip of the heart rests. The right lung, on the other hand, is shorter, because the liver pushes the diaphragm up on that side. Even so, overall, the right lung is the larger of the two.
Do we breathe through both nostrils at the same time?
Yes, but almost never equally. It is normal for one nostril to be clearer than the other, even without a cold. This phenomenon is called the nasal cycle, and it was described by the German physician Richard Kayser in 1895.
The turbinates on one side swell with blood while those on the other side shrink. Every few hours, the sides switch. The most widely cited hypothesis is that this lets one side's mucous membrane rest and rehydrate while the other does the work.
Why can we see our breath when it's cold?
The air leaving the lungs is at about 34 degrees and almost saturated with water vapour. When it meets freezing air, it cools suddenly and that vapour condenses into tiny droplets.
It is the same process that creates the cloud rising from a pot when you lift the lid. What we see is not vapour, which is invisible, but liquid water: a tiny cloud.
Is what we breathe oxygen?
Only partly. Dry air is made up of 78% nitrogen, 21% oxygen and almost 1% argon. Nitrogen goes in and out of the lungs without the body using it.
On top of that, we use little of the oxygen. The air we exhale at rest still contains around 16%. That is why mouth-to-mouth resuscitation works: the air blown in can still oxygenate another person.
Is the Amazon the lungs of the planet?
During the 2019 fires, the idea spread that the Amazon produces 20% of the world's oxygen. It even appeared in a tweet by Emmanuel Macron. However, it is false.
Its net oxygen contribution is roughly zero. The rainforest consumes almost all the oxygen it produces: it is used up by its trees, its animals and the microbes that break down the leaf litter.
Why do we feel like we're suffocating when we hold our breath?
It is not due to a lack of oxygen, but to an excess of carbon dioxide. Sensors in the medulla oblongata detect the acidity caused by CO₂ as it builds up. A lack of oxygen barely triggers the alarm until it becomes severe.
That is why hyperventilating before free diving is dangerous: it flushes out CO₂, the alarm is delayed and you can pass out without warning. For the same reason, a room filled with nitrogen can kill without any sensation of suffocation, because CO₂ is still being exhaled normally.
Frequently asked questions
Why is one nostril more blocked than the other?
Because of the nasal cycle: the turbinates on one side swell with blood while those on the other side shrink, and every few hours they switch.
How much oxygen is left in the air we exhale?
At rest, exhaled air still contains around 16% oxygen. That is why mouth-to-mouth resuscitation can oxygenate another person.
Is it dangerous to hyperventilate before diving?
Yes. Hyperventilating flushes out CO₂, the signal to breathe is delayed and you can pass out without warning.
How many times do we breathe a day?
Around twenty thousand times, and almost none of those breaths are triggered by oxygen, but by the build-up of carbon dioxide.
Informative article written with the help of AI tools from the verified script of the video. The video is in Spanish.