How your lungs work

About your lungs

Your lungs are incredible. Every day you take about 25,000 breaths, mostly without thinking.

How often you breathe in and out every minute depends on your age and what you’re doing. If you’re resting, an adult will breathe around 12-20 times a minute – that adds up to around 17,000 – 30,000 times a day! The amount of air that moves in and out of your lungs can vary from just a few litres a minute when you’re resting to over 100 litres a minute if you’re exercising vigorously.

The lungs absorb oxygen from the air you breathe in and transfer it into your bloodstream so that it can get to every part of your body. As the cells in your body work, they produce a waste gas called carbon dioxide that is released into the bloodstream. Your lungs get rid of this waste gas when you breathe out.

What are your lungs made up of and how do they work?

Diagram of the lungs Your two lungs fill your chest and sit on either side of your heart. The left lung is smaller than the right because it shares that side of the chest with your heart.

Your windpipe – also called your trachea - carries air into the lungs and out again when you breathe out. The windpipe divides into airways called bronchi. These branch into smaller and smaller airways. The smallest are too narrow to be seen with the naked eye. This is often called the bronchial tree. At the end of these tubes are tiny air sacs called alveoli. This is where gas exchange happens. Under a microscope, the inside of your lungs look like a giant sponge.

There are around 300 million air sacs and if they were spread out they would cover an area roughly the size of a tennis court.

What is the pleura?

The pleura is a thin, transparent membrane that surrounds your lungs, and lines the inside of your ribcage. It has two layers so the outside of the lungs can slide smoothly against the inside of the chest wall as you breathe.

What muscles do you use to breathe?

Your main breathing muscle is the diaphragm. This divides your chest from your abdomen.

Your diaphragm contracts when you breathe in, so pulling the lungs down, stretching and expanding them. It relaxes back – into a dome position – when you breathe out, reducing the amount of air in your lungs.

The abdominal muscles are used to push air out of the lungs when you breathe out.

There are also muscles in between the ribs, which keep the ribcage stiff and help with breathing. These are called intercostal muscles.

Next: Why do you breathe?>

Download our how your lungs work PDF (488KB)

Last medically reviewed: February 2018. Due for review: February 2021

This information uses the best available medical evidence and was produced with the support of people living with lung conditions. Find out how we produce our information. If you’d like to see our references get in touch.