About your lungs - the structure of your lungs

All day, every day, your lungs work, often without you thinking about it. On this page, we explain what your lungs are made of, how they work and the muscles you use to breathe.

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?

Your two lungs fill your chest and sit on either side of your heart. Lungs are made up of areas called lobes – your right lung has three lobes, and your left lung has two. Your left lung is smaller than your 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 airways 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 in your lungs 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 covering, called a 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.

The space between the two layers is called the pleural space and it normally contains a small amount of fluid. This fluid lubricates the two surfaces and lets your lungs and chest wall move and expand as you breathe in and out.

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