When we are ready to take a breath, the muscle that sits under the lungs, called the diaphragm, contracts and moves downwards. This expands the lungs and pulls air into the body.
Muscles between the ribs called the intercostal muscles also move the rib cage outwards, to give the lungs more room to expand.
Air travels through the pharynx, larynx, and the trachea - and then to the bronchial tubes which lead to the lungs.
Breathing is controlled by our brain without us needing to think about it – on average, about 16 times per minute.
However, we can also consciously regulate our breathing if we choose, such as when singing or speaking.
The lungs are made up of sections called ‘lobes’. The right lung has three lobes, but the left lung only has two, to allow room for the heart.
Air is transported from the mouth through the windpipe, also called the trachea. The windpipe divides into two bronchial tubes so that air is distributed to each lung.
They divide further into brochioles, which end in tiny structures covered in a moist film, called alveoli. Alveoli are filled with capillaries, through which oxygen can moved from the lungs into the blood to be carried around the body.
Carbon dioxide moves from the blood into the lungs, and leaves the body with the next breath.
When oxygen has been absorbed into the body, we need to expel the used air with carbon dioxide in it, so that we can replace it with a fresh supply containing more oxygen. To breathe out, muscles between our ribs contract at the same time as the diaphragm muscle below the lungs relaxes and rises up. This squeezes the lungs, forcing air out - and we are ready to take another breath.
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