How does the diaphragm function in breathing?

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During inhalation the diaphragm muscle contracts and this causes it to (effectively) move downwards, its previously upwardly curving shape becomes a flatter one, and this decreases the pressure in the thorax region (the region in which the lungs reside) because there is more air space. As a consequence, air rushes in from outside the body, via the nose and mouth, and fills the lungs with air. The alveoli in the lungs takes the air and sends it round the blood-stream.
Exhaling is, obviously, the opposite: The diaphragm relaxes, moves upwards to it's original, relaxed state, and thus increases the air pressure in the thorax area (because there is now less air space), this forces air that was not removed by the alveoli, and air that has returned to the lungs from the blood-stream, back into the atmosphere via the nose and mouth. Also, in and out of your nose ...air goes in and out

The diaphragm provides the main force for breathing.(other muscles are used during exercise, like the scalenes and the intercostals) When the diaphragm contracts it moves down into the abdomen by doing so it increases the volume of the thoracic cavity which in turn creates a negative pressure(compared to atmospheric) on the lungs(it actually creates a negative pressure in the intraplueral space). This negative pressure creates a pressure differential between the lungs and the atmosphere causing air to come into the lungs. During exhalation the diaphragm relaxes and the elastic force of the lung causes the air to be pushed outwards.

First answer by Dappy but Happy. Last edit by ID0000000000. Question popularity: 21 [recommend question].