eli5 Why do our stomachs move when we breathe?
In: Biology
If you increase the volume of a box containing gas without changing the amount of gas, it spreads over more space, and this decreases pressure. If you open the box then, air from the outside rushes in as it has higher pressure, and then the two pressures equilibrate. We follow that principle to breathe, we expand the volume of the lungs by flexing the diaphragm, which then draws air into the lungs. The diaphragm is an umbrella shaped muscle, with the dome protruding into our throax, when we flex it, it flattens, the dome is gone, so the thorax volume increases and the abdominal cavity volume decreases a bit. We can also employ other mechanisms especially for faster or deeper active breathing like pulling out ribcage out and up (if you have rings on top of each other with a pole connecting them on one side, then the circles would drop on the other side due to gravity, if you pull them back up, the cylinder they make has more volume, the circles are our ribs and the pole is our spine).
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