How do people breathe by atmospheric pressure?

When people inhale, the volume of the lungs increases, and the pressure in the lungs decreases, which is smaller than the external atmospheric pressure.

So air enters the lungs from the outside.

When exhaling, the lung volume decreases and the pressure is greater than the outside, so the air is discharged from the lung.

In addition, because PT/V=K (P is pressure T, temperature V, and volume K is constant), there are volume decreases, pressure increases, volume increases, and pressure decreases.