A Venn diagram has two intersecting circles, and the area in the center is what the two things being contrasted have in common. That said, a human lung will expand as the diaphragm, a sheet of muscle below the lungs pulls down. By doing so, the pressure outside the lungs becomes greater than inside due to the expanded size of the chest cavity and this pushes air into the lungs during inhalation. During exhalation, as the diaphragm moves back up, it causes the size of the chest cavity to decrease and the air pressure to become greater inside the lungs relative to outside. This causes the air to leave the lungs during exhalation. An old-fashioned mechanical fuel pump operates on the principle that a diaphragm is pulled downward creating a vaccuum which draws in fuel and when the diaphragm is pushed back up again, it expels the fuel out of an orifice. Both operate on a change in air pressure and both employ the use of a diaphragm. In your Venn diagram, the things they have in common go in the center of your two intersecting circles.