Diaphragm

Anatomy In anatomy, the diaphragm is a shelf of muscle extending across the bottom of the ribcage, providing the floor to the thoracic cavity and the ceiling to the abdominal cavity. It is critically important in respiration, helping to expel air from the lungs when elevated and to draw air into the lungs when depressed. A hiatal hernia is a tear in the diaphragm.

Mechanics A diaphragm is a sheet of a semi-flexible material, anchored at its periphery, and most often round in shape. It serves either as a barrier between two chambers, moving slightly up into one chamber or down into the other depending on differences in pressure, or as a device that vibrates when certain frequencies are somehow applied to it. In this last sense, the human eardrum is a diaphragm. Pressure-flush valves in urinals[?] work by means of an internal diaphragm.

A diaphragm is also a method of contraception.