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A diaphragm is some sort of separating membrane. This gives rise to several meanings:
Anatomy
A diagram of the thoracic muscles featuring the diaphragm
In the anatomy of mammals, the diaphragm is a shelf of muscle extending across the bottom of the ribcage. Its latin name is the transversus thoracis. It separates the thoracic cavity (with lung and heart) from the abdominal cavity (with liver, stomach, intestines, etc.). In relaxed state, the diaphragm is shaped like a dome. It is critically important in respiration: in order to draw air into the lungs, the diaphragm contracts, thus enlarging the thoracic cavity. (The muscles between the ribs also participate in this enlargement.) When the diaphragm relaxes, the air is pushed out by the elasticity of the lung and the tissues lining the thoracic cavity.
The diaphragm also helps to expel vomit, feces, and urine from the body and produces the pressure necessary for coughing and sneezing.
A hiccup occurs when the diaphragm contracts periodically without voluntary control.
A hiatal hernia is a tear in the diaphragm.
If the diaphragm is struck, or for other reasons, it may spasm briefly, making breathing difficult. This is called "being winded" or "having the wind knocked out of you". In some martial arts, practitioners are trained to do this.
There are three main apertures (or holes) in the diaphragm, one each for the inferior vena cava, aorta and oesophagus.
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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.
A diaphragm pump uses a diaphragm to pump a fluid. A typical design is to have air on one side constantly vary in pressure, with fluid on the other side. The increase and decrease in volume caused by the action of the diaphragm alternately forces fluid out the chamber and draws more fluid in from its source.
Acoustics and Biology
In a loudspeaker, a diaphragm is the thin, semi-rigid membrane attached to the central magnet. The magnet induces the diaphragm to vibrate, producing sound.
Using this in reverse converts air vibrations (sound) into electrical signals, as in the microphone. Similarly, the eardrum uses this same principle, using a diaphragm to stimulate nerves to transmit a neural "image" of sound to the brain.
de:Membran
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