What happens when you get the air knocked out of you?

Question

Why can't you breath when you take a hard fall or whatever, and you get the air knocked out of you? I'm loking for an antomy/physiology answer... is it a muscle thing o a nerve thing or a mix or something else entirely?

I asked this in one of my classes a few months ago, and for the life of me, i cannot remember the answer... :(

Answer 1

The way I understand it, it means that the air is suddenly pushed out of the lungs.

Answer 2

When there is a sudden force applied to the abdomen or back it can cause large and sudden difference in pressure across the diaphragm.  The Diaphragm then over-stretches and the nerves stretch with it, resulting in a spasm of the diaphragm which makes it hard to breathe for a few moments.

The effect seems to be minimized if air has been exhaled at the time of the blow.