Re: Nostrils: a definition

Phil Nicholls (
Fri, 28 Jul 1995 02:03:56 GMT


>Ralph L Holloway ( sez:
>`On 23 Jul 1995, Colin Campbell wrote:

>`> I guess this explains the tragic results of the manned space program's
>`> long record of zero-gravity asphyxiations...
>` No, not at all, Colin. What it explains is that in addition to being
>`descended from aquatic apes, we are also decended from the the space
>`program of several million years some more irrelevant info for
>`us? R. Holloway.

>Nevertheless, he is correct. The only place gravity really comes in
>to play in breathing is on exhalation, where the weight of the
>chest can be sufficient to deflate the lungs, but there are
>muscles to assist that action, which is why we can breath in
>a weightless environment.

No. The diaphragm contracts, flattening out and decreasing air
pressure in the thorax. Air enters the lungs because the air pressure
outside is higher than that inside the lungs. When the diaphragm
relaxes it curves up into the chest, decreasing the volume of the
thorax and increasing air pressure.

In space (and aircraft) the cabin is pressurized.

When you climb a mountain or visit high altitudes, you have trouble
breathing. It's not because the air is "thin". The air pressure is
less, so you don't have as much force pushing it into your lungs.