How are humans able to fart gas out downwards if gasses naturally rise in the body?

The human digestive system is blocked off at several points by several sphincters. This prevents too-early passage of food as well as back-draft from gases. Since most of the gases build up in the final stretch, called the large intestine (which way shorter than the small intestine, but a bit wider), it simply becomes a matter of pressure build-up within a closed container. Once the pressure inside is bigger than the air pressure outside, any opening of the outside sphincter causes the gases to be expelled until pressure equalizes.

Physics does, but engineering overrides it. If the Alimentary tract was a hollow tube going vertically from top to bottom this might be true. But it goes back and forth and is also 'tight' in the way it sits inside your body, so food matter/faeces cant slosh around according to physics. The end product has to be moved by muscles in the wall of the intestine which squeezes it along, it doesnt move freely. So, if you stood up while a speculum was inserted and your anus opened up, only perhaps poo in the very last inches of your rectum might fall out, the rest would still need to be pushed out. Now, Gases can squeeze around far easier that faeces can, so when you far the gas pressure in your gut easily squeezes out of the tiny hole, it only takes a small amount of opening for the gas to exit. Hence the noise, similar to a balloon.

Get some sausage skin, hold it vertically, put in some sausage meat into the top, the meat doesnt easily fall out of the end cos the skin holds it into place. Now squeeze from the top of the sausage, thats what the gut is (broadly speaking) like. Now, cook and eat sausage.

[removed]

[removed]

[removed]

[removed]

[removed]