Eli5 How does food and liquids remain inside the stomach and not “leak out of your mouth” whilst being in space?

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Eli5 How does food and liquids remain inside the stomach and not “leak out of your mouth” whilst being in space?

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Your esophagus is a muscle and can restrict itself, effectively closing your mouth off from your stomach. Same reason nothing will come out if you were to be held upside down.

There is a muscle at the top of your stomach. It is a ring that holds closed unless you are swallowing or puking. This is why you can be upside down and won’t have what’s in your stomach pour out. Same thing as why you don’t pee yourself each time you stand as there is one right at the exit of your bladder. These types of muscles are all through the body and control the flow of liquids.

Short answer? Sphincters.

Your stomach has muscles around the opening to keep food inside. Thus why you aren’t vomiting stomach acid when performing a hand stand or otherwise upside-down. Furthermore, muscles around your esophagus will actively push food down towards the stomach in a process called peristalsis, allowing you to properly swallow and eat regardless of orientation or if floating around in space.

All good answers and just reaffirming this is not a dumb question, humans and other mammals have a series of “valves” and muscles that keep pushing the food actively from the mouth to the butt.

Birds, for example, don’t. They need gravity to swallow and do the work. Hence why we sent monkeys, apes, and dogs into space to test early space ships and not smaller, easier, or cheaper animals.