How does the stomach work in space? Do astronauts feel constant need to throw up since the contents are bouncing around inside?
In: Biology
Think of the stomach like a muscular water balloon with two ends being held shut. The ends are held shut with muscles like your butt hole called sphincters. When it’s empty, it’s “deflated,” and when you fill it, it expands to hold the solids or liquids you put in it. If you were to hang upside down on earth, the upper sphincter keeps the stuff in. Just like in space, the sphincters hold it all in. During digestion, the stomach muscles expand and contract to squish and mix the stuff inside. When it’s broken down the foods enough, the lower sphincter opens and the stomach muscles squeeze the stuff out to move it along to the next stage of digestion, like letting go of the end of a water ballon, it will squeeze it all out. Think of squishing and shaking a water balloon. There’s not much open space in your stomach, unless you ingest a lot of gas, for stuff to “bounce around,” and your stomach contents are always being squished and mixed. Though gravity can help, digestion doesn’t rely on it to work. The muscular action the body uses to move liquids and solids through it is called peristalsis and is why we can eat,l and drink while upside down or laying down.
If you did feel like vomiting in space, it would likely be an issue called space sickness, which is a form of motion sickness where your visual system and your vestibular system tell your brain two different things about your motion. But that’s another ELI5
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