A stretchy bag
Your stomach sits high in your belly, a bit to the left, under your ribs. It's shaped like the letter J.
When it's empty, it's small and wrinkly inside. When you eat, it stretches like a balloon. A grown-up's stomach can comfortably hold about 1 to 1.5 liters, that's about 4 to 6 cups.
As your stomach stretches, it sends messages to your brain, so you can feel when you're full.
Churning and mixing
Your stomach has three layers of muscle that squeeze in different directions. They churn and mash food, like a washing machine.
At the same time, the stomach lining makes gastric juice. This juice has a strong acid and helpers called enzymes (EN-zymes) that start breaking food into smaller and smaller pieces.
After about 2 to 4 hours, your meal has turned into a thick, soupy mix called chyme (KIME). A ring of muscle at the bottom lets it into the small intestine a little at a time.
Big, rich meals take longer, and drinks pass through faster.
Strong acid, safe lining
Stomach acid is very strong. It helps break down food, and it kills many of the germs that sneak in with what you eat.
So why doesn't your stomach digest itself? Its lining makes a thick layer of slimy mucus that coats the inside, like a raincoat.
Your stomach also makes a fresh inside lining every few days, so it stays healthy.
Growls and burps
Your tummy growls when its muscles squeeze air and liquid around inside. It can happen anytime, but it's louder when your stomach is empty, because there's no food to muffle the sound.
That rumble has a science name: borborygmi (bor-buh-RIG-mee). Try saying that three times fast!
When you eat or drink, you swallow some air too. A burp lets extra air out of your stomach. Fizzy drinks make more burps because they're full of gas bubbles.
Butterflies in your stomach
Your stomach and your brain talk to each other all the time. When you feel nervous or excited, your tummy might feel fluttery, like it's full of butterflies.
That's normal. A few slow, deep breaths can help calm both your brain and your tummy.