Why does my tummy rumble?

I’m back with another great question this week, send in by Sarah, who wants to know …

Why does my tummy rumble?

It is all explained in this short video, just click to play (or, if you prefer, you can read the answer below).

While we sometimes find the noise a little embarrassing it is actually a really natural, and essential thing and shows that our bodies are working correctly, but why all the noise?

Let’s take a closer look!

The noises come from our digestive system, which is basically a long tube that stretches from out mouth to our anus! It usually comes from our stomach or small intestine.

The wall of this tube is mainly made up of muscles, called smooth muscles, which move in a certain way to push food through the system. This muscular movement is called peristalsis and this is how it works…

A small area of muscles contract, a bit like squeezing a ring around a part of the tube and this pushes things like foods, liquids and gases forward a little; then these muscles relax and the muscles in front of them contract and so on, pushing food and other content down the tube with each contraction.

Think about squeezing toothpaste from a tube!

The noises we hear are due to the movement of food, liquids and gases down the digestive tract. We associate the noise with an empty stomach, or being hungry, but the sounds are made when we have food in our system too. We often don’t notice them as the sound is dulled down.

When our digestive system is empty the noise is a lot louder.

It makes sense that peristalsis happens when we need to pass food through our digestive system, but why all the activity when our stomach is empty? Well this is the result of something called the Migrating Motor Complex or MMC for short!

This usually happens when our stomach and intestine have been empty for about two hours; a type of electrical pulse is triggered and this causes peristalsis through the digestive system. This serves a type of cleansing function; it clears any pockets of leftover food, mucus, bacteria and other debris from the stomach and small intestine.

The MMC response is usually triggered when our digestive system has been empty for about 2 hours

The MMC response is triggered every 90 to 120 minutes, until the next meal is eaten. It does tend to quieten down a bit while we sleep and then ramp up the activity again when we waken, which is why we often have gurgling tummies in the morning.

I hope you enjoyed this short explanation and video; Do let me know in the comments below and as always, if you have a question you’d like answered just leave it in the comments below! 


Science blogger and writer; Owner of Dr. How's Science Wows; Mother of three junior scientists who have taught me that to be a great scientist you need to look at life through the eyes of a child!

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