Logan Upston, of Balclutha Primary School, asks :-

Why does my tummy grumble?

Gil Barbezat, a gastroenterologist at the Otago Medical School, responded.

Everyone's tummy rumbles sometimes. To know why rumbling happens we need to know how the tummy works.

The tummy is part of the digestive system. This is made up of a long, long tube (the gut) which starts at the mouth and has a few bulges along the way. The bulges in this long tube are to slow the food and drink down, and to mix and process what we have eaten.

The tube has a number of layers. Each layer has a special job to do. Some layers are made up of muscle which helps squeeze and squelch the food along. The layers that line the inside of the tube add special juices, like a `sprinkler system' to the food. People take in about 1.5 to 2 litres of food and drink every day. About another 6 to 8 litres of fluid is added through this `sprinkler system'. This helps makes the food into a mixture like soup. Air, mostly swallowed with the food, and some gasses that are formed from the processing of the food also make their way down the gut with the food.

The parts of food which nourish the body are sucked out of the tube into the blood through many highly specialised little `drains'. When that is gone, only about 200 ml. is left. This forms the poo.

Knowing this makes it easier to understand why your tummy rumbles. The mixing of the food and juices and gas starts at the upper end of the gut (in the stomach). As the food is processed, it is squeezed into the next part of the tube (the small intestine). This goes on all the way down the gut until it reaches the lower end. Long rumbles happen with a long squeeze, pushing the food along. It is the mixing, squeezing, squelching and movement of food, fluid and gas which makes the rumbling sounds.