Large Intestine

The undigested food is moved by peristalsis from the small intestine and into the large intestine.

Water is absorbed back into the body in the colon, and what is left is stored in the rectum, the lower part of the large intestine, until we are ready to go to the toilet.

It then comes out of the rectum through the anus as faeces. This process is called egestion. Sometimes it is confused with excretion (which means removal of waste made by the body).

The large intestine contains many bacteria which are important because they can digest some substances that humans cannot digest, such as fibre, and reduce the chance of harmful bacteria causing disease.

This video sums up the journey of food as it passes through the digestive system. It’s exactly what Tanno and Iguda would have seen from the Microwidget. Remember though, Tanno and Iguda reversed back from the large intestine and were absorbed into the blood instead.

The large intestine is actually only about a quarter of the length of the small intestine.
Sometimes the undigested food can stay in the large intestine for up to 2 days!
The bacteria in the large intestine produce a gas!


Demonstration of peristalsis

You will need:
1) a tennis ball
2) an old pair of tights

A simple way of showing how peristalsis happens is to try and push the tennis ball through the old pair of tights. You could time yourself to see how quickly this could happen.

Try replacing the tennis ball with something softer. Does this affect the time to squeeze it through the tights? Does it demonstrate the importance of softening the food at the start of digestion?

Don’t get confused – this process is called ‘peristalsis’, not ‘peristennis’!!

You can go to the previous PostcardsFromTheBody secret pages by clicking the places below.

MouthStomachSmall Intestine
Photo of PostcardFromThe Mouth