Did you just have a snack? Maybe you had an apple or a cookie. You probably aren't thinking about what is happening to the snack, but your stomach is taking part in something similar to a science experiment — and this experiment happens all the time! In this activity, you will learn about how living things take in materials through the digestive system.

Your digestive system is involved in the ingestion and absorption of materials that are necessary for you to survive.

There are four steps in the digestive process: ingestion, digestion, absorption, and elimination. Let's take a look at the steps materials go through as they pass through your body.

Your mouth is the beginning of the digestive system. It is where you take food into your body. This is called ingestion.

Every time you eat something, saliva or spit forms in your mouth. With the help of your teeth, this helps to break food into smaller parts and make it mushy so it is easier to swallow. Your tongue helps in this process by pushing the food around in your mouth so that it can be chewed into smaller pieces and come into contact with as much saliva as possible. When the food is ready to be swallowed, the tongue pushes it toward your throat and into the esophagus, which is the second part of your digestive tract.

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The esophagus is about 25 centimetres long. It is like a stretchy pipe that goes from your mouth to your stomach. When the food has entered the esophagus, it does not just fall into the stomach. The esophagus is lined with muscles that contract and push the food along to the stomach. From the time you swallow, food takes about three seconds to reach the stomach. If you swallow too much at once, your throat hurts. This is the esophagus being stretched too much.

The small intestine breaks food into even smaller bits so it can be absorbed by the body. It does this with the help of the liver, pancreas, and gallbladder. These three organs send various fluids to help break down the food, and they also allow the body to absorb the nutrients from the food. Your food may spend up to 4 hours in the small intestine. In that time, most of it is absorbed into your body, but some goes into the large intestine.