Pick one before you read on. It is fine to be wrong.
By the end you can
Trace food through the mouth, gullet, stomach and intestines
Explain why food must be broken into small pieces to be absorbed
Think of a meal of rice and beans. You chew it, swallow it, and feel nothing more. But your body works on it for many hours. Draw its path first.
Draw it first
Draw the path of food
1 Draw the mouth. Food goes in here.
2 Draw the gullet, a tube that leads down from the mouth to the stomach.
3 Draw the stomach, a bag where food is mixed and squeezed.
4 Draw the small intestine, a long tube in many coils.
5 Draw the large intestine round the coils. Waste leaves at the end.
Digestion is breaking food down into tiny pieces. The long tube that food goes through is called the gut. It starts at the mouth and ends where waste leaves the body.
In the mouth, your teeth cut and grind food. Saliva makes it wet and starts to break it down.
Incisors cut, canines tear and molars grind. Teeth break food into smaller pieces. This is the first step of digestion.
Next you swallow. Food goes down the gullet. Its muscles squeeze, in waves, and push the food along. That is why you can swallow even when you lie down.
The stomach is a stretchy bag. Its muscles squeeze the food and mix it with juices. The food turns into a thick liquid.
The small intestine is a very long, coiled tube. More juices break the food into the tiniest pieces here. These tiny pieces pass through the wall of the small intestine into the blood. We say the blood absorbs them.
This is a model. In it, the gaps are wider than the small pieces and narrower than the big ones. Only small pieces get through.
What is left goes into the large intestine. It takes back water. The rest leaves your body as waste.
Each part of the gut has one job.
See it three ways
With things
Pour rice grains and sugar water through a cloth into a cup. The sugar water goes through. The rice stays on top.
As a picture
In words
A cloth is a model of the gut wall. Only tiny pieces can pass through a cloth with tiny gaps. So food must be broken into tiny pieces before the blood can take it in.
Try it
A cloth for a gut wall
You need: a clean cloth, two cups, a spoon of rice, a spoon of sugar, water.
Be safe: Do not eat or drink the rice, the sugar water or anything from the cloth. Wash your hands afterwards.
Stir the sugar into half a cup of water until it has gone clear.
Hold the cloth tight over the empty cup. Pour the sugar water on to it. Watch what goes through.
Now pour the rice on to the cloth. Watch what happens.
What you will see: The sugar water goes through the cloth. The rice grains stay on top.
If you cannot try it, this is what happens.
A wrong idea many people have
Digestion happens only in the stomach.
Why it feels right: The stomach is big, and you can feel it fill when you eat.
The test that breaks it: Follow the picture of the gut. Food is chewed in the mouth and mixed in the stomach. Most of it is absorbed in the small intestine, which is longer than the rest.
What is true: Digestion starts in the mouth and goes on all along the gut. Most absorbing is done in the small intestine.
Key words
digestion
breaking food down into tiny pieces.
gullet
the tube that takes food from the mouth to the stomach.
small intestine
a long coiled tube where the tiny pieces pass into the blood.
absorb
to take in. The blood absorbs tiny pieces of food through the gut wall.
large intestine
the wide tube that takes back water and leaves the waste.
Back to your guess
The answer is B: It travels through a long tube and is broken into tiny pieces on the way.
Food travels through a long tube called the gut. On the way it is broken into tiny pieces, and the body takes in the useful ones.
Check yourself
Try each one before you look. A wrong answer tells you where to go next.
Which list shows the way food goes?
See the answer
Mouth, gullet, stomach, small intestine, large intestine
Food goes in at the mouth and down the gullet to the stomach. Then it goes through the small intestine and the large intestine.
If you chose B: The gullet comes before the stomach, and the small intestine comes before the large one. Check the picture of the gut. Go to S3.3.2.
If you chose C: Food is mixed in the stomach first. The small intestine comes after it. Go to S3.3.2.
What is the job of the gullet?
See the answer
It squeezes food down to the stomach
The gullet has muscles that squeeze in waves and push the food down to the stomach.
If you chose B: The gullet only carries food. Teeth, stomach and small intestine break it down. Go to S3.3.2.
If you chose C: Air goes down the windpipe. The gullet is a different tube, and it carries food. Go to S3.3.2.
In which part of the gut do most tiny pieces of food pass into the blood?
See the answer
The small intestine
The small intestine is long and coiled. Its wall lets tiny pieces of food through into the blood.
If you chose A: The stomach mixes and squeezes the food. Most absorbing is done further on. Go to S3.3.2.
If you chose C: The large intestine takes back water. The pieces of food were absorbed before this. Go to S3.3.2.
In the model of the gut wall, which pieces cannot pass through the gaps?
See the answer
The big pieces, because they are wider than the gaps
The gaps are narrower than a big piece, so it stays on top. A small piece is narrower than a gap, so it goes through.
If you chose B: Weight does not decide it. A heavy piece that is small enough would still pass. Width does. Go to S3.3.2.
If you chose C: The small pieces do pass through. They are narrower than the gaps. Go to S3.3.2.
Why must food be broken into small pieces?
See the answer
Only tiny pieces can pass through the gut wall into the blood
The gut wall acts like a wall with tiny gaps. Only very small pieces can get through it into the blood.
If you chose A: The stomach holds the same amount either way. The reason is in the wall of the small intestine. Go to S3.3.2.
If you chose B: Speed is not the reason. Big pieces would still not pass into the blood. Go to S3.3.2.
From an earlier chapter
Which system does the stomach belong to?
See the answer
The digestive system
The stomach and the intestines are organs of the digestive system.
If you chose A: The circulatory system moves blood. The stomach is in the system that handles food. Go to S3.3.1.
If you chose C: The nervous system sends signals. The stomach is in the system that handles food. Go to S3.3.1.
Keep it
Copy this into your exercise book.
Food goes mouth, gullet, stomach, small intestine, large intestine. It is broken into tiny pieces. Only tiny pieces pass through the gut wall into the blood.
Draw: Draw the gut as one long tube. Label the five parts and draw an arrow the way the food goes.
