School โบ Digestion โบ Ages 10โ11
The digestive system
The organs of the digestive system and what each one does: chewing and saliva, stomach acid, bile and pancreatic juice, villi in the small intestine and water absorption in the large intestine. With a fair test on chewing and surface area.
Read
The digestive tract runs from the mouth through the oesophagus, stomach, small intestine and large intestine to the anus. Muscles move food along by squeezing in waves: peristalsis.[1]
In the mouth, teeth break food into smaller pieces. Saliva moistens it and contains an enzyme that begins to break down starch.[2][1]
The stomach is extremely acidic (pH 1.5โ2.5). Its enzyme pepsin starts digesting protein, and the food becomes a soupy mix called chyme.[2]
The liver makes bile, which helps digest fats; the gallbladder stores it. The pancreas makes a juice with enzymes that break down carbohydrates, fats and proteins.[1]
The small intestine is about 3 metres long in a living person. Its wall is covered in tiny finger-like villi, which give a huge surface through which digested nutrients pass into the blood.[3][2][1]
The large intestine absorbs water and turns waste into stool. Bacteria living there help break down leftovers and make vitamin K.[1]
Try it: Does chewing make a difference?
You need
- Sugar cubes (all the same brand and size)
- Three clear cups
- A measuring jug
- Water at room temperature
- A spoon and a saucer for crushing
- Stopwatch
Safety
Do not eat or taste the sugar. Use room-temperature water, not hot water. Wipe up spills so nobody slips.
What to do
- Put the same amount of water (for example 100 ml) at the same temperature into three cups.
- Prepare three sugar cubes: leave one whole, break one into 4 pieces, and crush one into small grains with the back of a spoon (this is 'chewing').
- Add each one to its own cup at the same time and stir each in the same way (for example, one stir every 10 seconds).
- Time how long it takes until you can see no sugar left.
- Repeat the test twice more and work out the mean time for each.
What happens, and why?
Crushed sugar dissolves fastest because breaking it into smaller pieces gives it a much bigger surface for the water to work on. Chewing does the same for food: teeth break it into smaller particles, so digestive juices and enzymes have more surface to act on. Bile does a similar job for fat, breaking it into small droplets.[2][4]
Play: Which organ?
Read each job. Which part of the digestive system does it? Pick the right box.
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Quiz
Other ages: Ages 6โ7 ยท Ages 15โ16