The digestive system Cambridge IGCSE Biology (9–1) revision
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In plain words
Your gut is a long tube from mouth to anus, about nine metres of it. Food goes in as lumps too big to be any use. By the time it has travelled the tube it has been broken into molecules small enough to pass into your blood, and what can't be used is passed out.
Three things to know
- In order: mouth, oesophagus, stomach, small intestine (duodenum, then ileum), large intestine (colon, then rectum), anus. The liver, gall bladder and pancreas add juices but food doesn't pass through them.
- Five stages: ingestion (taking food in), digestion (breaking it down), absorption (into the blood), assimilation (cells using it) and egestion (passing out what's left).
- Food is pushed along by waves of muscle contraction called peristalsis.
Tips and tricks
- Egestion is not excretion. Faeces are undigested food that never entered the body's cells.
- Know what each organ does in a few words: stomach churns and starts protein digestion; small intestine finishes digestion and absorbs; colon absorbs water.
It lands in your notebook with its questions as flashcards.
The digestive system: 5 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
Which organ does food not pass through?
The liver makes bile, which is added to the food.
What is peristalsis?
Muscles in the gut wall squeeze behind the food.
Where is most digested food absorbed?
Its lining is covered in villi, giving a huge surface area.
What is the main job of the colon?
What remains becomes faeces.
What is egestion?
It leaves through the anus.
Quiz
5 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 7 marks. Write your answers on paper, then check them.
The digestive system
Cambridge IGCSE Biology (9–1) 0970 · 7 marks · papermunch.org
Name ______________________________ Date ______________
List, in order, the parts of the alimentary canal that food passes through after the mouth.[3]
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Oesophagus, stomach, small intestine (duodenum then ileum), large intestine (colon then rectum), anus.
State the difference between absorption and assimilation.[2]
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Absorption is the movement of digested food molecules into the blood. Assimilation is the uptake and use of those molecules by the body's cells.
Describe how food is moved along the oesophagus.[2]
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By peristalsis: waves of contraction of the muscles in its wall push the food along.
Answers: The digestive system
- 1. Oesophagus, stomach, small intestine (duodenum then ileum), large intestine (colon then rectum), anus.
- 2. Absorption is the movement of digested food molecules into the blood. Assimilation is the uptake and use of those molecules by the body's cells.
- 3. By peristalsis: waves of contraction of the muscles in its wall push the food along.