The digestive system — Cambridge IGCSE Combined Science
The organs of the alimentary canal and the associated organs, the five processes of nutrition, physical digestion, stomach acid and bile.
Revision notes
3 short notes, in the order of the specification. Each one in short:
The alimentary canal is the long tube that food passes through from mouth to anus, while the salivary glands, pancreas, liver and gall bladder are associated organs that make and store digestive juices. The five processes of nutrition are ingestion, digestion, absorption, assimilation and egestion, the removal of undigested food as faeces.
Physical digestion breaks food into smaller pieces; incisors cut, canines tear, and premolars and molars crush and grind. Cambridge IGCSE Biology 7.3.
Stomach acid kills microorganisms and gives protease its optimum pH; bile emulsifies fats and neutralises acid so enzymes in the small intestine work.
Exam questions
3 exam-style questions (8 marks), each with its mark scheme.
Answer the questionsFlashcards
8 cards: flip them, mark what you knew, and practise the rest.
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The whole of human nutrition on one page, so you can see where this subtopic fits.
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Quick check questions
Name the process: the removal of undigested food as faeces.
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Egestion.
Supplement Give two functions of hydrochloric acid in the stomach.
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It kills harmful microorganisms in food and provides an acidic pH for optimum enzyme activity.
Written and checked against the Cambridge IGCSE Combined Science (0653) specification · Updated October 2026