Steps of Digestion
Biology: Cambridge International GCSE Supplement, topic 7.2.3
Digestion
There are 6 steps in the process of digestion:
Ingestion
- Food and drink is taken into the body.
- Ingestion happens in the mouth.
Physical digestion
- Food is broken down into smaller pieces using force.
- Physical digestion is done by teeth in the mouth, by the stomach contracting and by bile (a substance made in the liver, stored in the gall bladder and secreted into the duodenum).
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Chemical digestion
- Food is broken down into smaller, soluble (can dissolve) molecules by digestive enzymes.
- Enzymes are secreted by the salivary glands, stomach, pancreas and small intestine.
Absorption
- Absorption involves the movement of small food molecules and ions through the wall of the intestine into the blood.
- Absorption of soluble food molecules happens in the ileum of the small intestine.
- Absorption of water happens in the small intestine.
Assimilation
- Assimilation is the movement of digested food molecules into the cells of the body where they are used, becoming part of cells.
- Assimilation happens in all body cells, or in any body cell that needs it.
Egestion
- Egestion is the passing out of food that has not been digested or absorbed, as faeces.
- Egestion happens in the rectum and anus.
Test yourself on Steps of Digestion
Which process follows assimilation during digestion?