Explain mouth, oesophagus and stomach functions
Connect entry, transport, mixing and gastric digestion.
Section B7.2 · Digestive system
Cross-referenced to the 2028–2029 0653 section using original teaching from the related single-science courses. A 0653-specific objective-by-objective and Core/Supplement review is in progress. Written practice is self-checked and does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall large and small nutrient molecules, cell membranes and enzyme specificity.
- Use the stated diagram keys and evidence; models are not to scale.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which structure transports swallowed food to the stomach?
What you will learn
- Connect entry, transport, mixing and gastric digestion.
- Limit conclusions from a physical stomach model.
From mouth to stomach
Food enters through the mouth. Teeth physically break it up, and saliva moistens it and begins starch digestion. The oesophagus transports swallowed food to the stomach by coordinated muscular contractions.
The oesophagus is not the principal region of nutrient absorption. Its movement function is different from teeth breaking pieces and enzymes chemically changing nutrient molecules.
Combine stomach roles
The stomach temporarily holds and mixes food. Muscular contractions churn the contents with gastric juice, which includes acid and a protease. Physical mixing and chemical digestion occur together but are different mechanisms.
Material leaves the stomach into the duodenum. The stomach does not complete all digestion or absorb most nutrients; the small intestine continues the pathway.
Sources for this lesson
Pause and explain
Which stomach action is physical?
Worked example
A stomach diagram shows muscular squeezing and enzyme action. Give one physical and one chemical function.
Show the worked solution
- Squeezing churns/mixes.
- Protease contributes to protein breakdown.
- Do not treat muscle force as an enzyme.
Answer Muscles churn and mix food; gastric protease chemically digests protein.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
State one digestive function each for teeth, saliva and stomach muscles.
Give me a hint
Separate breaking, enzyme action and mixing.
Compare my reasoning
- Teeth break pieces.
- Saliva starts starch digestion.
- Stomach muscles churn/mix.
Teeth physically break food; saliva begins starch digestion; stomach muscles churn and mix contents.
Look for these in your work
- Three specific functions.
- Mechanisms distinct.
Why is oesophagus → stomach a transport route rather than evidence that the oesophagus absorbs most glucose?
Give me a hint
Movement along and across a wall differ.
Compare my reasoning
- Food moves along the canal.
- Absorption crosses the gut lining.
- Most nutrient absorption occurs in the small intestine.
The route shows transport along the canal, not the main absorption site.
Look for these in your work
- Along/across distinction.
- Correct main site.
A model stomach is squeezed while no enzyme is added. What can it represent, and what does it not demonstrate?
Give me a hint
Limit a physical model.
Compare my reasoning
- Squeezing models churning/mixing.
- It does not show protein molecule breakdown by protease.
It models physical mixing; it does not by itself demonstrate chemical digestion.
Look for these in your work
- Valid physical role.
- Chemical-evidence limit.
Common mistakes
- Transport is not automatically nutrient absorption.
- The stomach does not finish all digestion.
What can you explain now?
Which stomach action is physical?
Compare with the explanation
Muscular churning and mixing.
It changes food pieces and mixes contents.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain why muscle movement and enzyme action must be described separately.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.