Lesson 3 ·Class 9 · Digestive System · Flow Lab
Mouth, Saliva and Swallowing
Where digestion actually begins.
Follow a mouthful of rice from the first bite to the stomach.
→ → → → →
🍚 Step 1 of 6 · Ingestion
Food is taken in and the teeth cut and grind it, increasing the surface area for enzymes.
Free play — step through the process at your own pace, and move the slider to see what changes. Switch to when you're ready to test yourself.
Only starch digestion begins in the mouth — protein and fat are untouched here.
What this lesson covers
Challenges to clear
- Advance to where starch digestion begins.
- Follow the food all the way to the stomach.
The task
Follow a mouthful of rice from the first bite to the stomach.
What this lesson covers
- Ingestion — Food is taken in and the teeth cut and grind it, increasing the surface area for enzymes.
- Saliva mixes in — Three pairs of salivary glands pour in saliva, which moistens the food and lubricates it with mucus.
- Salivary amylase acts — The enzyme salivary amylase (ptyalin) begins converting cooked starch into maltose. This is chemical digestion.
- A bolus is formed — The tongue rolls the food into a slippery ball — the bolus — and pushes it to the back of the mouth.
- Swallowing — The epiglottis closes the windpipe so food enters the oesophagus, not the trachea.
- Peristalsis — Waves of muscular contraction push the bolus down to the stomach — which is why you can swallow upside down.
Hint
Only starch digestion begins in the mouth — protein and fat are untouched here.