Lesson 4 ·Class 9 · Digestive System · Flow Lab
The Stomach
Gastric juice and protein digestion.
The stomach is a churn, an acid bath and a protein factory at once.
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🌀 Step 1 of 6 · Food arrives
The bolus enters through the cardiac sphincter and the stomach begins to churn it.
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.
Pepsin only works in acid — which is exactly why the stomach makes HCl.
What this lesson covers
Challenges to clear
- Advance to the enzyme that digests protein here.
- Step through the whole stomach stage.
The task
The stomach is a churn, an acid bath and a protein factory at once.
What this lesson covers
- Food arrives — The bolus enters through the cardiac sphincter and the stomach begins to churn it.
- Hydrochloric acid — Gastric glands secrete HCl. It kills most swallowed bacteria and makes the medium acidic for gastric enzymes.
- Pepsin activated — Inactive pepsinogen is converted by HCl into active pepsin, which breaks proteins into peptones.
- Mucus protects — A mucus layer stops the stomach digesting its own wall. Where it fails, an ulcer forms.
- Chyme forms — After a few hours the food is a semi-liquid acidic paste called chyme.
- Into the duodenum — The pyloric sphincter releases the chyme into the duodenum a little at a time.
Hint
Pepsin only works in acid — which is exactly why the stomach makes HCl.