Stomach

Acid & churn

How does the stomach work?

A muscular bag that churns food with acid and enzymes into a thick liquid called chyme.

Acid

Hydrochloric acid (pH around 1.5–3.5) unfolds proteins and kills many microbes.

Protection

A thick mucus layer protects the stomach wall from its own acid.

Vitamin B12 link

Stomach cells make intrinsic factor, which the body needs to absorb vitamin B12 later in the intestine.

Evidence & sources

• Stomach muscles mix food with digestive juices before emptying it into the small intestine. Evidence: established. Known: Basic physiology. Unknown: — Source: NIH NIDDK, Your Digestive System & How It Works (Current revision).

Connected topics

• Protein
• Vitamin B12
• Iron
• Small Intestine

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General education only, not medical advice. Drafted Oct 2026 · pending qualified expert review.