BBC Science & Nature
stomach oesophagus sphincter hydrochloric acid peristalsis digestion digestive system
Your stomach is a short-term food storage facility. Find out how it breaks food down and mixes it with juices secreted by your stomach lining.
Food store

Your stomach is a short-term food-storage facility. This allows you to consume a large meal quickly and then digest it over an extended period of time. When full, your stomach can hold around one litre of chewed up food.

Swallowed food is propelled down your oesophagus into your stomach. Food is enclosed in your stomach by two circular muscles, known as sphincters.

Chemical breakdown

As soon as food enters your stomach, your stomach lining releases enzymes that start breaking down proteins in the food. Your stomach lining also secretes hydrochloric acid, which creates the ideal conditions for the protein-digesting enzymes to work. The potent hydrochloric acid kills bacteria, protecting your body from harmful microbes which can enter your body in food.

Your stomach protects itself from being digested by its own enzymes, or burnt by the corrosive hydrochloric acid, by secreting sticky, neutralising mucus that clings to the stomach walls. If this layer becomes damaged in any way it can result in painful and unpleasant stomach ulcers.

Physical breakdown

Waves of muscular contraction along your stomach wall, known as peristalsis, break food down into smaller pieces, mix it with fluids secreted from your stomach lining and move it through your stomach. This creates a mixture that resembles thick cream.

Release of food into small intestine

When food has been broken down sufficiently, small amounts are squirted out of your stomach into your small intestine for further processing. This normally occurs within four hours of eating a meal, but can take six or more hours if your meal has a high fat content.

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