belching

physiology

Also known as: eructation

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Last updated

July 23, 2026

Quick Summary

Belching, also known as eructation, is the expulsion of gas from the stomach through the mouth. This gas is primarily swallowed air, with some by-products of digestion.12

Normally, the digestive tract contains 150 to 500 cubic cm of gas. When eating, air enters the stomach and is either belched out or passed to the intestines. Stomach gas is composed of oxygen, carbon dioxide, and nitrogen. Some oxygen is absorbed by the blood, while carbon dioxide is formed by food reduction. Nitrogen is typically passed on.2

The small intestine absorbs some gases and moves the rest to the large intestine. In the large intestine, bacterial fermentation produces additional gases like hydrogen, methane, and hydrogen sulfide. Excess gas in the colon is expelled as flatulence. Belching can also be a symptom of indigestion, which can be caused by stress, improper eating habits, or hypersensitivity to certain foods.23

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human digestive system
Intestinal gas
…is either regurgitated (as in belching) or absorbed in the stomach. Anxiety or eating quickly induces frequent swallowing of air with consequent belching or increased rectal flatus. Although some of the carbon dioxide in the small intestine is due to the interaction of hydrogen ions of gastric acid with bicarbonate,…
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…is either regurgitated (as in belching) or absorbed in the stomach. Anxiety or eating quickly induces frequent swallowing of air with consequent belching or increased rectal flatus. Although some of the carbon dioxide in the small intestine is due to the interaction of hydrogen ions of gastric acid with bicarbonate,…
Read More

speech
Esophageal voice
…esophagus and then eructated (belched), as many people can do without practice. The sound generator is formed by the upper esophageal sphincter (the cricopharyngeus muscle in humans). As a replacement for vocal cord function, the substitute esophageal voice is very low in pitch, usually about 60 cycles per second…
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…esophagus and then eructated (belched), as many people can do without practice. The sound generator is formed by the upper esophageal sphincter (the cricopharyngeus muscle in humans). As a replacement for vocal cord function, the substitute esophageal voice is very low in pitch, usually about 60 cycles per second…
Read More