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WonderBody fact

The stomach produces hydrochloric acid, giving its contents a pH of roughly 1.5 to 3.5, on a scale where 7 is neutral and lower numbers are more acidic. That is acidic enough to help break down food and kill many of the microbes swallowed with it.

Human biology

Health

The story behind the card

The acid is made by parietal cells in the stomach lining, and an adult stomach releases about 1.5 litres of gastric juice a day. The acid unfolds proteins and turns an inactive substance, pepsinogen, into pepsin, the enzyme that starts protein digestion. Other cells coat the lining with thick mucus and bicarbonate, a natural antacid, so the acid does not reach the wall; drugs such as aspirin can weaken this barrier. Early understanding of gastric juice owed much to an accident. In 1822 a young fur trader, Alexis St. Martin, was accidentally shot on Mackinac Island in Michigan, and his wound healed leaving an opening into his stomach. The army surgeon William Beaumont studied digestion through it for years, and his 1833 book showed that gastric juice breaks food down chemically.

Türkçe oku
Mide, hidroklorik asit üretir ve bu asit mide içeriğinin pH değerini genellikle 1,5 ile 3,5 arasına indirir. pH ölçeğinde 7 nötr kabul edilir; sayı küçüldükçe asitlik artar. Bu asitlik, besinlerin parçalanmasına yardım etmeye ve onlarla birlikte yutulan birçok mikrobu öldürmeye yeter.

Asidi mide duvarındaki parietal hücreler üretir; yetişkin bir insanın midesi günde yaklaşık 1,5 litre mide suyu salgılar. Asit, proteinlerin yapısını çözer ve pepsinojen adlı etkisiz bir maddeyi, protein sindirimini başlatan pepsin enzimine dönüştürür. Başka hücreler mide duvarını kalın bir mukus tabakasıyla ve doğal bir asit giderici olan bikarbonatla kaplar; böylece asit duvara ulaşamaz. Aspirin gibi ilaçlar bu korumayı zayıflatabilir. Mide suyunun nasıl çalıştığını anlamamızda bir kazanın büyük payı var. 1822'de ABD'nin Michigan eyaletindeki Mackinac Adası'nda genç bir kürk tüccarı olan Alexis St. Martin kazara vuruldu; yarası iyileşti ama midesinde dışarı açılan bir delik kaldı. Ordu cerrahı William Beaumont yıllarca bu açıklıktan sindirimi inceledi ve 1833'te yayımladığı kitapta mide suyunun besinleri kimyasal yolla parçaladığını gösterdi.

Sources and further reading

Background reading: Stomach
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