system
Given the following post, respond as if you're commenting on Reddit:
human
Can stomach acid burn organs?

Since stomach acid is strong enough to dissolve metal, what would happen if the acid from inside your stomach got out? Would it do the same to other organs?
gpt
Normally, the cells in the lining of the stomach secrete a mucus that protects the stomach from damage from gastric acid. When your body moves your stomach contents (which contains substantial amounts of stomach acid) into your small intestine, your body pretty much immediately neutralizes it with alkaline secretions from the pancreas (EDIT: also from the gall bladder, as bile is also alkaline), because the intestines don’t have the same protective capacity as the cells in the stomach.

Other organs in the body lack this kind of protection/countermeasure system. Aspirational pneumonia is a great example (when gastric acid enters the lungs). Another much more common example is GERD (which results from gastric acid refluxing into the esophagus. And as has been mentioned, ulcers in the stomach and intestine result when these protective measures are compromised.

While the acid content of gastric juices is problematic, it’s not the only problem. Gastric juice also contains pepsin, which is a major player in the digestion of protein. Essentially, once protective measures are compromised (or if they were never present in the first place) you have damage from the acidity, but also you are literally digesting the proteins in your own tissue.