When the mucus layer of the stomach or duodenum becomes too thin, acid can erode the cells lining these tissues. This results in a lesion known as a peptic ulcer, as shown below.
10% of Americans will develop an ulcer in their lifetime. Despite common beliefs, these ulcers are not caused by stress or spicy foods. Most ulcers are believed to be caused by the acid-resistant bacteria, Helicobacter pylori. 30-40% of Americans are infected with this bacteria. Helicobacter pylori causes a thinning of the mucus that protects the stomach and duodenum from gastric acid. It is not clear how Helicobacter pylori is transmitted, though it may be through contaminated food or water. It might also be spread through contact with vomit, feces, or saliva of an infected person1.
Prolonged use of nonsteroidal anti-inflammatory drugs (NSAIDS) such as aspirin, ibuprofen, or naproxen (Aleve) are also frequent causes of peptic ulcers. NSAIDs inhibit the production of a protective eicosanoid1. The first video describes and illustrates this effect. It describes how goblet cells secrete mucus in the stomach. This is not correct, they secrete mucus in the intestine. It should be neck cells in the stomach.
The second video shows what two gastric (stomach) ulcers look like.