Which of the following cells are NOT located in the stomach wall?

The correct answer is that beta cells are not located in the stomach wall. Beta cells are specialized cells found in the pancreas, specifically within the islets of Langerhans. They are primarily responsible for producing insulin, which regulates blood sugar levels, and are not involved in the digestive processes that take place in the stomach.

In contrast, parietal cells, chief cells, and mucous cells are all found within the gastric gland of the stomach wall. Parietal cells produce hydrochloric acid and intrinsic factor, which are essential for digestion and vitamin B12 absorption. Chief cells secrete pepsinogen, an inactive enzyme that is converted to pepsin in the presence of acid, facilitating protein digestion. Mucous cells produce mucus, which protects the stomach lining from the corrosive effects of gastric acid and helps lubricate food for easier passage through the digestive system.