Cells in the wall of stomach produce pepsinogen. which plays a role protein digestion. Why these cells digest themselves?

Cells in the wall of the stomach do not digest themselves. They produce pepsinogen, which is a zymogen or inactive form of the enzyme pepsin. Pepsinogen is secreted into the stomach lumen, where it is activated by the acidic environment and converted into pepsin. Pepsin then begins to break down proteins in the food we eat.

The cells in the stomach wall are protected from being digested by pepsin by a thick layer of mucus. This mucus layer also helps to prevent the stomach acid from damaging the cells.

So, while cells in the stomach wall do produce pepsinogen, they do not digest themselves thanks to the protective mucus layer.