And to prevent our epithelial lining from destroying itself as a result of that high acidity, these mucol cells secrete this mucus that protects our epithelial lining from degradation. Now, as we see from this diagram, the mucous cells are found on the lining of that stomach and also on the upper portion of our exocrine gland ducts. So let's move on to our achieve cell. So, chief cells are also pretty easy to remember and that's because chief cells secrete a principal zymogen of the stomach known as Pipsinogen. So these cells, the chief cells release the principal or chief zymogen of the stomach, known as Pipsinogen. And once pepsinogen is actually released into our dust and it enters our aluminum of the stomach, if the PH is low enough, if the PH is around two, so if we have a very highly acidic environment, then our Pipsnogen will transform into the active form, the active enzyme known as pepsin.