So, mucus cells are easy to remember because what their function is to secrete a special type of substance known as mucus. Now, mucus is a fluidlike substance that consists of glycoprotein, water, electrolytes, so our ions as well as other molecules. And what the mucous does is it ultimately lubricates our stomach lining. And that allows the movement of our fluid along of our food, along that stomach lining. And what it also does, and perhaps the more important function of the mucus, is to basically provide protection to the epithelial cells, the epithelial lining of our stomach. So, as we'll see in just a moment, the stomach has a very high acidity, a very low PH, and that can easily destroy the lining of that stomach.