Simple columnar epithelium forms a lining of the stomach, small intestine, colon, gall bladder, gastric glands, intestinal gland, and pancreatic lobules. Since here it performs the secretory functions, it is called the glandular epithelium. Certain cells of the columnar epithelium of the stomach and intestine produce mucus which forms a fine mucus coating over the epithelium. These mucus-producing cells are called goblet cells. The epithelium having mucus-secreting cells along with underlying connective tissue is called mucous membrane or mucosa.