The goblet, or mucus cell, is the only unicellular exocrine gland in the human body. It is found in the lining of the intestines and other parts of the digestive system, the respiratory tracts, and the conjunctiva of the eye. Goblet cells produce a carbohydrate-rich glycoprotein called mucin, which is then secreted in the form of mucus, a thick, lubricating fluid.