Squamous epithelial cells divide about once in every 24-hour period and line the human mouth as part of the buccal muscosa. The cells secrete mucin, the substance that is the principal component of mucus. With the additional help of the salivary glands, the mucin keeps the mouth's interior moist. The mouth needs to maintain moisture in order to help secreted enzymes soften food, facilitate swallowing and begin the digestion process.