mouth

the opening that forms the beginning of the ALIMENTARY CANAL and through which food enters the digestive process. The entrance is guarded by the lips, behind which lie the upper and lower sets of teeth (see TOOTH ) embedded in the JAW . The roof of the mouth is called the PALATE , the front part being hard and immobile while behind lies the mobile soft palate. The TONGUE is situated behind the lower teeth, and SALIVARY GLANDS which are present secrete saliva into the mouth through small ducts. Saliva contains the ENZYME ptyalin, which begins the breakdown of starch while the chewing action of the teeth and manipulation with the tongue reduce the food to a more manageable size so that it can be swallowed.