Mouth

The mouth is the point of entry of food into the digestive system. The food consumed is broken into smaller particles by the chewing action of the teeth. The extensive chemical process of digestion begins in the mouth. As food is being chewed, saliva, produced by the salivary glands, mixes with the food. Another enzyme called lipase is produced by the cells in the tongue. The lingual lipase begins the breakdown of fat components in the food. The chewing and wetting action provided by the teeth and saliva prepare the food into a mass called the bolus for swallowing. The tongue helps in swallowing by moving the bolus from the mouth into the pharynx. The pharynx opens to two passageways: the trachea, which leads to the lungs, and the esophagus, which leads to the stomach. The trachea has an opening called the glottis, which is covered by a cartilaginous flap called the epiglottis. When swallowing, the epiglottis closes the glottis and food passes into the esophagus and not the trachea. This arrangement allows food to be kept out of the trachea.

Figure 1: Parts of the mouth: (1) nasal cavity, (2) lips, (3) jaw, (4) tongue, (5) larynx, (6) oral cavity, (7) uvula, (8) pharynx, (9) esophagus, (10) teeth, (11) sublingual gland, (12) submandibular gland, (13) parotid gland.