Mouth

Digestion of food begins in the oral cavity.

Food is masticated by teeth and moistened by saliva secreted from the salivary glands.

Enzymes in the saliva begin to digest starches and fats.

With the help of the tongue, the resulting bolus is moved into the esophagus by swallowing.

There are three major glands that secrete saliva: the parotid, the submandibular, and the sublingual.

Saliva contains mucus that moistens food and buffers the pH of the food.

Saliva also contains immunoglobulins and lysozymes, which have antibacterial action to reduce tooth decay by inhibiting growth of some bacteria.

Saliva contains an enzyme called salivary amylase that begins the process of converting starches in the food into a disaccharide called maltose.

Another enzyme, lipase, is produced by the cells in the tongue.

It is a member of a class of enzymes that can break down triglycerides.

Lingual lipase begins the breakdown of fat components in the food.

The chewing and wetting action provided by the teeth and saliva shape the food into a mass called the bolus for swallowing.

The tongue aids 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 tracheal opening, the glottis, is covered by a cartilaginous flap, the epiglottis.

When swallowing, the epiglottis closes the glottis, allowing food to pass into the esophagus, not into the trachea, preventing food from reaching the lungs.