What are the four stages of mastication and deglutition?

The four stages of mastication and deglutition are:

The oral preparatory stage (mastication) occurs when food is prepared for

swallowing. During this stage, the lips seal, thereby keeping the food in the individual's mouth. The lingual muscles and muscles of mastication grind up the food. Finally, the food mixes with saliva to form a bolus (ball of fluid or food) that can be swallowed.

The oral stage occurs when an individual actually swallows the bolus. The tongue pushes the bolus back toward the oropharynx. The mandibular and tongue muscles are involved in the oral stage. The oral transit time is the time needed to move the bolus to the point of initiation of the pharyngeal stage of swallowing.

The pharyngeal stage is a complex sequence of reflexively controlled events. This stage begins when the bolus comes in contact with the faucial pillars, after which it is propelled through the pharynx. The esophageal sphincter relaxes, which enables it to receive the bolus. Also, a tight seal forms, which protects the airway. Food passes over the epiglottis to the esophagus.

The esophageal stage is the last stage of mastication and deglutition. Swallowing involves peristaltic movement of the bolus through the esophagus and then into the stomach.