What begins the oral transit phase of swallowing?

The oral transit phase of swallowing is initiated by the voluntary posterior propulsion of the bolus by the tongue. During this phase, after the food has been prepared in the oral cavity, the tongue plays a crucial role in pushing the bolus toward the back of the mouth, facilitating the transition from oral to pharyngeal swallowing. This action requires precise coordination of the tongue's movements and is a key part of the swallowing process.

Moving the bolus into the stomach, relaxing the lower esophageal sphincter, or chewing food into smaller pieces are subsequent processes that occur later in the swallowing mechanism and are not involved in the initial phase of oral transit. Chewing, for instance, pertains more to the preparation of food for swallowing rather than the act of transporting the bolus itself. Thus, the initiation of the oral transit phase is centered around the tongue's role in moving the bolus posteriorly, leading into the pharyngeal phase of swallowing.