Pharyngeal pump and esophageal transit.

In deglutition the pharynx appears to act as a pump to "inject" boluses into the esophagus. A new method for measuring the velocity profile of the leading edge of a radionuclide bolus has been developed and applied to boluses of different viscosity--water and treacle--in nine normal volunteers. The results show that the more viscous bolus (treacle) acquires a slower initial "injection" velocity (152 mm/sec vs 236 mm/sec) that only propels it over the proximal half of the esophagus. Peristaltic action must drive the bolus over the distal half. With water boluses, however, the higher initial velocity is sufficient to propel a part of the bolus at least to the gastroesophageal junction leaving minimal "work" to be performed by esophageal peristalsis. This confirms the important role of the pharyngeal pump in deglutition. The pump may be the major mechanism for ingestion of nonviscous liquids (water), peristalsis merely being required to "sweep up" what remains in the esophagus.