THE MECHANICS OF GASTRIC EVACUATION

Abstract

Simultaneous optical registration of intralumen pressures of the pyloric antrum and duodenal bulb of un-anesthetized dogs combined with fluoroscopic observations of this region was employed in studying gastric evacuation. In each evacuation cycle the 1st period of evacuation (period A) was associated with a moderate basal pressure gradient from antrum to bulb. During this interval the pyloric sphincter and duodenal bulb offered very little resistance to expulsion. Since the antral pressure remained low, the energy of the antral contraction occurring at that time probably was chiefly transformed into propulsive force. 898 As the accumulation of material in the duodenum and the contraction of the sphincter increased the resistance distally, the advancing antral peristaltic wave elevated the antral pressure and the antral phasic pressure wave was produced. Gastric evacuation persisted (period B) under the aug- mented pressure head until terminated by several factors, among which was the completely contracted sphincter. Bulbar contraction occurred at this time and caused bulbar emptying, but regurgitation was prevented by the contracted sphincter.