Changes in the position and angulation of incisura during contractions of the isolated cat stomach.

Contractions change the configuration of the lesser curvature of the stomach while they indent the greater curvature. We studied these lesser curvature changes by measuring the position and angle of the gastric incisura on still frames captured from videotapes of isolated cat stomachs suspended in physiologic solution. In response to filling with 100 mL Krebs' solution stomachs generated a tonic contraction of the fundus/body segment and gave rise to a peristaltic contraction that spread from the body and through the antrum to the pylorus. In preparations where we left the duodenal cannula open we found that the incisura moves toward the gastro-oesophageal (GO) junction and the angle of the incisura widens as the contraction passes through the stomach and empties its contents. Furthermore, the angle of the incisura is most acute when the full stomach starts contracting in its fundic segment and again when the contraction involves the gastric sinus (the wedge-shaped segment adjacent to the incisura which forms the transition between the body and the antrum of the stomach). In preparations where the duodenal cannula was kept closed, the angle of the incisura becomes most acute when the contraction involves the gastric body and when the luminal pressure peaks. We conclude that changes in the position and angulation of the incisura are part of the mechanical response of the stomach to filling and emptying; unlike the peristaltic contraction along the greater curvature the net movement of the incisura goes in the orad direction. Movements of the incisura profoundly affect the configuration of the stomach and hence the distribution of luminal contents between various gastric segments. The gastric sling muscles are responsible for the formation of the gastric incisura but their role in any movements of the incisura remains to be defined.