Figure 5. Short length (SL) contractions propagate both anally and orally in duodenum and jejunum.

The upper panel of A shows anally propagating SL contractions (black arrows) induced by decanoic acid (1 mm) in a segment of jejunum. The middle panel shows an expanded image of the region within the box in the upper panel. The bottom panel tracks the diameter at a single point shown by the dashed line. In this case, the constriction begins in the middle of the segment, is clearly preceded by a dilatation and propagates anally, although it does not reach the anal end. In B, orally propagating SL contractions (box) and stationary contractions (small arrows) can be seen in the jejunum and in this case the SL contractions are not accompanied by a dilatation. The horizontal dashed line in the middle panel provides a reference to allow the propagation of the constriction to more oral points to be clearly seen. In C, a band of orally propagating SL contractions in the duodenum can be seen (small arrows) and these are preceded by dilatations.