Relationship of the Structure of Ureteral Muscularis to in vitro Spontaneous Contractions

Abstract

We investigated the anatomical structure of the smooth muscle layers of the mid portion of the canine ureter. In transverse sections the inner muscle bundles appear to be oriented longitudinally and the outer muscle bundles appear to be oriented in a circular configuration. In sections cut parallel with the longitudinal axis of the ureter, the inner and outer bundles appear to be oblique and are oriented in a mesh-line manner. In oblique sections, cut parallel with the helically oriented ureteral muscle, bundles appear to be oriented in a lengthwise configuration. These anatomical studies show that canine ureteral smooth muscle is composed of spiral fibers in a mesh structure and that helical muscle strips which include a significant percentage of continuous bundles have a greater capacity to generate spontaneous contractions in vitro than do transverse and longitudinal muscle strips.

Evaluation of ureteric contraction: a comparison among ring, spiral‐cut and longitudinal segments

“…As EFS induces contraction through the release of various mediators from the tissue and carbachol stimulates contraction via muscarinic receptors, all four suspension methods are suitable for analysing ureteric responses to a variety of stimuli. These results are in contrast to a previous report by Morita et al [13] who, using canine ureter, showed that spiral segments were more responsive to noradrenaline than were longitudinal or ring segments. In addition, that report indicated that ring and longitudinal segments had very low levels of spontaneous contraction, caused by disruption of the muscular bundles, which is avoided using the spiral‐cut method.…”

“…The reports mentioned used human or sheep ureters to obtain spontaneous contractility. The present results indicate that swine ureters also show spontaneous contractility, in contrast to the work of Morita et al [13] with canine ureter. This may suggest that the swine ureter provides a better model for the study of ureteric physiology than the canine ureter.…”

“…Similarly, it has been reported that muscular bundles occur in two layers, an outer layer of circular bundles and an inner layer of longitudinal bundles [12]. Morita et al [13] investigated the anatomical structure of the smooth muscle layers of the midportion of the canine ureter. By studying transverse sections, they re‐affirmed that the outer muscular bundles are orientated in a circular fashion while the inner bundles are orientated longitudinally.…”

“…By studying transverse sections, they re‐affirmed that the outer muscular bundles are orientated in a circular fashion while the inner bundles are orientated longitudinally. Based on these findings, they have used a spiral‐cut segment of ureter in their tissue‐bath assays, suggesting that this segment preserves more continuous muscular bundles and therefore can generate increased spontaneous contraction [13,14]. Unfortunately, the availability of long, viable human ureteric segments for use in research is limited and often precludes the use of spiral‐cut segments.…”

Electrical propagation in the renal pelvis, ureter and bladder

“…, Morita et al . ). Therefore, and as expected, the nature of muscle contractions and electrical activities are not the same among these structures.…”