Mucosa-submucosa Layer Research Articles

The origins of innervation of the esophagus of the dog

This study defined the origins of extrinsic efferent and afferent innervation of the normal canine esophagus. When all the layers of the wall of the 3 esophageal regions (cervical, thoracic and abdominal) were injected with horseradish peroxidase (HRP), labeled nerve cells were found in the nucleus ambiguus (NA) and parasympathetic nucleus of X (PX) of the brainstem. Most labeled cells in the NA were located in the compact column (retrofacial nucleus) while labeled cells in the PX were located in separate rostral and caudal areas. There was no somatotopic organization in either the NA or PX. Labeled sympathetic postganglionic neurons were found in the cranial cervical, middle cervical, cervicothoracic, thoracic sympathetic trunk and celiacomesenteric ganglia. The HRP injection of the esophageal wall labeled sensory cell bodies in the glossopharyngeal, proximal and distal vagal, and C2-T6 spinal ganglia. There was no discernible pattern of distribution of labeled cells in the autonomic or sensory ganglia. When the HRP injections were confined to the mucosa-submucosa layers of the thoracic esophagus, a small number of labeled cells were identified in the NA; however, no labeled cells were found in the NA when injections were confined to the mucosa-submucosa of either the cervical or abdominal esophageal regions. With these confined injections, the labeled nerve cells appeared in the rostral part of the PX. Thus, it appeared that the internal tunics of the esophagus (i.e., the mucosa and submucosa) were innervated by neurons in the rostral PX while the muscular tunic was innervated by neurons in the caudal PX and the rostral NA. After mucosa-submucosa injections, labeled sympathetic neurons appeared in the same ganglia that were identified after whole wall injections and these had a similar random distribution. These injections also labeled neurons in the glossopharyngeal, proximal vagal, and distal vagal ganglia, but unlike the whole wall injections there was no labeling in the spinal ganglia. This suggested that the labeled cells of the spinal ganglia seen after whole wall injections conveyed impulses from the tunica muscularis and serosa.

Effect of polycythemia on gastrointestinal blood flow and oxygenation in piglets.

Gastrointestinal blood flow and oxygenation were measured before and after the induction of polycythemia in newborn piglets. Sixty minutes after exchange transfusion with age-matched packed red blood cells, hematocrit and in vitro whole blood viscosity increased, while 51Cr-measured blood volume did not change. Cardiac output and total gastrointestinal blood flow (the sum of stomach, jejunum, ileum, and colon blood flows) decreased a similar degree after exchange transfusion, although the reduction in total gastrointestinal blood flow was not uniform in all regions of the gastrointestinal tract. Specifically, blood flow to the stomach and mucosa-submucosa layer of the small bowel decreased, whereas that to the colon and muscularis-serosa layer of the small bowel remained unchanged. Gastrointestinal O2 delivery increased after exchange transfusion because of the increase in arterial O2 content consequent to polycythemia. The arteriovenous O2 content difference remained unchanged following exchange transfusion, and gastrointestinal O2 consumption thus decreased 49 +/- 2%. After a test meal, postprandial values for gastrointestinal blood flow and oxygenation in polycythemic piglets increased to levels similar to postprandial values reported previously in normal newborn piglets.

Effect of graded arterial occlusion on ileal blood flow distribution.

SummaryThe reactive hyperemic response of the intestinal vasculature to graded arterial occlusion is often used to delineate mechanisms involved in the intrinsic regulation of intestinal blood flow. This study assesses if the reactive hyperemic response to 60- and 120-sec arterial occlusions occur uniformly throughout the wall of the small intestine. Radiolabeled microsphere injections were used to determine blood flow distribution in the mucosa-submucosa and muscu-laris layers of the small intestine under control conditions and during 60- and 120-sec arterial occlusion. The results of this study suggest that relatively uniform increases in intestinal wall blood flow occurs only for an occlusion period of 60 sec. Increasing the duration of the arterial occlusion to 120 sec results in a predominant hyperemia in the muscularis layer.

Intramural blood flows and flow distribution in the feline small intestine during arterial hypotension.

The vascular reactions of the parallel-coupled vascular sections of the small intestine were studied during hypotension at two different levels of intestinal arterial inflow pressure, using a 85Kr elimination technique. The regional hypotension was accomplished by partially occluding the superior mesenteric artery with a clamp and maintained for 2 h. At the higher level (50-55 mmHg) total intestinal blood flow decreased but not to the same relative extent as blood pressure due to the autoregulatory capacity of the intestinal vascular bed. The flow autoregulation was also reflected in a decreased blood flow resistance. The distribution of blood to the muscularis and mucosa-submucosa layer, respectively, did not change significantly during or after hypotension as compared to the prehypotensive level, since the relative flow decrease was the same in the mucosa-submucosa and in themuscularis. At the lower arterial pressure level (30-35 mmHg) a more marked decrease of intestinal blood flow and flow resistance was observed as compared to the experiments performed at the 50-55 mmHg pressure level. Moreover, muscularis blood flow was relatively more decreased than blood flow in the mucosa-submucosa implying the fraction of total blood flow diverted to the muscularis was significantly decreased. Despite this redistribution of blood flow, a histological damage was apparent only in the mucosa, particularly at the villous tips.