The Pyloric Sphincteric Cylinder in Health and Disease

Go to chapter: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39
Chapter 8 (page 31)

It then continues along the lesser curvature, giving off 4 to 6 posterior gastric branches. Latarjet (l921) called the most inferior and also the largest of these branches the principal posterior nerve of the lesser curvature; this has subsequently become known as the posterior nerve of Latarjet. Together with the other posterior branches it innervates the posterior wall of the stomach, with the exception of the pylorus and immediate prepyloric region. It also anastomoses with sympathetic twigs from the coeliac plexus, as well as with the principal anterior nerve of the lesser curvature.

McCrea's (l924) findings are similar to those of Latarjet, but he terms the branch from which the posterior gastric twigs arise, the "stem". Thus the stem gives off branches to the posterior aspect of the proximal portion of the body of the stomach. It then continues downwards, giving off branches to the posterior surface of the body and pyloric "antrum", the most distal being distributed in the region of the incisura angularis. According to McCrea the posterior vagus does not reach the pyloric canal.

Mitchell's (l940) findings are almost identical. What he calles the posterior gastric nerve (McCrea's "stem") gives off branches at intervals which pass to the stomach, but the terminal branches extend only to the pyloric "antrum", failing to reach the pyloric "sphincter". Slender hepatic twigs may also be given off towards the porta hepatis.

In 50 dissections of the posterior vagal trunk, Jackson (l948) charted the gastric branches and determined the point of origin of the coeliac branch. The principal posterior nerve of the lesser curvature (nerve of Latarjet) was identified in 19 instances. It proceeded along the lesser curvature in the direction of the pylorus, but, before reaching it, turned across the posterior surface of the stomach towards the greater curvature. Jackson concluded that the vagal supply to the pylorus was via the hepatic branches of the anterior vagus.

According to Skandalakis et al. (l986) the posterior gastric division forms the posterior nerve of Latarjet. The posterior gastric division usually terminates higher on the lesser curvature than the anterior gastric division; in a small minority of cases it reaches the pylorus. The most frequent pattern of the posterior gastric division is that described by McCrea (l924), which is a typical, but not universal, pattern.

Parasympathetic Ganglia

The left vagus supplies efferent preganglionic fibres mainly to the anterior surface, and the right vagus mainly to the posterior surface of the stomach. In addition both vagi send branches to the coeliac plexus. The parasympathetic preganglionic vagal fibres penetrate the layers of the gastric wall, to form synapses in the ganglion cells of the plexus of Auerbach between the longitudinal and circular muscle coats, and in the plexus of Meissner in the submucosa. From the ganglia postganglionic fibres emerge to supply the musculature and mucosa. According to Horton (l928), Auerbach's plexus is continuous from the pyloric region to the duodenum.

In addition to the myenteric (Auerbach's) and submucous (Meissner's) plexuses, Rash and Thomas (l962) described a third group, namely the subserous plexuses; they also mentioned the differentiation of enteric neurones into argyrophilic Dogiel Type I cells with short dendrites, and argyrophobic Dogiel Type II with fewer but longer dendrites. According to Smith (l970) the axons of argyrophilic neurones do not leave the plexuses and do not reach muscle fibres; their function is to coordinate peristalsis. The axons of argyrophobic cells, which are strongly cholinergic, form secondary and tertiary plexuses and supply muscle fibres; they act by initiating contractions. The general effect of myenteric plexus damage is loss of coordinated muscular contractions which serve to propel luminal contents caudally; this may lead to local muscular hypertrophy, e.g. hypertrophic pyloric stenosis (Chap 23).


The investigators quoted, namely Latarjet (l921), McCrea (l924), Mitchell (l940), Jackson (l948) and Skandalakis et al. (l986), found that the main, and in most cases the only, nerve supply from the anterior vagus to the pylorus is via its hepatic branch or branches. The region supplied in this way encompasses the distal "few centimetres" of the stomach, the pylorus and first part of the duodenum. While none of the authors referred to the findings of Cunningham (l906), Forssell (l913) or Torgersen (l942), it is clear that the region of the pylorus innervated in this way, corresponds to the pyloric sphincteric cylinder.

In the vast majority of cases the principal anterior nerve of the lesser curvature (nerve of Latarjet) does not innervate the sphincteric cylinder. A few exceptions were mentioned. Mitchell (l940) stated that in some cases a few fibres from the anterior vagus might reach the pylorus directly from gastric branches higher up. Skandalakis et al. (l986) found that Latarjet's nerve might occasionally proceed as far as the duodenum; in these cases there was still a separate branch from the hepatic division to the pylorus.

The investigators quoted found that the posterior vagus (including the posterior nerve of Latarjet) does not usually innervate the pylorus and prepyloric region, the most distal twigs extending only as far as the incisura angularis or the "commencement of the antrum". It is clear that the region which is not innervated by the posterior vagus, corresponds to the pyloric sphincteric cylinder. One of the few exceptions was mentioned by Skandalakis et al. (l986); in a small minority of cases they found that fibres of the posterior gastric division could reach the pylorus.

It is concluded that the vagal supply to the pyloric sphincteric cylinder (which includes the pyloric ring musculature) and to the first part of the duodenum, occurs via the hepatic branch of the anterior vagus in the vast majority of cases; the hepatic branch (or branches) breaks up into the superior and inferior pyloric nerves, supplying the cylinder.

Previous Page | Table of Contents | Next Page
© Copyright PLiG 1998