Chapter 7 (page 27)

The Pyloric Sphincteric Cylinder in Health and Disease

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Chapter 7 (page 27)

Lymphatic Drainage

In a meticulous study of 30 post-mortem specimens, Jamieson and Dobson (l907) found that the lymph vessels in the walls of the stomach arise in the subepithelial interglandular tissue of the mucosa, from where they pass outwards between the glands to communicate with each other in the peri-glandular plexus. Vessels proceed from here into the subglandular plexus between the glands and muscularis mucosae. Short vessels then pierce the muscularis mucosae to break up on its outer surface to form the submucous plexus. Large vessels draining this plexus pass outwards through the muscular coats, communicating with the networks among the muscle fibres, and open into the subserous plexus. From the latter valved collecting vessels radiate to the curvatures of the stomach to enter the omenta. By means of injection techniques it was shown that fluid passed from the submucous to the subserous plexus, but not in the reverse direction.

Doubt had been expressed by previous authors as to the continuity of the gastric and duodenal plexuses. Jamieson and Dobson (l907) found that injection of the gastric submucous plexus showed free communication with the submucous plexus of the duodenum. Injection of the gastric subserous plexus showed a sharp demarcation at the pyloric ring, with the fluid flowing in the direction of the gastric curvatures. In only one specimen could direct communication between the gastric and duodenal subserous plexuses be demonstrated. However, many of the collecting vessels from the pyloric subserous network ran downwards over the duodenum to reach the subpyloric glands, and as they received vessels from the duodenum it was surmized that an indirect communication was formed in this way.

Horton (l928) on the other hand, demonstrated by means of injections of India ink that an almost complete block existed between the submucous lymphatics of the stomach and those of the duodenum at the pylorus. In contrast, the subserous lymphatics of the pyloric region were continuous with those of the duodenum.

Coller et al. (l94l) divided the lymphatics of the stomach into intramural, intermediary and extramural systems. The intramural system consists of 3 networks, viz. submucosal, intermuscular and subserosal. The submucosal lymphatic channels communicate freely throughout the submucosa of the stomach and to a lesser degree with the submucosal lymphatics of the duodenum; they also communicate freely with the intermuscular and subserosal networks. The intermediary system consists of numerous small channels between the subserosal network and the extramural collecting systems. The extramural system consists of four major zones of lymphatic drainage, corresponding to the arterial supply of the stomach. Ultimately all zones drain into the coeliac nodes around the coeliac arterial trunk on the anterior aspect of the aorta.

According to Eker (l951) the stomach should be considered to have the following 4 zones of lymphatic drainage:

The first zone comprises the upper two-thirds of the lesser curvature and a large part of the body of the stomach. The lymphatic drainage is into the left gastric nodes lying along the left gastric artery. These nodes are joined by lymphatics coming down from the lower part of the oesophagus, and their efferents proceed to the coeliac nodes.
The second zone of lymphatic drainage is from the distal part of the lesser curvature, including the lesser curvature of the pyloric region, to the suprapyloric nodes along the right gastric artery. Eker (l951) stressed the fact that this zone consists of "only a small area in the lower part of the pyloric region". Efferent channels from the suprapyloric nodes drain to the hepatic and ultimately to the coeliac and aortic nodes.
Most of the pyloric part of the stomach as well as the right (i.e. lower) half of the greater curvature constitute the third zone. The extramural lymphatics from these areas drain into the right gastro-epiploic nodes in the gastrocolic ligament, lying along the right gastro-epiploic vessels, and into the pyloric nodes on the anterior surface of the head of the pancreas. The direction of lymph flow is from above downwards, towards the pylorus and the nodes between the head of the pancreas and second part of the duodenum. From these groups, collectively called the subpyloric glands (which also drain the first part of the duodenum), efferent vessels pass along the gastro-duodenal artery to the hepatic nodes along the hepatic artery, and thence to the coeliac nodes.
The fourth zone is from the left (i.e. upper) half of the greater curvature and the gastric fornix. From here lymph vessels pass to the left gastro-epiploic nodes, lying along the left gastro-epiploic artery, proceed to the pancreatico-lienal nodes along the splenic artery, and ultimately to the coeliac nodes.

Lehnert et al. (l985) studied the distribution of lymph and blood capillaries by light and transmission electron microscopy in 16 endoscopic biopsy and surgical resection specimens of human gastric mucosa and submucosa. Four were normal and 12 showed evidence of gastritis. A clear distinction between small mucosal blood and lymph capillaries was not always possible with light microscopy; a distinction could be made by electron microscopy. This showed blood capillaries at all levels of the lamina propria, and especially at its upper levels, as well as in the submucosa. Lymph capillaries on the other hand, could not be demonstrated in the upper and middle regions of the lamina propria; lymphatics were only present in the deep lamina propria adjacent to the muscularis mucosae. Larger lymph vessels were observed in the submucosa. It was concluded that the entire human gastric mucosa had a rich supply of blood capillaries, many of which were adjacent to the gastric glands and surface epithelium, but that lymphatic capillaries were present only in the deep lamina propria. It seemed if earlier descriptions, derived from light microscopy, needed revision.