The Pyloric Sphincteric Cylinder in Health and Disease

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Chapter 5 (page 23)

Royston et al. (l978) found in patients with duodenal ulcer, that the mean area of the "antrum", as defined histologically, was double the mean antral area defined as the alkaline zone in the pH studies of Capper et al. (l962, l966).

The test of Moe et al (l965, l966) was based on the differential excretion of dyestuffs from the gastric corpus and the "antrum" in dogs. The mean area of the "antrum" was found to occupy 20 percent of the total gastric area, with a range of 10 to 30 percent. A modification of the test was used by Hedenstedt et al (l967) in humans, the results being controlled histologically. On the whole, the pyloric zone was found to be larger than that determined by Moe's test. In all cases the extent of pyloric mucosa was greater on the lesser than on the greater curvature. Amdrup et al (l972) used the congo red test for a precise determination of the "antrum" prior to antrectomy for gastric ulcers. In their experience the "antrum" in gastric ulcer cases was often larger than in duodenal ulcer cases, sometimes extending high up on the lesser curvature and occasionally as far as the cardia.


The duodenal mucous membrane also consists of 3 layers, but these differ from those of the stomach in several respects.

Muscularis Mucosae

The muscularis mucosae, consisting of outer longitudinal and inner circular fibres, forms the border between mucosa and submucosa. It is pierced by the ducts of Brunner's glands located in the submucosa; from it muscular strands extend into the cores of the villi on the luminal surface.

The villi are finger-like projections about 1.0mm in height, on the surface of the mucosa; they are covered by a layer of columnar cells which themselves have a brush border of microvilli.

Lamina Propria

The lamina propria, consisting of a network of reticular fibres and a loose network of connective tissue, forms the cores of the villi. It contains lymphocytes, plasma cells and occasional eosinophils. The core of each villus also contains a lymphatic vessel continuous with the lymphatic plexus of the submucosa, smooth muscle fibres continuous with the muscularis mucosae, a nerve twig from Meissner's plexus in the submucosa, an arteriole and a venule.

Between the villi are the crypts of Lieberkühn (also known as the intestinal glands); these are simple tubular glands lined by low columnar epithelium. The ducts of Brunner's glands open into the base of the crypts.

Epithelial Lining

The epithelial lining of the luminal surface of the duodenal mucosa consists of the columnar cells mentioned above, interspersed with goblet cells, Paneth cells and APUD cells (Chap. 9).

The columnar cells produce a variety of digestive enzymes and have an absorptive capacity; they are much more numerous in the remainder of the small bowel than in the duodenum. The goblet cells secrete mucus. Paneth cells are located in the base of the crypts of Lieberkühn. Each cell is pyramidal in shape with a broad base resting against the basal lamina, and a narrow apex facing the lumen; it shows features of exocrine secretion with prominent secretory granules said to contain high activities of lysozyme, a bacteriolytic enzyme that degrades bacterial cell walls (Erlandsen et al. l974). There is speculation that Paneth cells may help to regulate the microbiological flora; however, their role in the function of the small intestine is largely unknown (Trier and Madara l98l). They increase in number from duodenum to ileum and represent a relatively stable cell population, seldom being seen in mitosis; they are present in the small intestine of humans and other primates, ruminants, mice and hamsters, but do not occur in dogs, cats and pigs (Trier and Madara l98l).

Additional Features of the Mucosa

The mucous membrane of the living stomach is grayish pink, except for paler zones at the cardia and pylorus, corresponding to the respective mucosal zones (Bloom and Fawcett l975). The macroscopic, naked-eye assessment of the extent of the pyloric mucosal zone in fresh gastric resection specimens may be quite accurate; according to Dean and Mason (1964); it is said that the pyloric mucosa is flat during life, whereas that of the fornix is rugose. However, naked-eye identification cannot always be regarded as very accurate (Capper et al. 1966). After death the colour turns to a darker grey and the whole membrane becomes softer. Postmortem changes due to autolysis of the mucosa set in rapidly.

In the normal empty, contracted and partially filled stomach, the mucosa is elevated into numerous macroscopic folds or rugae which project into the lumen. Each fold consists of a double layer of mucosa with a central core of submucous tissue. It is said that by virtue of the folds the secretory surface is increased significantly over that of a simple cylinder of similar dimensions (Hendrix 1974). The plication of the mucosa is possible because of the loose consistency of the submucosa and the contractile activity of the muscularis mucosae (Bloom and Fawcett 1975).

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