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