The rectangular area in figure below is considered at higher magnification here. It shows how the epithelium of the stomach differs from that of the intestine. In both cases, the epithelium is simple columnar, and the underlying lamina propria (LP ) is highly cellular because of the presence of large numbers of lymphocytes. The boundary between gastric and duodenal epithelium is marked by
The submucosa of the duodenum contains submucosal (Brunner’s) glands. These are below the muscularis mucosae; therefore, this structure serves as a useful landmark in identifying the glands. In the stomach, the muscularis mucosae is readily identified as narrow bands of muscular tissue (MM ). It can be followed toward the right into the duodenum but is then interrupted in the region between the two asterisks.
This figure also shows the thickened region of the gastric muscularis externa, where the stomach ends. This is the pyloric sphincter (PS ). Its thickness, mostly due to the amplification of the circular layer of smooth muscle of the muscularis externa, can be appreciated by comparison with the muscularis externa in the duodenum (ME ).
gastric pits. The boundary between the pits and glands is, however, hard to ascertain in H&E sections.
With respect to the mucosal aspects of gastroduodenal histology, as mentioned above, the glands of the stomach empty into gastric pits. These are depressions; accordingly, when the pits are sectioned in a plane that is oblique or at right angles to the long axis of the pit, as in this figure, the pits can be recognized as being depressions because they are surrounded by lamina propria. In contrast, the inner surface of the small intestine has villi (V). These are projections into the lumen of slightly varying height. When the villus is cross-sectioned or obliquely sectioned, it is surrounded by space of the lumen, as is one of the villi shown here. In addition, the villi have lamina propria (LP ) in their core.
the arrow. On the stomach side of the arrow, the epithelium consists of surface mucous cells (SMC). The surface cells contain an apical cup of mucous material that typically appears empty in an H&E–stained paraffin section. In contrast, the absorptive cells (AC ) of the intestine do not possess mucus in their cytoplasm. Although goblet cells are found in the intestinal epithelium and are scattered among the absorptive cells, they do not form a complete mucous sheet. The intestinal absorptive cells also possess a striated border, which is shown in Plate 60.
PLATE 58KEY AC, absorptive cells BGl, Brunner’s glands D, ducts IGl, intestinal glands IMuc, intestinal mucosa LP, lamina propria ME, muscularis externa MM, muscularis mucosae PGl, pyloric glands PMuc, pyloric mucosa PS, pyloric sphincter SMC, surface mucous cells V, villi arrows: bottom figure, Brunner’s gland element that passes from the submucosa to the mucosa; upper right figure, boundary between gastric and duodenal epithelium asterisks, interruption in muscularis mucosae