34 [9-1]: Esophagus, light microscopic slide, H&E, 1x lens (slide #62)- In this low magnification view of the esophagus, note that the mucosa consists of a thick (blue staining) stratified squamous non-keratinized lining epithelium supported by a meager lamina propria. The submucosa consists of a loose fibroelastic layer beneath the mucosa. Surrounding this are the inner circular and outer longitudinal muscle layers of the muscularis externa. And finally, the outer most layer is the adventitia, consisting of connective tissue that merges with that of the adjacent tissues and organs [9-2]: Esophagus, light microscopic slide, H&E, 10x lens (slide #62)- This higher magnification view of the esophagus, shows the thick epithelium (stratified squamous, non-keratinized epithelium) resting on a thin lamina propria. The muscularis mucosa is not apparent in this section. [9-3]: Esophagus, light microscopic slide, H&E, 10x lens (slide #62)- This region of the esophagus shows a portion of the muscularis externa (on the right). In this section, this muscle is skeletal in nature, suggesting that this section was taken from the upper 1/3 of the esophagus. Recall that the muscularis externa of the upper 1/3 of the esophagus consists of skeletal muscle, the lower 1/3 consists of smooth muscle and the middle segment contains a mixture of skeletal and smooth muscle. Note the presence of lymphoid tissue (the small lymphocytes) in the lamina propria next to the epithelium. [9-4]: Esophagus, light-microscope slide, H&E, 10x lens (slide #63)- This slide is taken from a different region of the esophagus. Note the thick lining epithelium and the underlying muscularis externa. The muscularis mucosa is not apparent. [9-5]: Esophagus, light-microscope slide, H&E, 10x lens (slide #63)- This region of the esophagus shows the muscularis mucosa. Both skeletal and smooth muscle is apparent suggesting that the section was taken from the middle 1/3 portion of the esophagus. The smooth muscle is present in the upper left of the slide while the skeletal muscle is found on the lower right side. There is a slight difference in the staining characteristics of these muscles; the smooth muscle is more blue while the skeletal muscle is more orange. The smooth muscle contains numerous nuclei that are randomly dispersed, while the skeletal muscle contains fewer nuclei that are located on the periphery of the cell. [9-6]: Esophagus-stomach junction, light-microscopic slide, H&E, 1x lens (slide #64)- In this low magnification view, note the abrupt transition between the very thick stratified epithelium of the esophagus (on the left) and the thin epithelium of the stomach (on the right). Remember that the mucosa of the stomach consists of a thin lining epithelium, a lamina propria that contains the gastric glands and the muscularis mucosa. The dark blue staining region at the boarder is lymphoid tissue. [9-7]: Stomach, fundic, light-microscopic slide, H&E, 1x lens (slide #60)- In this low magnification view of the fundus, identify, muscularis externa (on the bottom), the submucosa, and the mucosa. The section passes tangentially through the mucosa, resulting in the various lengths. Observe the pale-staining cells that line the surface and the pit of the gland. These are the surface-mucous epithelial cells. Note the absence of glands in the submucosa. The muscularis externa usually consists of three layers although only two are shown . The serous is not apparent. [9-8]: Stomach, fundic, light-microscopic slide, H&E, 10x lens (slide #60)- This slide shows a view of the mucosa. Note the pink-staining surface-mucous cells that line the surface and the pits. The mucous neck cells are present in the neck region of the gland, usually adjacent to parietal cells and stain slightly basophilic. The large pink to red staining cells towards the upper part of the mucosa are the parietal cells. Identify the chief or zymogenic cells which predominate in the base of the glands. [9-9]: Stomach, fundic, light-microscopic slide, H&E, 10x lens (slide #56)- This slide shows a different view of the mucosa of the stomach. Here, both the eosinophilic parietal cells can be readily distinguished from the basophilic chief cells that are located at the base of the glands. [9-10]: Stomach, fundic, light-microscopic slide, H&E, 40x lens (slide #56)- A higher magnification view of the base of the glands shows both the parietal and the chief cells. The chief cells contain washed out zymogenic granules and are basophilic due to the presence of rough endoplasmic reticulum (RER) in these cells. Enteroendocrine cells are difficult to demonstrate without special staining. [9-11]: Stomach, cardiac region, light-microscopic slide, H&E, 10x lens- The cardiac glands in this region of the stomach are different from that of the fundic or body region in that there are very few parietal and chief cells. Most of the cells lining the glands are mucous in nature. In contrast to the glands in the pyloric region, in the cardiac region the glands have relatively short pits and the glandular portion is straight. [9-12]: Stomach, pyloric, light-microscopic slide, H&E, 10x lens (slide #66)- In this slide, the mucosa of the pyloric region of stomach is shown. In this region, the length of the gastric pits are usually equal to or greater than the length of the glandular part in this region. The glandular region is convoluted so that many cross sections are apparent. Compare this slide with that of the fundus and the cardiac region. With the exception of a few parietal cells, the epithelium of gastric pits and glands consists of a single mucous cell type. [9-13]: Gesture-duodenal junction, light-microscopic slide, H&E, 1x lens (slide #67)- In this low magnification view, the stomach epithelium is on the left while the duodenum is on the right. There are several dark staining lymphoid nodules in the submucosa of the junction. In the duodenum, note the presence of intestinal villi, the simple columnar lining epithelium, crypts of Lieberkuhn, muscularis mucosa, Brunner's glands and the muscularis externa. [9-14]: Duodenum, light-microscopic slide, H&E, 10x lens (slide #67)- A higher magnification view of the boundary between the mucosa and the submucosa of the duodenum is shown. The red band running across the slide is the muscularis mucosa that defines the boundary of the mucosa. In the submucosa are located Brunner's glands which are a characteristic feature of this portion of the small intestines. These glands secrete a basic solution that helps to neutralize the chyme being released by the stomach. [9-15]: Duodenum, light-microscopic slide, H&E, 1x lens (slide #61)- A low magnification view of the duodenum shows the Brunner's glands located in the submucosa [9-16]: Duodenum, light-microscopic slide, H&E, 10x lens (slide #61)- A higher magnification view of the previous slide shows the junction between the overlying mucosa and the submucosa that contains the Brunner's glands. [9-17]: Jejunum, light-microscopic slide, H&E, 1x lens, (slide #61)- This lows magnification view of the Jejunum shows the intestinal villi, lining epithelium, lamina propria, crypts of Lieberkuhn, muscularis mucosa, submucosa, and the muscularis externa. The jejunum has neither Brunner's glands or Peyer's patches. [9-18]: Jejunum, light-microscopic slide, H&E, 10x lens, (slide #61)- A higher magnification view of the previous slide shows the villi and the crypts of Lieberkuhn. The villi are lined by both goblet cells and the intestinal adsorptive cells. [9-19]: Small intestine, light-microscopic slide, H&E, 1x lens- This slide shows a plica circularis that extends into the lumen of the intestine. a = villus, b = lymphatic nodule, c = submucosa in the plica circularis, d = crypts of Lieberkuhn, e a lymphatic vesicle in the submucosa, f = inner circular layer of the muscularis externa, g = Auerbach's plexus, h = outer longitudinal layer of the muscularis externa, i = serosa, j = mesentery. [9-20]: Ileum, light-microscope slide, H&E, 1x lens- The intestinal villi are relatively short and widely spaced in the ileum. Identify the aggregates of lymph nodules in the lamina propria which are collectively termed Peyer's patches. [9-21]: Ileum, light-microscope slide, H&E, 10x lens- This higher magnification view of a different ileum shows large number of lymphocytes present in the lamina propria. [9-22]: Ileum, light-microscope slide, H&E, 40x lens (slide #74)- This slide shows a view of the base of the crypts of Lieberkuhn. The paneth cells have eosinophilic vesicles in their cytoplasm. [9-23]: Small intestine, scanning electron micrograph, x 250 (#14-6)- In this scanning electron micrograph, note the numerous finger-like intestinal villi. [9-24]: Small intestine, transmission-electron micrograph, x 4,000 (#14-1)- In this transmission electron micrograph of the small intestine, identify the microvillous brush border, nuclei of the intestinal adsorptive cells, connective tissue and blood vessels of the lamina propria. [9-25]: Small intestine, transmission-electron micrograph, x 5,600 (#14-2)- Higher power view of the previous slide shows- microvilli (1), terminal web which is organelle free (2), nuclei of epithelial cells (3) and mitochondria (4). [9-26]: Small intestine, transmission-electron micrograph, x 100,000 (#14-4)- In this thin section of the surface of intestinal adsorptive cells, identify microvilli, the glycocalyx (1), plasmalemma (2), and microfilaments within the core of microvilli (4). [9-27]: Small intestine, transmission-electron micrograph, x 124,000 (#14-3)- In this thin section of the surface of intestinal adsorptive cells, identify, microvilli (1), the glycocalyx (2), a tight junction (3), a desmosome (4), and filaments of the terminal web (6). [9-28]: Mucous goblet cell, transmission-electron micrograph, x 18,000 (#14-5)- In this thin section of the small intestine lining epithelium, identify secretory droplets in the goblet cell, and the microvillous brush border. [9-29]: Large intestine, light-microscopic slide, H&E, 1x lens (slide #60)- There are neither villi nor plicae circularis in the colon. The surface epithelium is simple columnar epithelium which also lines the long tubular intestinal glands. Solitary lymph nodules are often seen in the lamina propria. The outer longitudinal muscle layer is modified to form three bundles of muscle, the taniae coli. Since the teniae are shorter than the other coats of the colon, they case sacculations or periodic bulges called haustra. Between these sacculations, the wall is thrown into crescentic folds, the plicae semilunares. [9-30]: Large intestine, light-microscopic slide, H&E, 10x lens (slide #60)- This higher magnification view of the previous slide shows the mucosa of the colon. Goblet cells are abundant and may constitute most of the lining epithelium. Distinguish between the pink goblet cells and intestinal absorptive cells. [9-31]: Large intestine, light-microscopic slide, H&E, 10x lens (slide #71)- In this section of the colon there is a prominent lymphoid nodule in the mucosa and submucosa. [9-32]: Recto-anal junction, H&E, 1x lens (slide #75)- The rectum is histologically similar to the colon, especially in its upper part. However at its lowest region the mucous membrane has many longitudinal folds, the rectal columns. At the recto-anal junction, the simple columnar epithelium becomes stratified squamous non-keratinized and circular coat of the muscularis is modified as the internal sphincter of the anus. [9-33]: Vermiform appendix, H&E, 1x lens, (slide #73)- The vermiform appendix is a blind fingerlike appendage of the cecum. Large, closely-packed lymph nodules often crowd the lamina propria, partially occluding the lumen. However, in this particular section, the lymphoid is not particularly prominent Because of this concentration of lymphoid tissue, the appendix is sometimes called the "tonsil of the abdomen". The mucous membrane resembles that of the colon. [9-34]: Vermiform appendix, H&E, 10x lens, (slide #74)- This view of the mucosa of the appendix shows the crypts of Lieberkuhn and the surface epithelium contain numerous goblet cells. The lamina propria contains a large number of lymphocytes.