On slide === Slide 140, Duodenum (PASH):===

1. Observe the plicae circulares at lowest power.

2. Examine the slide to note the numerous villi and occasional solitary lymphatic nodules.

3. With high power, study the epithelium of the villi. Observe the PAS-positive goblet cells and the columnar intestinal absorptive cells with their striated border. The glycoproteins and mucopolysaccharides of the glycocalyx (surface coat) associated with the microvilli (striated border) accounts for the PAS-positive nature of the striated border. The villi contain a connective tissue core, the lamina propria, as described previously.

4. The intestinal glands (= crypts of Lieberkuhn) open between the bases of the villi. The glands extend to the muscularis mucosae. Only a few goblet cells are present in the lower region of the glands. Cells of Paneth are not easily identified; their secretion has been liberated and few or no granules remain. (See slide 139 below.)

5. Beneath the muscularis mucosae the submucosa contains the mucus-secreting, highly branched tubular duodenal glands (= Brunner’s glands, = submucosal glands of the duodenum). The cells of these glands are PAS-positive but the mucin stains less intensely than does the mucin of the goblet cells. The ducts of these glands empty into crypts of Lieberkuhn after they penetrate the muscularis mucosae.

Study slide 139, Duodenum (H&E). (The mucosa is disrupted from post<peir-mortem changes, villi may not be present.)vm>UAB-Histology-00140</peir-vm>

1=== Slide 139, Duodenum (H&E) === (The mucosa is disrupted from post-mortem changes, villi may not be present. ) Observe in favorable areas the straight tubular crypts with the large pyramidal or columnar cells of Paneth at their blind ends. Paneth cells are easily identified by the large acidophilic granules in the apical regions of the cells. The round or oval nucleus is located at the base of the cell.

2. By diligent searching, find an enteroendocrine cell (argentaffin cell) with the orange-staining granules located in an infra-nuclear position, i.e., between the nucleus and the base of the cell. These cells are smaller than Paneth cells and their granules are less coarse. A variety of enzymes are secreted into capillaries by such cells. This slide is excellent for studying duodenal (Brunner’s) glands. Note especially how the ducts open into the crypts.

3. This slide is excellent for studying duodenal (Brunner’s) glands. Note especially how In the ducts open into connective tissue between the cryptstwo muscle layers of the muscularis externa find ganglion cells which belong to the myenteric plexus.

1. The jejunum lacks the submucosal glands of Brunner.

2. On slide === Slide 142, Jejunum (PASH) identify with medium power the villi on the plicae circulares, the villi located in between the plicae circulares, the lamina propria, the intestinal glands (crypts of Lieberkuhn), the submucosa and the muscularis externa.===

3. The Identify with medium power the villi on the plicae circulares, the villi of located in between the plicae circulares, the human jejunum are said to have rounded endslamina propria, but they appear somewhat variable according to the plane intestinal glands (crypts of sectioningLieberkuhn), the submucosa and the muscularis externa.

4. Observe the goblet cells with high power. The nuclei villi of these cells often stain more darkly than the nuclei of adjacent absorptive cells. They human jejunum are also usually narrower or more triangular in shape than in said to have rounded ends, but they appear somewhat variable according to the absorptive cellsplane of sectioning.

5Observe the goblet cells with high power. In favorable regions one can locate The nuclei of these cells often stain more darkly than the PAS-stained basement membrane on which nuclei of adjacent absorptive cells. They are also usually narrower or more triangular in shape than in the epithelial absorptive cells rest.

6. Identify In favorable regions one can locate the striated border and note its reduction or absence on cells at the bases of the crypts of Lieberkuhn. Small apical granules in the gland cells may form a somewhat uniform PAS -stained border, but do not confuse this with a striated border. The gland cells are shorter or less columnar than basement membrane on which the epithelial cells lining the villirest.

ILEUMIdentify the striated border and note its reduction or absence on cells at the bases of the crypts of Lieberkuhn. Small apical granules in the gland cells may form a somewhat uniform PAS stained border, but do not confuse this with a striated border. The gland cells are shorter or less columnar than the cells lining the villi. <peir-vm>UAB-Histology-00142</peir-vm> == Ileum ==

1. === Slide 168, Ileum (H&E). === This is probably from a rhesus monkey; its structure is generally similar to human, but it is small enough in diameter so that a complete cross section can be obtained for study. *Observe most of the features described for duodenum and jejunum. Note especially the several plicae circulares with the core of submucosa extending into them and the muscularis mucosae forming the boundary between mucosa and submucosa as usual. *Paneth cells are not conspicuous (will be seen better in slide 172 below). *Aggregated nodules (Peyer’s patches) form a prominent feature of the ileum. These are aggregates of lymphatic nodules, present in the anti- mesenteric wall of the ileum. They originate in the lamina propria, may extend through the muscularis mucosae into the submucosa. If they reach the lumen of the ileum, they are covered by a layer of cells (called M-cells), not villi. <peir-vm>UAB-Histology-00168</peir-vm>

b. Paneth cells are not conspicuous (will be seen better in slide 172 below)This was removed during surgery and is therefore free of postmortem changes.

c. Aggregated nodules (Peyer’s patches) form a prominent feature *Identify all features of the ileum. These are aggregates of lymphatic nodulesNote, present in the anti- mesenteric wall of the ileum. They originate in the lamina propria, may extend through the muscularis mucosae into the submucosa. If they reach the lumen only a small part of the ileum, they are covered by a layer of cells (called M-cells), not villiPeyer’s patch is present.

2*Study the villi that show typical normal structure. Slide 172, Ileum, human (H&E). This was removed during surgery and The striated border is therefore free of postmortem changesprominent.

a. Identify all features of *Note especially the ileum. NotePaneth cells, only a small part of whose granules stain a Peyer’s patch is presentbrilliant pink.b. Study Also, in the villi that show typical normal structure. The striated border is prominentlamina propria, observe eosinophils containing reddish granules.

c. Note especially the Paneth cells, whose granules stain a brilliant pink. Also, in the lamina propria, observe eosinophils containing reddish granules*Look for submucosal plexuses (Meissner’s) as well as for myenteric plexuses.

1. As a blind diverticulum of the cecum, the appendix has a small and generally irregular lumen. The appendix often exhibits inflammation accompanied by infiltration of large numbers of neutrophils. A constant feature of the appendix is the vast amount of lymphatic tissue present.

2. Scan slide === Slide 145, Appendix (H&E) to find the 4 layers: mucosa, submucosa, muscularis externa, and serosa. The tissue may show postmortem changes and artifacts of preparation.===

3. Note that the appendix lacks villi and plica circulares. The crypts of Lieberkuhn appear similar Scan slide 145, Appendix (H&E) to find the glands of the large intestine4 layers: mucosa, although they may be more variable in length and less numerous per given area. The crypts contain absorptive columnar cellssubmucosa, goblet cellsmuscularis externa, and occasional cells of Paneth and enteroendocrine cells. Find a favorable crypt for study to identify these cell typesserosa. The striated border tissue may show postmortem changes and artifacts of the simple columnar surface cell is thin. The enteroendocrine cells are difficult to identify on our preparations but they are perhaps more numerous in the appendix (5 to 10 per gland) than in the small intestine. Mitotic figures are easily found in the lower ends of the glandspreparation.

4Note that the appendix lacks villi and plica circulares. The lamina propria crypts of Lieberkuhn appear similar to the glands of the large intestine, although they may be more variable in length and less numerous per given area. The crypts contain absorptive columnar cells, goblet cells, and occasional cells of Paneth and enteroendocrine cells. Find a favorable crypt for study to identify these cell types. The striated border of the simple columnar surface cell is completely infiltrated by lymphocytesthin. The enteroendocrine cells are difficult to identify on our preparations but they are perhaps more numerous in the appendix (5 to 10 per gland) than in the small intestine. Note how lymphatic nodules may interrupt Mitotic figures are easily found in the lower ends of the somewhat poorly developed muscularis mucosaeglands.

5. Other prominent cells present here are active macrophages. The “foamy” granulated or vacuolated cytoplasm of these cells stains a darker red than that in other cells of the lamina propriais completely infiltrated by lymphocytes. The smaller cells with bilobed nuclei and reddish cytoplasm are eosinophilsNote how lymphatic nodules may interrupt the somewhat poorly developed muscularis mucosae.

6Other prominent cells present here are active macrophages. Examine slide 146, Appendix (Masson’s stain). No special features are present, but note the blue-stained connective tissue, the myenteric plexus with ganglion The “foamy” granulated or vacuolated cytoplasm of these cells stains a darker red than that in other cells, and of the lymphatic noduleslamina propria. The granules in the smaller cells of Paneth with bilobed nuclei and reddish cytoplasm are darkly stained. Observe that the circular layer of smooth muscle is thicker and better developed than the longitudinal layereosinophils.COLON

2. The straight tubular intestinal glands === Slide 146, Appendix (crypts of LieberkuhnMasson’s stain) are longer and more numerous than in the small intestine, and they contain more numerous mucous goblet cells. Some glands almost appear to consist of goblet cells only. Plicae circulares, villi and Paneth cells are lacking. The mucosa of the human colon therefore has a rather smooth surface. The simple columnar epithelial cells still exhibit a thin absorptive striated border.===

3. The lamina propria of No special features are present, but note the colon is similar to blue-stained connective tissue, the lamina propria of myenteric plexus with ganglion cells, and the small intestine. Lymphocytes are abundant with scattered lymphatic nodules either limited to . The granules in the lamina propria or extending through the muscularis mucosae into the submucosa. Peyer’s patches cells of Paneth are absentdarkly stained. The muscularis mucosae presents two layers Observe that the circular layer of smooth muscle, an inner circular layer, is thicker and an outer better developed than the longitudinal layer.

4. Slide 144 Colon, (PASH, rhesus monkey, complete cross<peir-section, shows three taeniae coli). Scan the slide to see these three taeniae. Mucigen of the goblet cells is very well demonstrated. Study this slide for the features noted above. Find an area where the glands are cut longitudinally to see that they are straight and extend almost to the muscularis mucosae. Study the surface epithelium to see that in some areas more goblet cells appear in the glands than on the luminal surface between glands. Large blood vessels occur in the submucosa. Temporary folds are present. Note that the surface of the mucosa is smooth; the colon lacks villi.vm>UAB-Histology-00146</peir-vm>

5== Colon == In the colon, the 4 layers of the alimentary tract are present, but the longitudinal layer of the muscularis externa is modified to form 3 separate thick longitudinal bands of muscle called the taeniae coli, between which is a thin layer of muscle. The straight tubular intestinal glands (crypts of Lieberkuhn) are longer and more numerous than in the small intestine, and they contain more numerous mucous goblet cells. Some glands almost appear to consist of goblet cells only. Plicae circulares, villi and Paneth cells are lacking. The mucosa of the human colon therefore has a rather smooth surface. The simple columnar epithelial cells still exhibit a thin absorptive striated border. The lamina propria of the colon is similar to the lamina propria of the small intestine. Lymphocytes are abundant with scattered lymphatic nodules either limited to the lamina propria or extending through the muscularis mucosae into the submucosa. Peyer’s patches are absent. The muscularis mucosae presents two layers of smooth muscle, an inner circular layer, and an outer longitudinal layer. === Slide 144 Colon, (PASH, rhesus monkey, complete cross-section, shows three taeniae coli) === Scan the slide to see these three taeniae. Mucigen of the goblet cells is very well demonstrated. Study this slide for the features noted above. Find an area where the glands are cut longitudinally to see that they are straight and extend almost to the muscularis mucosae. Study the surface epithelium to see that in some areas more goblet cells appear in the glands than on the luminal surface between glands. Large blood vessels occur in the submucosa. Temporary folds are present. Note that the surface of the mucosa is smooth; the colon lacks villi. <peir-vm>UAB-Histology-00144</peir-vm> === Slide 180 Colon, (H&E, human, surgical specimen) === Slide 180 Colon, (H&E, human, surgical specimen) is part of a cross-section spread open. One taenia coli is present at one end of the section. No postmortem changes are present. Again study the glands; in longitudinal sections, note their openings into the lumen of the colon and the continuity of their epithelium with the intact surface epithelium. Study other features as above. Serosa (visceral peritoneum) covers the section. 6. <peir-vm>UAB-Histology-00180</peir-vm> === Slide 173 Colon, (H&E, human) === Slide 173 Colon, (H&E, human), is also a cross-section of the colon spread open. Much of the surface epithelium and outer parts of glands are missing, but aside from this, identify features that are listed above. Look for cell bodies of neurons in the submucosal plexuses (of Meissner). Determine if a band of the taenia coli has been sectioned and is present on your slide.RECTUM<peir-vm>UAB-Histology-00173</peir-vm> == Rectum == === Slide 170, Upper Rectum (H&E) === Scan the slide to observe that the longitudinal layer of the muscularis externa forms a continuous layer. Taenia coli are no longer present. Observe that the structure of the upper rectum is similar to that of the colon except for the taenia coli. Identify the layers of the wall and the structures within each layer as in the colon.

b. Observe that the structure of the upper rectum is similar to that of the colon except No slides are available for the taenia coli. Identify the layers study, but you should be aware of the wall and the structures within each layer as some modifications in structure which occur in the colon.lower rectum (upper anal canal)

1. No slides are available for study, but you should be aware *The circular layer of some modifications in structure which occur in smooth muscle becomes thickened to form the lower rectum (upper anal canal)involuntary internal sphincter.

a*Longitudinal (vertical) ridges appear which form the rectal columns (columns of Morgagni or anal columns). They usually overlie small veins that contribute to the formation of internal hemorrhoids. The outer layer Anal valves are transverse folds of smooth muscle is replaced by skeletal muscle that serves as the external anal sphinctermucosa which connect the rectal columns at their bases.

b*The intestinal glands (crypts) become shorter and disappear at the level of the anal valves. Here an abrupt transition leads into the lower anal canal. The circular layer of smooth muscle epithelium becomes thickened to form noncornified, stratified squamous. Near the involuntary internal sphincteranal orifice, the epithelium becomes cornified, highly pigmented and it contains hairs, sebaceous glands and sweat glands.