PSIO 202 University of Arizona Histology Slides Digestive System Case Discussion

PSIO 202

University of Arizona


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PSIO 202 Required Handout Department of Physiology Histology Slides Digestive System *Students are required to know all the bold terms included in this handout Slide 1: Esophagus (longitudinal section) • Stratified squamous epithelium forms the most superficial layer of the organ. • In the esophagus, there is relatively little lamina propria, and it is very difficult to distinguish the connective tissue of the lamina propria from that of the submucosa. This is true of this particular slide. Within the connective tissue that underlies the epithelium, you can see small sections of muscle tissue which represent the muscularis mucosae. The submucosa of the esophagus also contains mucus secreting glands, which although not depicted in this slide, are present along most of the length of the esophagus. • The third and outermost layer shown in the slide is the inner circular layer of the muscularis externa. Since this is a longitudinal section of the esophagus, the orientation of the circular layer looks different compared to a cross section through the alimentary canal. Slide 2: Esophagus (longitudinal section) • Stratified squamous epithelium forms the most superficial layer of the organ (stained pink). • The lamina propria and submucosa lies just deep to the epithelium (stained blue). Recall that it is difficult to distinguish the lamina propria from the submucosa in the esophagus. Small sections of muscle tissue within the connective tissue represent the muscularis mucosae (stained pink). • The third layer in the slide (stained pink) is the inner circular layer of the muscularis externa. Slide 3: Stomach (longitudinal section) • This slide depicts three general layers of the stomach wall. The innermost layer, the mucosa, is stained dark pink and appears highly cellular. Deep to this layer is the loosely arranged connective tissue of the submucosa, followed by two portions of the muscularis externa (inner circular and outer longitudinal). • Notice the arrangement of the mucosal epithelium. At higher magnification you will be able to discern gastric pits and glands. This is one of the key features that distinguishes the stomach from the rest of the GI tract. Slide 4: Stomach (higher magnification—depicts gastric pits) • The mucosal epithelium of the stomach is organized into gastric pits and glands. Notice the simple columnar epithelium and how it is invaginated at regular intervals. The invaginations are the gastric pits. The simple columnar cells lining the gastric pits secrete mucus into the stomach lumen. • At the base of the gastric pits are many cells that collectively form gastric glands. The gastric pits act as ducts for the materials that are secreted by these cells. • Notice the lamina propria that extends between the epithelium. Slide 5: Stomach (better view of gastric pits) • This slide illustrates the gastric pits, lined by simple columnar epithelium, the lamina propria extending between the epithelium, and the gastric glands that lie below the pits. If you look closely you should also be able to see very thin sections of muscle tissue extending between the epithelium—this represents the muscularis mucosae. • Notice the cells that make up the gastric glands. In this slide the majority of cells are large and stain light-pink. These are the parietal cells that secrete H+ and Cl- into the gastric pits and stomach lumen. PSIO 202 Required Handout Department of Physiology Slide 6: Stomach (depicts the base of the gastric glands) • At the base of the gastric glands the majority of cells are chief cells. These cells are smaller than parietal cells and stain blue to purple in color. They secrete pepsinogen, a precursor enzyme of protein digestion. Slide 7: Small intestine (cross section) • This slide depicts three general layers of the small intestine. The mucosa is stained bright blue, the submucosa is light gray in color and contains clusters of glands, and the outer muscularis externa layers (inner circular and outer longitudinal) are blue-gray in color. • Notice that the mucosal epithelium has both extensions and invaginations. The extensions are called villi, and they are lined by simple columnar epithelium with goblet cells interspersed. Note that in this slide mucin, a component of mucus, stains red. The invaginations of the epithelium are called intestinal glands or crypts of Lieberkuhn. The simple columnar cells of the crypts participate mainly in absorption, although some secrete mucus or other chemicals that aid digestion (hormones, lyzozyme). Although it is difficult to see in this section, the lamina propria and muscularis mucosae typically extend between the villi in the small intestine. Slide 8: Small intestine (depicts villi and a plica circularis) • Notice how the tissue in the slide appears folded. The gross anatomy of the small intestinal mucosa forms folds called the plicae circularis. Histologically, the epithelium of the mucosa then forms invaginations and extensions (the crypts and villi). • Notice that the lamina propria is easier to see in this slide, extending up between the villi. Also note the muscularis mucosa that lies at the base of the mucosa and also extends up in small portions between the villi (the muscle tissue is stained bright blue). • Deep to the muscularis mucosae you can see the submucosa. Slide 9: Villus of the small intestine • This slide shows a villus at a higher magnification. Notice the simple columnar epithelium lining the villus, and the lamina propria extending within the interior of the villus. Within the lamina propria notice the capillary containing red blood cells. Slide 10: Large intestine (longitudinal section) • This slide illustrates the mucosa and submucosa of the large intestine. Notice that the epithelium of the large intestine has invaginations like the small intestine, but lacks villi. Like the small intestine, the invaginations here are called crypts of Lieberkuhn, and are made up of simple columnar epithelium with goblet cells interspersed. The number of goblet cells is greater in the large intestine compared to the small intestine. • Note the lamina propria between the glandular epithelium and the muscularis mucosae (stained pink) at the base of the mucosal layer. Deep to the muscularis mucosae is the submucosa, which is loosely arranged and stained very light pink. Slide 11: Salivary gland • This slide illustrates the two secretory cell types contained within salivary glands—mucus and acini (serous) cells. The mucus cells, stained white in this slide, secrete mucus, and the acini cells, stained purple with a grainy appearance, secrete salivary amylase, an enzyme found in saliva. • Also note the salivary ducts in the slide, formed by simple cuboidal epithelium (stained light pink). These ducts move the mucus and salivary amylase into the oral cavity. PSIO 202 Required Handout Department of Physiology Slide 12: Pancreas • The pancreas contains an endocrine and exocrine component. The endocrine component contains cells that secrete hormones including insulin and glucagon. These cells appear in clusters called pancreatic islets (islets of Langerhans), the lighter staining central region of this slide. • The other cells in the pancreas are exocrine cells that secrete precursor enzymes into the small intestine to aid digestion. These cells are called serous or acini cells and are stained darker in color (dark pink or purple) than the endocrine cells described above. Slide 13: Liver lobule • The liver is organized into lobules which contain hepatocytes (liver cells stained pink here) arranged around a central vein (shown here in the center of the slide). Each lobule is separated from the next by connective tissue, shown in dark blue. • At the corners of the lobule are portal triads, regions that contain a branch of the hepatic portal vein, a branch of the hepatic artery, and a bile duct (you can distinguish each of these structures at higher magnification). Venous blood from the small intestine enters the liver lobule via the hepatic portal vein branch and then filters through sinusoids, small spaces between the hepatocytes. The hepatocytes process this blood before it drains into the central vein to exit the liver. Similarly, arterial blood to oxygenate the hepatocytes enters the lobule via the hepatic artery branch, and flows through the sinusoids en route to the central vein. • Bile formed by hepatocytes moves in the direction opposite of blood, toward the bile ducts in the portal triads via small bile canals (not identifiable in the slide). Slide 14: Portal triad This slide depicts a portal triad at higher magnification. The hepatic portal vein branch has the largest lumen, very thin walls and contains red blood cells. The hepatic artery branch has a smaller lumen, a thick muscular wall, and also contains red blood cells. The bile duct is lined by simple cuboidal epithelium. Notice the other vessels in the area—these are either lymphatic vessels or smaller blood venules. • PSIO 202 CASE STUDY INTRODUCTION Initial Case Study Presentation and Assignment 1: Spring 2020 DUE Friday March 27 Robert is a single, 20-year-old, Caucasian male. He has a moderately active lifestyle. He walks his dog every day and enjoys hiking on the weekend. He is an animal lover and has recently transitioned from a vegetarian diet to a strict vegan diet in the last 18 months. As a sophomore at the University of Arizona, majoring in pharmaceutical science, he spends most of his time studying for PSIO 202 and organic chemistry. He recently began dating his PSIO lab partner, Valentina, who is also vegan. They enjoy cooking together and eat most of their meals at home. On Saturday, Robert went for his usual walk, but began to feel fatigued and breathless after just half a mile. He attributed it to having only eaten a salad that day and made a note to eat more protein, although he dislikes most meat substitutes. After a good night’s sleep and a large breakfast, Robert decided to go on a hike with Valentina in the morning. He struggled for most of the hike even though it was light terrain. About halfway through the hike he began feeling some tingling in his fingers and numbness in his feet. He was not too concerned, because he was breaking in new hiking boots and had been swinging his arms a lot throughout the hike. However, after tripping repeatedly and struggling to navigate the trail, Robert decided that they should turn back early. That following week, Valentina noticed that her usually fun-loving, boisterous boyfriend seemed to be growing more and more moody, depressed, and tired. These changes, along with Robert’s occasional complaint of numbness and tingling, lead Valentina to suggest that Robert see his PCP, so he made an appointment for the next day. Assignment 1: Diagnostic Test Recommendation DUE Fri March 27 Based on the information presented in the scenario above, choose 2 diagnostic tests or scans that you would recommend be performed on Robert. Briefly describe the tests/scans and explain what information each could give you about Robert’s condition. Each student needs to complete the assignment individually. The assignment needs to be put in the corresponding dropbox under the Assignments tab in D2L by Friday March 27 at 11:59 pm. You must cite at least 1 credible reference (not Wikipedia or WebMD) for each test or scan mentioned using APA. Be sure to include in-text citations (No citations = No credit). No late assignments will be accepted. ...
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Final Answer




Physiology Class


Physiology Class

Robert is a vegan together with his girlfriend. During the usual walk, he also reported
fatigue and breathlessness after a short walk. They reported having gone for a hike where he
struggled a lot to finish it. Robert also reports being consuming more proteins. Besides, during
the hike, he felt some tingling feelings fingers and numbness in the feet. He also reported having
noticed a change that was associated wit...

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