12 - GRQ- Digestive System PDF

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Guided reading questions Digestive System This GRQs document is divided into two sections: 1. Introduction to the digestive system 2. Regulation of gastric activity + Liver Follow the course schedule to learn which section you need to complete and when Section I: Introduction to the digestive system Read pages 851-856. Do not hesitate to use the web when a question is not specifically addressed in the textbook.

1. Define the following in your own words: Ingestion- _____________________________________________________ Digestion- _____________________________________________________ Absorption- _____________________________________________________ Compaction- _____________________________________________________ Defecation- _____________________________________________________

2. Compare and contrast mechanical and chemical digestion

3. What type of digestion takes place in our mouth, and by which components of the digestive system?

A comment on the opening paragraph in p. 851: While the author uses the terms “alimentary canal” and “gastrointestinal (GI)/digestive tract” as interchangeable terms, it is noteworthy that some sources would distinguish between the two and would define the GI tract as only containing the stomach and intestines 4. What are the accessory organs of the digestive system?

5. What do some scientists mean when stating “In the strict sense, defecated food was never in the body”?

6. Our digestive system is open to the environment, including many pathogens. What would expect to find along the intestines, to prevent these pathogens form getting into our blood?

7. What are the main functions of the mesenteries?

8. What are the main functions of the mucosa? The submucosa?

9. Figure 22.3 shows the main anatomical features of the digestive tract wall, using the esophagus as an example. The diagram below depicts a cross section from another part of the digestive tract. Match the words below to the proper positions on the diagram. Note that not all the positions on the diagram (and the corresponding lines) match the word bank, so some lines will stay empty.

Submucosa Mucosa Longitudinal muscular layer Circular muscular layer Serosa Epithelial layer Muscularis mucosae

Section II: Regulation of gastric activity + Liver For regulation of gastric activity, read pages 868-870 For the liver, read pages 881-884 Do not hesitate to use the web when a question is not specifically addressed in the textbook.

Pages 868-870 Start with the “Regulation of gastric function” sub-section. As you read about each phase, follow figure 22.12

1. Describe each of the three phases of gastric activity in one sentence Cephalic Phase

Gastric Phase

Intestinal Phase

2. Which nervous system is the major player in regulation of gastric activity?

3. What are the two major factors that stimulate gastric secretion during the gastric phase?

4. Which hormone is secreted by the G cells as a result of this stimulation, and what are the target cells of this hormone? 5. What factors comprise the negative feedback loop that takes place during the gastric phase?

6. What factors comprise the positive feedback loop that takes place during the gastric phase?

7. The intestinal phase mostly involves inhibition of gastric secretion and motility. What is the rationale behind this inhibition?

8. Secretin, GIP, and CCK are stimulated by __________ and inhibit gastric activity and emptying by affecting gastric _______ as well as by stimulating the ________________ 9. Do the three phases of gastric activity take place at different times or can they work simultaneously? Pages 881-884 Read about the liver, but you are not responsible for the anatomical and histological details of the liver. We will focus here on the physiological functions of the liver 10. Describe in two sentences each of the functions of the liver

11. Give one example of nutrient storage that is taking place in the liver

12. On p. 883, under “Nutrient Metabolism”, the author mentions the fact that the liver is responsible for synthesizing the plasma proteins (e.g. albumin). From our discussions about the lymphatic system, how does plasma protein synthesis affect the volume of interstitial fluid in our body? (hint: consider the “lost and found” role of the lymphatic system)...