BIOLOGY 238 Unit 2b Objectives

Digestive System

1. Define the following and describe their importance to the digestive system: ingestion, mastication, deglutition, propulsion, secretion, absorption, digestion (physical and chemical), exfoliation, defecation.

2. Identify the location and structural composition of the alimentary canal.

3. Describe the structure, arrangement, and functions of the recurring layers of the alimentary canal and associated peritoneal cavity. Include: fibroserous covering (serosa or fibrous adventitia), muscularis (longitudinal, transverse or circular, oblique), submucosa, mucosa, muscularis mucosae. Terms: columnar epithelium, goblet cells and other mucus secreting cells (mucus neck cells, mucus surface cells), visceral peritoneum, parietal peritoneum, mesentery, greater and lesser omentum, lamina propria.

4. Distinguish between mechanical (physical) and chemical digestion and identify the objects or substrate of each and the products.

5. Describe the important structures and functions related to digestion of the oral cavity and the important histological differences between it and other portions of the alimentary canal.

Terms: hard and soft palates, uvula, non-keratinized stratified squamous epithelium, salivary glands (parotid, submandibular, sublingual, buccal), saliva, salivary amylase, bolus, mastication, deglutition.

6. Differentiate between the buccal phase and the pharyngeal-esophageal phases of swallowing. Describe the roles of the uvula, epiglottis, and muscles of swallowing.

7.. Describe control of salivary secretion by cephalic and physical contact mechanisms. Terms: pressoreceptors, chemoreceptors.

8. Describe the structure, location and function related to digestion of the pharynx and compare histologically to other areas of the alimentary canal.

9. Describe the structure, location and function of the esophagus and compare it histologically to other areas of the alimentary canal. Terms: esophageal glands, gastroesophageal (cardiac) region, hiatal hernia.

10. Describe the process of motility or propulsion and the role of the longitudinal and transverse smooth muscle layers in segmentation and peristalsis.   Terms: gap junctions, pacemaker cells, cyclic slow waves, basic electrical rhythm (BER).

11. Describe the roles of the intrinsic nerve plexuses in controlling secretion and motility in the alimentary canal. Terms: submucosal plexus, myenteric plexus.

12. Describe the structure, location and function related to digestion of the stomach and compare histologically to other areas of the alimentary canal. Include: fundus, body, pylorus, pyloric sphincter, muscularis (circular, longitudinal, oblique), rugae, mucosa, gastric pits, zymogen (chief) cells, parietal cells, mucous neck cells, mucus surface cells, enteroendocrine cells, pepsinogen, pepsin, role of H⁺, chyme, intrinsic factor, gastrin, histamine, anti-histamine, retropulsion.

13. Describe the mechanisms which normally act to protect the GI lining from destruction by acid secretion. Terms: peptic ulcer (gastric, duodenal), exfoliation, alkaline mucus, Brunner's glands, helicobacter pylori.

14. Describe the mechanisms of gastric control and HCL secretion including: cephalic, gastric phase, intestinal phase. Terms: hypothalamus-vagus connection, physical contact, gastrin, gastric inhibiting peptide (GIP), enterogastrones, secretin, CCK, enterogastric reflex.

15. Identify and compare the portions of the small intestine as to locations, structure (including histology), and functions related to digestion. Terms: duodenum, ileum, jejunum, ileocecal sphincter, hepatopancreatic ampulla, sphincter of Oddi.

16. Identify the enzymes and other secretions released into the small intestine, their sources, functions, substrates, required conditions, and the endproducts or results of their actions. Include: pancreatic juice (trypsin, chymotrypsin, lipase, amylase, carboxypeptidase), intestinal enzymes (aminopeptidase, carboxypeptidase, sucrase, maltase, lactase, enterokinase), bile, bicarbonate, enterokinase.

17. Describe the functions of secretin and cholecystokinin (CCK) in regulating processing by the small intestine.

18. Identify the functions of the small intestine and the structural components, including histology which contribute to the performance of these functions. Include: villi, plicae circularis (circular folds), intestinal glands (crypts of Lieberkuhn) microvilli (brush border), goblet cells, enteroendocrine cells, Peyer's patches, Brunner's glands, lacteals, capillary network, muscularis mucosae.

19. Describe the structure and functions of the large intestine (colon) and rectum and mechanisms involved in the production of the feces and defecation. Include: teniae coli, haustra, cecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, ileocecal sphincter, internal and external anal sphincters, haustral churning, peristalsis, mass peristalsis, gastrocolic and gastroileal reflexes, defecation reflex.

20. Describe the mechanisms for absorption of digestive endproducts and other materials and where absorption occurs. Include: water, salts and electrolytes, monosaccharides and other carbohydrates, glycerol, fatty acids and neutral fats, amino acids and polypeptides, active cotransport, facilitated diffusion, endocytosis, exocytosis, micelles, chylomicrons.