GI Secretions - Dr. Kennon M. Garrett GI-24...

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Unformatted text preview: Dr. Kennon M. Garrett GI-24 GASTROINTESTINAL SECRETION Learning Objectives 1. List the components and functions of saliva. 2. Describe the regulation of salivary secretion. 3. List the types and function of cells in the stomach. 4. Describe the mechanism and regulation of acid secretion in the stomach during the cephalic, gastric and intestinal phases. 5. Describe the function of intrinsic factor. 6. Describe the mechanism of pepsinogen secretion and activation. 7. List functions of mucus. 8. List the composition and functions of pancreatic secretions. 9. Describe the regulation of pancreatic secretions. 10. Describe the composition of bile salts and the regulation of its release. 11. Describe the enterohepatic circulation of bile salts. 12. Describe the formation and elimination of bilirubin. 13. List the composition of gall stones. Dr. Kennon M. Garrett GI-25 I. Salivary secretion A. Functions of saliva 1. Protection a. Antibacterial- lysozyme, lactoferrin. b. Neutralize acid - bicarbonate neutralizes acid secreted by bacteria in mouth c. Lubrication - water and mucus d. Xerostomia inability to produce saliva Sjgren Syndrome - autoimmune disease that destroys salivary and lacrimal glands 2. Digestion Salivary amylase begins digestion of carbohydrates B. Secretion of Saliva Saliva is secreted by a variety of salivary glands (parotid, sublingual, submandibular and minor salivary glands). The basic unit of the salivary glands is the sa1ivon that consists of acinar cells and duct cells . 1. Acinar cells secrete the organic components of saliva along with a fluid that has approximately the same ionic composition as plasma. As the saliva passes down the duct its composition is altered by duct cells. K + Cl- Na + HCO 3- H 2 O Cl- Na + K + HCO 3- Acinar cells Salivon Duct cells Dr. Kennon M. Garrett GI-26 2. Duct cells absorb Na + and Cl- out of the fluid and secrete K + and HCO 3- into it. The saliva that enters the oral cavity is hypotonic to plasma and contains higher concentrations of K + and HCO 3- and lower concentrations of Na + and Cl- than plasma. C. Control 1. 1-2 liters of saliva secreted each day 2. Stimulated by thought of food, smell, mechanical stimulation of oral mucosa, taste (acid) 3. Stimulation is mediated entirely by neural mechanisms a. Parasympathetic - cholinergic stimulation of secretion & vasodilatation of vessels to salivary gland. Parasympathetic stimulation is the most important control of salivary secretion. b. Sympathetic - small, transient stimulation of salivation 1. II. Gastric secretion of HCl A. Gastric Glands (oxyntic glands) - found in body of the stomach 1. Surface epithelial cells secrete thick mucus and bicarbonate 2. Mucous neck cells secrete thin mucus 3. Parietal cells (oxyntic cells) secrete HCl and intrinsic factor 4. Chief cells secrete pepsinogen 5. Enterochromaffin-like-cells (ECL cells) secrete histamine 6. D cells secrete somatostatin Dr. Kennon M. Garrett GI-27 B. Functions of HCl...
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This note was uploaded on 10/01/2011 for the course PSYO 5016 taught by Professor Staff during the Fall '11 term at The University of Oklahoma.

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GI Secretions - Dr. Kennon M. Garrett GI-24...

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