L43_NPB_101 - Lecture 43 •  SmartSite: – ...

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Unformatted text preview: Lecture 43 •  SmartSite: –  Lecture 43 Notes •  GastrointesRnal System –  Basic Anatomy –  Structure & FuncRon of GI Organs •  Announcements: –  UCD Bookstore Textbook Buyback –  Sherwood $96.50 (7th ed) –  See Flyer next slide •  Reading (Recommended): –  Ch 16 (pg. 588 ­638) 1 2 GastrointesRnal (DigesRve) System •  Primary funcRon –  Transfer nutrients, water, and electrolytes from ingested food into body’s internal environment •  Four funcRons –  MoRlity –  SecreRon –  DigesRon –  AbsorpRon 3 DigesRve System •  MoRlity –  Muscular contracRons that mix and move forward the contents of the digesRve tract –  Two types of digesRve moRlity •  Propulsive movements –  Push contents forward through the digesRve tract •  Mixing movements –  Serve two funcRons »  Mixing food with digesRve juices promotes digesRon of foods »  Facilitates absorpRon by exposing all parts of intesRnal contents to absorbing surfaces of digesRve tract 4 DigesRve System •  DigesRve secreRons –  Consist of water, electrolytes, and specific organic consRtuents –  SecreRons are released into digesRve tract lumen on appropriate neural or hormonal sRmulaRon –  Normally reabsorbed in one form or another back into blood a_er their parRcipaRon in digesRon 5 DigesRve System •  DigesRon –  Biochemical breakdown of structurally complex foodstuffs into smaller, absorbable units –  Accomplished by enzymaRc hydrolysis –  Complex foodstuffs and their absorbable units •  Carbohydrates → monosaccharides •  Proteins → amino acids •  Fats → glycerol and facy acids 6 Polysaccharide DigesRon Yields Absorbable Carbohydrates Category of foodstuffs Carbohydrates Polysaccharides (starch and glycogens) Maltose Monosaccharides (glucose, galactose, fructose) Intermediate Breakdown of Products End Products of Digestion Absorbable Units Amylase Disaccharides Sucrose Maltase Sucrase Lactose Lactase See Table 16 ­6; pg. 624 7 Protein DigesRon Yields Amino Acids See Table 16 ­6; pg. 624 8 Fat DigesRon Yields Monoglycerides and Free Facy Acids Fats Monoglyceride Triglyceride Free fatty acids Lipase See Table 16 ­6; pg. 624 9 DigesRve System •  AbsorpRon –  In the small intesRne, most absorpRon is complete –  Small units resulRng from digesRon, along with water, vitamins, and electrolytes are transferred from digesRve tract lumen into blood or lymph 10 DigesRve System Components •  DigesRve tract •  •  •  •  •  –  ConRnuous from mouth to anus –  Consists of Mouth Pharynx Esophagus Stomach Small intesRne •  Accessory digesRve organs –  Salivary glands –  Exocrine pancreas –  Biliary system •  Liver •  Gallbladder –  Duodenum –  Jejunum –  Ileum –  –  –  –  Cecum Appendix Colon Rectum •  Large intesRne •  Anus 11 Gross Anatomy of the Human GI Tract See Table 16 ­1; pg. 582 ­3 12 Gross Anatomy of the Human GI Tract See Table 16 ­1; pg. 582 ­3 13 DigesRve Tract •  Wall has same general structure throughout length from esophagus to anus •  Four major Rssue layers –  Mucosa •  Innermost layer –  Submucosa –  Muscularis externa –  Serosa •  Outer layer Fig. 16 ­2; pg. 594 14 Mucosa •  Lines luminal surface of digesRve tract •  Highly folded surface greatly increases absorpRve area •  Three layers –  Mucous membrane •  Serves as protecRve surface •  Modified for secreRon and absorpRon •  Contains –  Exocrine gland cells – secrete digesRve juices –  Endocrine gland cells – secrete blood ­borne gastrointesRnal hormones –  Epithelial cells – specialized for absorbing digesRve nutrients –  Lamina propria •  Houses gut ­associated lymphoid Rssue (GALT) •  Sparse layer of smooth muscle –  Important in defense against disease ­causing intesRnal bacteria –  Muscularis mucosa 17 Submucosa •  Thick layer of connecRve Rssue •  Provides digesRve tract with distensibility and elasRcity •  Contains larger blood and lymph vessels •  Contains nerve network known as submucosal plexus 18 Muscularis Externa •  Major smooth muscle coat of digesRve tube •  In most areas consists of two layers –  Circular layer •  Inner layer •  ContracRon decreases diameter of lumen •  Outer layer •  ContracRon shortens the tube –  Longitudinal layer •  ContracRle acRvity produces propulsive and mixing movements •  Myenteric plexus –  Lies between the two muscle layers 19 Serosa •  Secretes serous fluid –  Lubricates and prevents fricRon between digesRve organs and surrounding viscera •  ConRnuous with mesentery throughout much of the tract –  Acachment provides relaRve fixaRon –  Supports digesRve organs in proper place while allowing them freedom for mixing and propulsive movements 20 DigesRve System FuncRon •  DigesRve moRlity and secreRon are regulated by –  Autonomous smooth muscle funcRon –  Intrinsic nerve plexuses –  Extrinsic nerves –  GastrointesRnal hormones 21 Summary of Pathways Controlling DigesRve System AcRviRes Fig. 16 ­3; pg. 596 22 Swallowing •  Coordinated muscle contracRons •  Food enters GI passages •  Close off respiratory passages Fig. 16 ­5; pg. 599 23 ContracRons Move Food Through the Esophagus •  Peristalsis •  Generally moves food in one direcRon Fig. 16 ­6; pg. 600 24 Swallowing hcp://www.nature.com/gimo/contents/pt1/images/gimo13 ­v1.mov 25 ...
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This note was uploaded on 11/07/2010 for the course NPB NPB 101 taught by Professor Weidner/wingfield during the Spring '08 term at UC Davis.

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