1. THE DIGESTIVE SYSTEM I D. C. Mikulecky Professor of Physiology Virginia Commonwealth University

2. FUNCTIONS OF THE DIGESTIVE SYSTEM zMOTILITY zSECRETION zDIGESTION zABSORPTION

3. THE DIGESTIVE TRACT zMOUTH AND PHARYNX zESOPHAGUS zSTOMACH zSMALL INTESTINE zLARGE INTESTINE zANUS

4. THE DIGESTIVE TRACT LUMEN MUCOSA SUBMUCOSAL PLEXUS CIRCULAR MUSCLE MYENTERIC PLEXUS LOGITUDINAL MUSCLE EXTRINSIC NERVES

5. INNERVATION OF THE G.I. TRACT zPARASYMPATHETIC zSYMPATHETIC zINTRINSIC

6. PARASYMPATHETIC zVAGUS: DOWN TO TRANSVERSE COLON. PREGANGLIONIC CHOLINERGIC NEURONS ORIGNINATE IN MEDULLA zPELVIC: BELOW THAT. PREGANGLIONIC CHOLINERGIC NEURONS ORIGNINATE IN SACRAL S.C.

7. SYMPATHETIC zGANGLIA OUTSDE G. I. TRACT: CELIAC, SUPERIOR AND INFERIOR MESENTERIC zPOSTGANGLIONIC ADRENERGIC FIBERS INNERVATE MYENTERIC AND SUBMUCOSAL PLEXUS

8. INTRINSIC INNERVATION zSUBMUCOSAL PLEXUS zMYENTERIC PLEXUS zDIFFERENT MEDIATORS: ACh, Nitric Oxide, VIP, Enkephalins, Serotonin, Substance P

9. G. I. PEPTIDES zHORMONES zNEUROCRINES zPARACRINES

10. G. I. HORMONES zGASTRIN zCHOLECYSTOKININ (CCK) zSECRETIN zGIP zMOTILIN

11. GASTRIN zENDOCRINE CELLS IN PYLORIC STOMACH zSTIMULATED BY PROTEIN IN STOMACH zSTIMULATES SECRETION BY PARIETAL AND CHIEF CELLS zSTIMULATES ILEAL MOTILITY zRELAXES ILEOCECAL SPHINCTER zINDUCES COLONIC MASS MOVEMENTS

12. SECRETIN zENDOCRINE CELLS IN DUODENAL MUCOSA zACID IN DUODENAL LUMEN zINHIBITS GASTRIC EMPTYING zINHIBITS GASTRIC SECRETION zSTIMULATES AQUEOUS BICARBONATE SECRETION BY PANCREAS zSTIMULATES BICARBONATE RICH BILE SECRETION BYLIVER

13. CHOLECYSTOKININ zENDOCRINE CELLS IN DUODENAL MUCOSA zFAT AND PROTEIN IN DUODENAL LUMEN zINHIBITS GASTRIC EMPTYING zINHIBITS GASTRIC SECRETION zCAUSES GALL BLADDER CONTRACTION zCAUSES RELAXATION OF THE SPHINCTER OF ODDI zCONTRIBUTES TO SATIETY

14. GASRTIC INHIBITORY PEPTIDE (GIP) zSTRUCTURALLY RELATED TO SECRETIN AND GLUCAGON zINHIBITS GASTRIC ACIS SECRETION (PHARMACOLOGICAL DOSES) zSTIMULATES INSULIN RELEASE

15. MOTILITY zTHE DIGESTIVE TRACT IS SURROUNDED BY LAYERS OF SMOOTH MUSCLE zTHESE MUSCLES ENABLE MIXING AND PROPULSIVE MOVEMENT TO BE CARRIED OUT BY THE DIGESTIVE TRACT

16. SECRETION zDIGESTION REQUIRES THAT ENZYMES BE SECRETED BY THE PANCREAS AND OTHER ORGANS zMUCOUS SECRETIONS PROTECT THE DIGESTIVE TRACT zACID IS SECRETED IN THE STOMACH zTHERE ARE OTHER SECRETIONS OF IMPORTANCE

17. DIGESTION zBREAKING DOWN COMPLEX FOODSTUFFS INTO ABSORBABLE UNITS BY ENZYMES PRODUCED IN THE DIGESTIVE SYSTEM zINVOLVES THE BREAKDOWN OF CARBOHYDRATES, PROTEINS FATS, AND OTHER FOODS

18. ABSORPTION zALL OTHER FUNCTIONS SUPPORT THIS ONE zTHIS IS HOW WE OBTAIN THE NECESSARY FUEL FOR OUR CELLS

19. ACCESSORY DIGESTIVE ORGANS zSALIVARY GLANDS zEXOCRINE PANCREAS zBILLIARY SYSTEM: (LIVER AND GALLBLADDER)

20. CONTROL OF DIGESTIVE SYSTEM External Influences Local Influences Receptors in Digestive Tract Intrinsic Nerve Plexuses Extrinsic Autonomic Nerves GI Hormones Smooth muscle Exocrine Gland Cells Endocrine Gland Cells

21. THE MOUTH zINGESTION OF FOOD zCHEWING AND SWALLOWING zSALIVARY SECRETION

22. CHEWING zCHEWING IS THE FIRST STEP IN THE DIGESTIVE PROCESS zFOOD IS MIXED WITH SALIVA AND BROKEN UP INTO SMALLER PIECES zTASTE BUDS ARE STIMULATED

23. SALIVARY SECRETION zSALIVARY AMYLASE: DIGESTS CARBOHYDRATE zMOISTENING AND LUBRICATING AGENT zANTIBACTERIAL ACTION: LYSOZYME AND RINSING zSOLVENT FOR TASTE STIMULI zSPEECH FACILITATION zORAL HYGENE zBICARBONATE BUFFERS NEUTRALIZE ACIDS

24. Swallowing zA PROGRAMMED ALL-OR-NONE REFLEX zCHEWING AND MOVING THE BOLUS OF FOOD BACK IS MANLY VOLUNTARY (STRIATED MUSCLE) zPRESSURE OF BOLUS ON PHARYNX TRIGGERS INVOLUNTARY REFLEX (SMOOTH MUSCLE) zTONGUE PREVENTS FOOD FROM MOVING BACK zUVULA ELEVATED, SEALING NASAL PASSAGE zLARYNX ELEVATES AND CLOSURE OF GLOTTIS zRESPIRATION BRIEFLY INHIBITED zPHARYNGEAL MUSCLES FORCE BOLUS BACK zPERISTALTIC WAVES MOVE BOLUS THROUGH ESOPHAGUS

25. PERISTALSIS RINGLIKE CONTRACTION SWEEPS DOWN THE ESOPHAGUS

26. THE STOMACH ESOPHAGUS BODY ANTRUM GASTROESOPHAGEAL SPHINCTER PYLORIC SPHINCTER OXYNTIC MUCOSA PYLORIC GLAND AREA FUNDUS

27. THE STOMACH zMIXING AND STORAGE ORGAN zHAS ITS OWN PACEMAKER: SETS FREQUENCY OF RHYTHMIC PERISTALTIC CONTRACTIONS zPERISTALSIS BECOMES STRONGER IN ANTRUM zMOTILITY IS HIGHLY CONTROLLED zNO ABSORPTION OF FOOD, ONLY ASPIRIN AND ALCOHOL

28. FACTORS INFLUENCING GASTRIC MOTILITY zDISTENSION OF STOMACH: INCREASES zFEEDBACK FROM THE SMALL INTESTINE: DECREASES zCONTROL FROM CNS zGASTRIN: INCREASES

29. MIXING MOTIONS IN THE STOMACH PYLORIC SPHINCTER CLOSED PERISTALSIS BEGINS

30. MIXING MOTIONS IN THE STOMACH PYLORIC SPHINCTER CLOSED PERISTALTIC WAVE TRAVELS DOWNWARD

31. STOMACH EMPTYING PYLORIC SPHINCTER OPENS PERISTALTIC WAVE TRAVELS DOWNWARD CHYME SQUIRTED INTO DUODENUM

32. FACTORS CONTROLLING STOMAC EMPTYING zGASTRIC MOTILITY zENTEROGASTRIC REFLEX: VIA INTRINSIC AND AUTONOMIC NERVES zENTEROGASTRONES: SECRETIN, CHOLECYSTOKININ (CCK), GASTRIC INHIBITORY PEPTIDE

33. FACTORS IN SMALL INTESTINE CONTROLLING STOMAC EMPTYING zFAT zACID zHYPERTONICITY zDISTENSION

34. GASTRIC SECRETIONS zMUCOUS: SURFACE CELLS z MUCOUS: MUCOUS NECK CELLS zHYDROCHLORIC ACID: PARIETAL CELLS zINTRINSIC FACTOR: PARIETAL CELLS zPEPSINOGEN: CHIEF CELLS zGASTRIN: ONLY IN THE PYLORIC GLAND AREA

35. ACTIVATION OF PEPSIN CHIEF CELL PEPSIN-OGEN HCL PARIETAL CELL PEPSIN DIGESTS PROTEIN

36. STIMULATION OF GASTRIC SECRETION: CEPHALIC PHASE SEEING, SMELLING, TASTING FOOD VAGUS INTRINSIC NERVES PYLORIC AREA PARIETAL & CHIEF CELLS GASTRIN INCREASED GASTRIC SECRETION

37. STIMULATION OF GASTRIC SECRETION: GASTRIC PHASE STIMULI IN STOMACH: PROTEIN, DISTENSION, CAFFEINE, ALCOHOL VAGUS INTRINSIC NERVES PYLORIC AREA PARIETAL & CHIEF CELLS GASTRIN INCREASED GASTRIC SECRETION

38. THE GASTRIC MUCOSAL BARRIER zPROTECTS THE CELLS FROM CONTENTS OF STOMACH zLUMINAL MEMBRANES OF CELLS ARE IMPERMEABLE TO PROTONS zCELLS ARE TIGHTLY ADJOINED zRAPID TURNOVER zIF BROKEN, PEPTIC ULCER MAY RESULT: POSITIVE FEEDBACK INVOLVING HISTAMINE

39. GASTRIN SECRETION INHIBITION zACID IN ANTRUM zREMOVAL OF PROTEIN AS STOMACH EMPTIES