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DIGESTIVE PHYSIOLOGY

DIGESTIVE PHYSIOLOGY. PHYSIOLOGICAL PROCESSES. MECHANICAL PROCESSES SECRETION CHEMICAL DIGESTION ABSORPTION. MECHANICAL PROCESSES. MOVEMENT PATTERNS. SEGMENTATION. STATIONARY MUSCULAR CONTRACTIONS DIVIDES GI TRACT INTO CONSTRICTED OR UNCONSTRICTED SECTIONS. PERISTALSIS.

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DIGESTIVE PHYSIOLOGY

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  1. DIGESTIVE PHYSIOLOGY

  2. PHYSIOLOGICAL PROCESSES • MECHANICAL PROCESSES • SECRETION • CHEMICAL DIGESTION • ABSORPTION

  3. MECHANICAL PROCESSES MOVEMENT PATTERNS

  4. SEGMENTATION • STATIONARY MUSCULAR CONTRACTIONS • DIVIDES GI TRACT INTO CONSTRICTED OR UNCONSTRICTED SECTIONS

  5. PERISTALSIS • WAVE LIKE CONTRACTION • FORCES MATERIALS TO MOVE BEFORE IT • NORMALLY MOVES TOWARD ANUS • PROBABLY DUE TO INTRINSIC NERVE PLEXUS

  6. CHEWING • MASTICATION • FORMS BOLUS • REDUCES FOOD INTO SMALLER PIECES THAT ARE EASIER TO DIGEST

  7. SWALLOWING • MOVES BOLUS FROM MOUTH TO STOMACH • INITIATED BY TONGUE ON ROOF OF MOUTH • PRESSURE RECEPTORS AT OPENING OF PHARYNX INITIATE SWALLOWING REFLEX

  8. SWALLOWING REFLEX • PHARYGEAL CONSTRICTOR MUSCLES • PERISTALTIC CONTRACTION

  9. UPPER ESOPHAGEAL SPHINCTER • KEEPS ESOPHAGUS CLOSED

  10. EPIGLOTTIS • WITH VOCAL CORDS KEEP FOOD FROM GOING INTO TRACHEA • COUGHING REMOVES FOOD THAT DOES GET INTO TRACHEA

  11. MOVEMENT ALONG THE ESOPHAGUS • PERISTALTIC CONTRACTIONS • TUNICA MUSCULARIS

  12. LOWER ESOPHAGEAL SPHINCTER • 2-5 CM ABOVE CARDIAC ORIFICE • KEEPS OPENING TO STOMACH CLOSED • FOOD GENERALLY TAKES ABOUT 5 -10 SECONDS TO REACH STOMACH

  13. GASTRIC MOTILITY

  14. MECHANICAL ACTIVITIES OF STOMACH • STORING FOOD • MIXING FOOD WITH GASTRIC SECRETIONS • MOVEMENT OF FOOD INTO DUODENUM

  15. STOMACH VOLUME • ABOUT 50 ML NORMALLY • CAN EXPAND TO TO 1000-1500ML • WILL NOT HAVE AN INCREASE IN PRESSURE • DUE TO SMOOTH MUSCLE ABILITY TO LENGTHEN WITHOUT INCREASING TENSION • ALSO DUE TO RECEPTIVE RELAXATION

  16. CHYME • SEMIFLUID MIXTURE OF FOOD AND GASTRIC SECRETIONS

  17. PYLORIC SPHINCTER • USUALLY PARTIALLY OPEN • OFFERS ONLY LIMITED RESISTANCE

  18. STOMACH MUSCLE CONTRACTIONS • BEGIN IN BODY • MOVE TOWARD PYLORIC SPHINCTER • INCREASE IN STRENGTH AND SPEED IN LOWER REGIONS • FORCES CHYME OUT OF STOMACH INTO DUODENUM • MATERIAL LEFT OVER REBOUNDS BACK INTO STOMACH

  19. PACESETTER CELLS • SLOW WAVE POTENTIALS • GIVES SMOOTH MUSCLE A BASIC ELECTICAL RHYTHM • THREE CYCLES PER MINUTE CYCLES

  20. FACTORS THAT INFLUENCE MEMBRANE POTENTIALS • MECHANICAL • HORMONAL • NEURAL

  21. MECHANICAL FACTORS • VOLUME OF STOMACH • MECHANORECEPTORS INTIATE REFLEXES TO INCREASE GASTRIC MOTILITY RELAXATION OF PYLORIC SPHINCTER PROMOTION OF GASTRIC EMPTYING • BOTH LONG AND SHORT REFLEXES INVOLVED

  22. SHORT REFLEXES • NEURAL SIGNALS ORIGINATE FROM WALL OF DIGESTIVE TRACT • TRANSMITTED BY INTRINSIC NERVE PLEXUSES TO EFFECTOR CELLS • ALL ELEMENTS ARE LOCATED IN DIGESTIVE TRACT WALL

  23. LONG REFLEXES • AFFERENT IMPULSES TO BRAIN CENTERS • EFFERENT IMPULSE TO INTRINSIC PLEXUSES AND EFFECTOR CELLS OF DIGESTIVE SYSTEM

  24. HORMONAL FACTORS • GASTRIN

  25. EFFECT OF VOLUME AND COMPOSITION OF CHYME ENTERING DUODENUM • EXERTS MAJOR EFFECT ON GASTRIC MOTILITY • EXERTS MAJOR EFFECT ON GASTRIC EMPTYING • EXERTS BOTH HORMONAL AND NEURAL CONTROL

  26. ENTEROGASTRIC REFLEX • WHEN DUODENUM FILLS WITH CHYME • DISTENSION OF WALL • INHIBITS GASTRIC MOTILITY • INCREASES CONTRACTION OF PYLORIC SPHINCTER

  27. ENTEROGASTERONES • COLLECTION OF HORMONES • RELEASED IN RESPONSE TO ACID CHYME • PRESENCE OF FAT • PRESENCE OF CERTAIN AMINO ACIDS • INHIBIT GASTRIC MOTILITY AND SLOW GASTRIC EMPTYING

  28. ENTEROGASTERONES • SECRETIN • MAYBE CCK AND GIP

  29. NET EFFECT • TO SLOW MOVEMENT OF CHYME UNTIL SMALL INTESTINE HAS PROCESSED WHAT IT ALREADY HAS

  30. SMALL INTESTINE MOTILTY

  31. SEGMENTATION • MAJOR MOVEMENT • MOST COMMON MOVEMENT DURING MEAL • QUITE ACTIVE JUST AFTER MEAL • LITTLE OCCURS BETWEEN MEALS • MIXES CHYME WITH DIGESTIVE JUICES • INCREASES EXPOSURE TO MUCOSA

  32. SMOOTH MUSCLE • HAS BASIC ELECTRICAL RHYTHM • DETERMINES FREQUENCY OF SEGMENTATION CONTRACTIONS • RATE VARIES THROUGHOUT SMALL INTESTINE • GREATEST SEGMENTATION IN UPPR PART • LEAST IN LOWER PART

  33. FACTORS THAT AFFECT SEGMENTATION • MECHANICAL • NEURAL • HORMONAL

  34. MIGRATING MOTILITY COMPLEX • SERIES OF WEAK PERISTALTIC CONTRACTIONS • BEGINS AT DUODENUM • NEW WAVES CONTINUE THROUGHOUT SMALL INTESTINE • 100-150 MINUTES

  35. ILEOCECAL SPHINCTER • CONTROLS MOVEMENT OF MATERIALS INTO CECUM • MATERIAL IN CECUM INTIATES INTRINSIC NERVE PLEXUS TO STIMULATE SPHINCTER • USUALLY MILDLY CONSTRICTED • ALLOWS TIME FOR ABSORPTION

  36. GASTROILEAL COMPLEX • REFLEX THAT INCREASES ILEAL CONTACTION • OCCURS WHEN FOOD ENTERS STOMACH

  37. GASTRIN • INCREASE MOTILITY IN ILEUM • RELAXES ILEOCECAL SPHINCTER • INCREASES MOVEMENT INTO CECUM • ALLOWS ROOM IN STOMACH FOR MORE FOOD

  38. ILEOCECAL VALVE • FOLDS OF TISSUE • PROTECTS OPENING OF ILEUM INTO CECUM • PREVENTS BACK FLOW

  39. LARGE INTESTINE MOTILITY • SLUGGISH • 18-24 HOURS FOR MOVEMENT THROUGH

  40. SEGMENTATION • LOWER RATE THAN IN SMALL INTESTINE • CALLED HAUSTRAL CONTACTIONS • MAY OCCUR EVERY THIRTY MINUTES OR SO

  41. MASS MOVEMENTS • OCCUR THREE OR FOUR TIMES PER DAY • LARGE SEGMENTS OF COLON EXPERIENCE STRONG CONTRACTIONS • MOVE CONTENTS FOR LONG STRETCHES • OFTEN OCCUR AFTER MEALS

  42. FACTORS THAT MAY INTITIATE MASS MOVEMENTS • DUODENUM MAY INTITIATE DUODENOCOLIC REFLEX • STOMACH MAY INTITIATE GASTROCOLIC REFLEX • NET EFFECT IS TO MAKE ROOM FOR MORE FOOD

  43. DEFECATION REFLEX • MOVES MATERIAL OUT OF LOWER COLON AND RECTUM • TRANSMITTED BY INTRINSIC PLEXUS • REINFORCED BY INPUT FROM SACRAL REGION

  44. EFFECTS OF DEFECATION REFLEX • SIGMOID COLON AND RECTUM CONTRACT • INTERNAL ANAL SPHINCTER RELAXES • FECES PROPELLED INTO ANUS • EXTERNAL ANAL SPHINCTER DETERMINES WHETHER IT WILL LEAVE

  45. ACTIVITIES THAT ASSIST THE DEFECATION REFLEX • DEEP INSPIRATION • HOLDING BREATH • CONTRACTING ABDOMINAL MUSCLES • THESE ACTIVITIES RAISE ABDOMINAL PRESSURE

  46. SECRETORY ACTIVITIES OF GI TRACT

  47. ORAL REGION • PAROTID GLAND • SUBLINGUAL GLAND • SUBMANDIBULAR GLAND • BUCCAL GLAND

  48. TYPES OF SALIVA • MUCOUS SECRETION • SEROUS SECRETION

  49. PAROTID GLAND • SEROUS SECRETIONS

  50. SUBMANDIBULAR GLAND • SEROUS

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