1. Physiology Lecture: 46 Gastrointestinal Physiology
Tanveer Raza MD MS MBBS

3. Movement in GIT Propulsive movements or Peristalsis Mixing movements
Moves food forward along GIT at an appropriate rate for digestion and absorption
Mixing movements
Keeps intestinal contents thoroughly mixed at all times
Tanveer Raza MD MS MBBS

4. Movement in GIT: Peristalsis
Requires active myenteric plexus
Congenital absence of myenteric plexus
Peristalsis is depressed or absent
Atropine (paralyzes cholinergic nerve endings)
Directional movement toward Anus
Can occur in either direction but normally occurs towards anus
Tanveer Raza MD MS MBBS

5. Movement in GIT: Peristalsis
Tanveer Raza MD MS MBBS

6. Movement in GIT: Mixing Movement
Differs in different parts
Peristaltic contractions causing mixing
Occurs when forward progression is blocked by sphincter. Peristaltic wave can then only churn the contents, rather than propelling them
Local intermittent constrictive contractions
Tanveer Raza MD MS MBBS

7. Movement in GIT: Mixing Movement
Differs in different parts
Peristaltic contractions causing mixing
Local intermittent constrictive contractions
Occurs every few centimeters in gut wall. Usually last only 5-30 seconds; then new constrictions occur at other points, "chopping" & "shearing" the contents first here and then there
Tanveer Raza MD MS MBBS

8. Movement in GIT: Mixing Movement
Tanveer Raza MD MS MBBS

9. Gastrointestinal Reflexes: 3 types
Integrated entirely within the gut wall enteric nervous system
Gut to prevertebral sympathetic ganglia and then back to GIT
Gut to the spinal cord or brain stem and then back to the GIT
Tanveer Raza MD MS MBBS

10. Gastrointestinal Reflexes
Tanveer Raza MD MS MBBS

11. Gastrointestinal Reflexes: 3 types
Integrated entirely within the gut wall enteric nervous system
Much GI secretion
Peristaltic reflex
Mixing contractions
Local inhibitory effects
Gut to prevertebral sympathetic ganglia and then back to GIT
Gut to the spinal cord or brain stem and then back to the GIT
Tanveer Raza MD MS MBBS

12. Gastrointestinal Reflexes: 3 types
Integrated entirely within the gut wall enteric nervous system
Gut to prevertebral sympathetic ganglia and then back to GIT
Reflexes transmit signals long distances to other areas of GIT
Gastrocolic reflex
Enterogastric reflex
Colonoileal reflex
From gut to the spinal cord or brain stem and then back to the GIT
Tanveer Raza MD MS MBBS

13. Gastrointestinal Reflexes: 3 types
Integrated entirely within the gut wall enteric nervous system
Gut to prevertebral sympathetic ganglia and then back to GIT
Gastrocolic reflex
From stomach, causes colon evacuation
Defecation after meal is rule for children
In adults, habits and culture play a rule
Maybe due to action of gastrin acting on colon, not neurally mediated
Gut to the spinal cord or brain stem and then back to the GIT
Tanveer Raza MD MS MBBS

14. Gastrointestinal Reflexes: 3 types
Gastrocolic reflex may affect Irritable Bowel Syndrome (IBS) or spastic colon
Tanveer Raza MD MS MBBS

17. Gastrointestinal Reflexes: 3 types
Gut to prevertebral sympathetic ganglia and back to GIT
Enterogastric reflex
From colon and small intestine, inhibits stomach motility and secretion
Initiated by
Product of protein digestion hydrogen ions bathing the duodenal mucosa
Duodenal distention
Tanveer Raza MD MS MBBS

18. Gastrointestinal Reflexes: 3 types
Integrated entirely within the gut wall enteric nervous system
Gut to prevertebral sympathetic ganglia and then back to GIT
Colonoileal reflex
From colon, inhibits emptying of ileal contents into colon
Gut to the spinal cord or brain stem and then back to the GIT
Tanveer Raza MD MS MBBS

19. Gastrointestinal Reflexes: 3 types
Integrated entirely within the gut wall enteric nervous system
Gut to prevertebral sympathetic ganglia and then back to GIT
Gut to the spinal cord or brain stem and then back to the GIT
Reflexes controlling gastric motor and secretory activity
Pain reflexes
Defecation reflexes
Tanveer Raza MD MS MBBS

20. Gastrointestinal Reflexes: 3 types
Gut to the spinal cord or brain stem and then back to the GIT
Reflexes controlling gastric motor and secretory activity
From stomach and duodenum to brain stem and back to stomach-by way of vagus nerves
Tanveer Raza MD MS MBBS

21. Gastrointestinal Reflexes: 3 types
Gut to the spinal cord or brain stem and then back to the GIT
Pain reflexes
General inhibition of the entire GIT
Defecation reflexes
From colon and rectum to spinal cord and back again to produce the powerful colonic, rectal, and abdominal contractions required for defecation
Tanveer Raza MD MS MBBS

22. CHEWING (MASTICATION)
Tanveer Raza MD MS MBBS

23. Mastication: Chewing reflex
Chewing is a reflex action
Voluntarily chewing can occur
Tongue and to a lesser extent lips and cheeks acts to keep food between the grinding surfaces of teeth
Tanveer Raza MD MS MBBS

24. Mastication: Chewing reflex
Food in mouth
Reflex inhibition of lower jaw muscles.
Lower jaw drops
Stretch reflex causes muscle contraction
Closure of mouth
Tanveer Raza MD MS MBBS

25. Mastication: Importance
Breaks indigestible cellulose membrane
Fruits and raw vegetables
Breaks large pieces into small pieces
 surface area for digestive enzymes to work
Breaks food into very fine particulate and mixes with salivary secretion
Tanveer Raza MD MS MBBS

26. Mastication: Importance
Breaks indigestible cellulose membrane
Breaks large pieces into small pieces
Breaks food into very fine particulate and mixes with salivary secretion
Helps in deglutition and digestion
Prevents excoriation of GIT
Eases passage of food
Tanveer Raza MD MS MBBS

27. SWALLOWING

28. Sword Swallowing: Lessons
Tanveer Raza MD MS MBBS

29. Sword Swallowing: Lessons
Tanveer Raza MD MS MBBS

30. Sword Swallowing: Lessons
Tanveer Raza MD MS MBBS

31. Swallowing: Stages Voluntary Stage Involuntary Stage Pharyngeal stage
Initiates Swallowing process
Involuntary Stage
Pharyngeal stage
Esophageal stage
Tanveer Raza MD MS MBBS

32. Swallowing: Voluntary Stage
Food ready for swallowing
“Voluntarily" squeezed or rolled posteriorly into pharynx by pressure of the tongue upward and backward against the palate
From here on, swallowing normally cannot be stopped
Tanveer Raza MD MS MBBS

33. Swallowing: Stages Involuntary Stage Pharyngeal stage Esophageal stage
Passage of food through pharynx into esophagus
In less than 6 seconds
Esophageal stage
Tanveer Raza MD MS MBBS

34. Swallowing: Pharyngeal Stage
Tanveer Raza MD MS MBBS

35. Swallowing: Pharyngeal Stage
Once food bolus reaches pharynx several actions are initiated:
Closure of Nasal Aperture
Closure of Trachea
Swinging back of Epiglottis
Opening of Esophagus
Tanveer Raza MD MS MBBS

36. Swallowing: Pharyngeal Stage of Swallowing Animation (Must go to Slide show to see animation)
Tanveer Raza MD MS MBBS

37. Swallowing: Pharyngeal Stage
Closure of nasal aperture
Soft palate is pulled upward to close the posterior nares
Tanveer Raza MD MS MBBS

38. Swallowing: Pharyngeal Stage
Closure of the trachea
Vocal cords are strongly approximated
Larynx is pulled upward and anteriorly by the neck muscles
Swinging back of epiglottis
Tanveer Raza MD MS MBBS

39. Swallowing: Pharyngeal Stage
Closure of the trachea
Vocal cords are strongly approximated
Most important
Destruction of vocal cords or the muscles that approximate them can cause strangulation
Tanveer Raza MD MS MBBS

40. Swallowing: Pharyngeal Stage
Closure of the trachea
Larynx is pulled upward and anteriorly by the neck muscles
Upward movement also lifts glottis out of main stream of food flow, so food passes on each side of epiglottis rather than over its surface. Protects against entry of food into trachea
Tanveer Raza MD MS MBBS

41. Swallowing: Pharyngeal Stage
Closure of the trachea
Swinging back of epiglottis
Epiglottis swing backward over the opening of the larynx
Tanveer Raza MD MS MBBS

42. Swallowing: Pharyngeal stage
Opening of esophagus
Upward movement of larynx pulls up and enlarges the esophageal opening.
The upper esophageal sphincter (also called the pharyngoesophageal sphincter) relaxes
Tanveer Raza MD MS MBBS

43. Swallowing: Stages Involuntary Stage Esophageal stage
Pharyngeal stage
Esophageal stage
Transport of food from pharynx to stomach
Tanveer Raza MD MS MBBS

44. Thank You