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Digestion 1

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Digestion 1

  1. 1. GASTROINTESTINAL TRACT (GIT) . [ DR.PRATIK KUMAR CHATTERJEE (MBBS;MD;FAGE) ASSISTANT-PROFESSOR DEPARTMENT OF PHYSIOLOGY KASTURBA MEDICAL COLLEGE (KMC) MANGALORE KARNATAKA ; INDIA ] .
  2. 2.  TOPICS TO BE COVERED :- (i). FUNCTIONAL ANATOMY . (ii). SALIVARY GLAND . (iii). OESOPHAGUS . (iv). STOMACH . (v). GASTRO-INTESTINAL (GI) MOTILITY . (vi). LIVER .
  3. 3. (vii). PANCREAS . (viii). INTESTINE . (ix). DIGESTION & ABSORPTION . (x). GASTRO-INTESTINAL (GI) HORMONES .
  4. 4. [I]. FUNCTIONAL ANATOMY .
  5. 5. <ul><li> TOPICS FOR TODAY :- </li></ul><ul><li>[I]. INTRODUCTION . </li></ul><ul><li>[II]. PROCESSES . </li></ul><ul><li>[III]. FUNCTIONS . </li></ul>
  6. 6. <ul><li>[IV]. COMPONENTS . </li></ul><ul><li>[V]. HISTOLOGY . </li></ul><ul><li>[VI]. INNERVATION . </li></ul><ul><li>[VII]. MOVEMENTS IN GIT </li></ul><ul><li>(FUNCTIONAL TYPES) </li></ul>
  7. 7. <ul><li>[I]. INTRODUCTION :- </li></ul><ul><li>(i). Provides the body with the </li></ul><ul><li>continuous supply of water ; </li></ul><ul><li>electrolytes & nutrients . </li></ul>
  8. 8.  GASTROINTESTINAL (GI) SYSTEM .
  9. 9. <ul><li>[II]. PROCESSES :- </li></ul><ul><li>(i). MOVEMENT  food through the </li></ul><ul><li>alimentary tract . </li></ul><ul><li>(ii). SECRETION  digestive juices . </li></ul><ul><li>(iii). ABSORPTION  water ; various </li></ul><ul><li>electrolytes & digestive products . </li></ul>
  10. 10. <ul><li>(iv). CIRCULATION  blood through the </li></ul><ul><li>gastrointestinal organs to carry </li></ul><ul><li>away the absorbed substances . </li></ul><ul><li>(v). CONTROL  functions by </li></ul><ul><li>local ; nervous & hormonal </li></ul><ul><li>systems . </li></ul>
  11. 11. <ul><ul><li>[III]. FUNCTIONS :- </li></ul></ul><ul><ul><li>(i). DIGESTION  ingested food into </li></ul></ul><ul><ul><li>absorbable molecules . </li></ul></ul><ul><ul><li>(ii). SECRETION  salivary glands ; </li></ul></ul><ul><ul><li>pancreas & liver (GI lumen) . </li></ul></ul>
  12. 12. <ul><ul><li>(iii). ABSORPTION  nutrients ; </li></ul></ul><ul><ul><li>electrolytes & water from </li></ul></ul><ul><ul><li>intestinal lumen into the </li></ul></ul><ul><ul><li>blood stream . </li></ul></ul><ul><ul><li>(iv). MOTILITY  propels ingested </li></ul></ul><ul><ul><li>food from mouth to rectum ; </li></ul></ul><ul><ul><li>mixes & reduces the size of </li></ul></ul><ul><ul><li>food . </li></ul></ul>
  13. 14. <ul><li>[ IV]. COMPONENTS :- </li></ul><ul><li>(i). MOUTH . </li></ul><ul><li>(ii). PHARYNX . </li></ul><ul><li>(iii). ESOPHAGUS . </li></ul><ul><li>(iv). STOMACH . </li></ul><ul><li>(v). SMALL INTESTINE . </li></ul><ul><li>(vi). LARGE INTESTINE . </li></ul>
  14. 16. <ul><li>(vii). ACCESSORY ORGANS & STRUCTURES :- </li></ul><ul><li>Salivary glands . </li></ul><ul><li>Tongue . </li></ul><ul><li>Liver . </li></ul><ul><li>Gall bladder . </li></ul><ul><li> Pancreas . </li></ul>
  15. 18. [V]. HISTOLOGY .
  16. 19. (1). POSTERIOR PHARYNX TO ANUS :- <ul><li>[i]. SEROUS LAYER (SEROSA) :- </li></ul><ul><li>Attachment of the gut to the surrounding </li></ul><ul><li>structures . </li></ul><ul><li>[ii]. LONGITUDINAL SMOOTH MUSCLE </li></ul><ul><li>LAYER . </li></ul>
  17. 20. <ul><li>[iii]. CIRCULAR SMOOTH MUSCLE </li></ul><ul><li>LAYER :- </li></ul><ul><li>Mixing & propulsion of contents of the </li></ul><ul><li>gut . </li></ul><ul><li>[iv]. SUBMUCOSAL LAYER :- </li></ul><ul><li>Loose connective tissue ; blood vessels & </li></ul><ul><li>lymphatics . </li></ul><ul><li>[v]. MUCOSAL LAYER :- </li></ul><ul><li>Glands ; muscularis mucosa of the </li></ul><ul><li>smooth muscle ; loose connective tissue  </li></ul><ul><li> in lymphocytes . </li></ul><ul><li>Mucosa </li></ul><ul><li>Smooth muscle </li></ul><ul><li>Lamina propria </li></ul><ul><li>Innermost epithelial cell layer </li></ul>
  18. 21. HISTOLOGY OF THE GIT
  19. 22. <ul><li>(2). FEATURES :- </li></ul><ul><li>[i]. Plain muscle & non-striated . </li></ul><ul><li>[ii]. Involuntary . </li></ul>
  20. 23. <ul><li>[iii]. SINGLE UNIT SMOOTH MUSCLE :- </li></ul><ul><li>(A). Aggregated into sheets or bundles . </li></ul><ul><li>(B). Syncytial smooth muscle . </li></ul><ul><li>(C). Gap junctions . </li></ul>
  21. 25. <ul><li>[iv]. FACTORS THAT DEPOLARIZE </li></ul><ul><li>THE MEMBRANE :- </li></ul><ul><li>(A). Stretching of the muscle . </li></ul><ul><li>(B). Stimulation by acetylcholine . </li></ul><ul><li>(C). (+) parasympathetic nerves that </li></ul><ul><li>secrete acetylcholine . </li></ul><ul><li>(D). (+) specific GIT hormones . </li></ul>
  22. 26. <ul><li>[v]. FACTORS THAT HYPERPOLARIZE </li></ul><ul><li>THE MEMBRANE :- </li></ul><ul><li>(A). The effect of norepinephrine / </li></ul><ul><li>epinephrine on the fiber </li></ul><ul><li>membrane . </li></ul><ul><li>(B). (+) sympathetic nerves that secrete </li></ul><ul><li>mainly norepinephrine . </li></ul>
  23. 28. [VI]. MECHANISM OF CONTRACTION & RELAXATION :- <ul><li>(A). Smooth muscle doesn’t contain </li></ul><ul><li>troponin . </li></ul><ul><li>(B). Calmodulin acts as regulatory </li></ul><ul><li>protein . </li></ul><ul><li>(C). Myosin kinase & myosin </li></ul><ul><li>phosphatase play a major role . </li></ul>
  24. 29. Influx of Ca2+ from ECF 4 Ca2 + ions bind to calmodulin Ca2+-calmodulin complex Activates myosin kinase Myosin kinase with ATP phosphorylates Regulatory chain of myosin head Myosin head develops Binding capacity Cycle of attachment & Detachment- contraction
  25. 30. Reduced Ca2+ levels Activation of myosin phosphatase Dephosphorylation of Regulatory light chain Attachment-detachment Cycle stops Relaxation
  26. 31. [VI]. INNERVATION :-
  27. 32. <ul><li>(i). ENTERIC NERVOUS SYSTEM :- </li></ul><ul><li>(1). LOCATION :- </li></ul><ul><li> Entirely in the wall of </li></ul><ul><li>the gut (esophagus – anus) . </li></ul><ul><li>(2). NETWORK OF FIBERS (2 TYPES) :- </li></ul><ul><li>[A]. INTRINSIC INNERVATION . </li></ul><ul><li>[B]. EXTRINSIC INNERVATION . </li></ul>
  28. 34. (ii). INTRINSIC INNERVATION :-
  29. 35. <ul><li>[1]. TYPES (2) :- </li></ul><ul><li> MYENTRIC PLEXUS / AUERBACH’S </li></ul><ul><li>PLEXUS . </li></ul><ul><li> SUBMUCOSAL PLEXUS / </li></ul><ul><li>MEISSNER’S PLEXUS . </li></ul>
  30. 36. [2]. LOCATION :- -
  31. 37. <ul><li>[3]. (+) MYENTRIC PLEXUS :- </li></ul><ul><li>Increased tonic contraction / tone of the </li></ul><ul><li>gut wall . </li></ul><ul><li>Increased intensity of the rhythmical </li></ul><ul><li>contractions . </li></ul><ul><li>Slightly increased rate of rhythm of </li></ul><ul><li>contractions . </li></ul><ul><li>Increased velocity of conduction of </li></ul><ul><li>excitatory waves along the gut wall (rapid </li></ul><ul><li>movement) . </li></ul>
  32. 38. <ul><li>[4]. SIGNIFICANCE :- </li></ul><ul><li>(a). MYENTRIC PLEXUS / AUERBACH’S </li></ul><ul><li>PLEXUS  motor in function (mainly) . </li></ul><ul><li>(b). SUBMUCOSAL PLEXUS / </li></ul><ul><li>MEISSNER’S PLEXUS  sensory in </li></ul><ul><li>function (mainly) . </li></ul><ul><li>(c). CONTROL :- </li></ul><ul><li> Both plexus are interconnected & under </li></ul><ul><li>extrinsic nervous control . </li></ul>
  33. 39. (iii). EXTRINSIC INNERVATION :-
  34. 40. <ul><li>[1]. SYMPATHETIC NERVE FIBERS :- </li></ul><ul><li>(a). Preganglionic sympathetic fibers </li></ul><ul><li>arise from lateral horns of spinal </li></ul><ul><li>cord between T-5 & L-2 segments . </li></ul><ul><li>(b). Terminate in celiac & mesenteric </li></ul><ul><li>ganglia . </li></ul><ul><li>(c). Postganglionic fibers are distributed </li></ul><ul><li>throughout the GIT . </li></ul><ul><li>(d). (+)  motility ; tone ; secretions </li></ul><ul><li>(stomach) & relaxation of sphincters . </li></ul>
  35. 42. <ul><li>[2]. PARASYMPATHETIC NERVE FIBERS :- </li></ul><ul><li>(a). Pass through cranial & sacral nerves . </li></ul><ul><li>(b). Synapse with the postganglionic nerve </li></ul><ul><li>cells in the myentric & submucosal </li></ul><ul><li>plexus . </li></ul><ul><li>(c). (+)  motility ; tone ; secretions </li></ul><ul><li>(stomach) & constrictions of the </li></ul><ul><li>sphincters . </li></ul>
  36. 44. <ul><li>[VII]. MOVMENTS IN THE GIT </li></ul><ul><li>(FUNCTIONAL TYPES) :- </li></ul><ul><li>(1). PERISTALSIS  propulsive movements . </li></ul><ul><li>(2). MIXING  segmentation movements . </li></ul>
  37. 46. <ul><li>THANK YOU . </li></ul>

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