Lecture 7 - Nutrition and the digestion system

Into esophagus many contribung factors 45 vertebrates

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Unformatted text preview: allbladder, pancreas) •  Posterior part func,ons in final diges,on, absorp,on, and elimina,on –  Remainder of small intes,ne and large intes,ne 38 Vertebrates gastrointes,nal system •  Food is chewed in the mouth and mixed with saliva (making bolus) •  Tongue pushed the bolus towards the throat •  Swallowing from pharynx to stomach –  Gravity and peristalsis (smooth muscle contrac,on) 39 Vertebrates gastrointes,nal system  ­ Mouth •  Mouth –  Saliva begins ini,al processing of food –  Moisten and lubricate food to facilitate swallowing –  Dissolve food par,cles to facilitate taste –  Kill ingested bacteria –  Ini,ate diges,on of polysaccharides with amylase 40 Vertebrates gastrointes,nal system •  Pharynx and esophagus –  Pathway to stomach only –  Do not contribute to diges,on or absorp,on –  Swallowing begins in esophagus as voluntary ac,on –  Ac,on con,nues by involuntary peristalsis –  Muscle contrac,on is always proceeded by an,cipatory wave of relaxa,on (moves food only one direc,on) 41 Vertebrates gastrointes,nal system  ­ Stomach •  Stomach –  Store food so it can get digested –  Par,ally digests proteins –  Regulates rate of emptying into small intes,ne –  No lipid or carbohydrate diges,on –  Food reduced to chyme 42 Vertebrates gastrointes,nal system  ­ Stomach •  Types of secretory cells in the stomach –  Hydrochloric acid (HCl): kills ingested microorganisms, dissolves par,culate maaer –  Pepsinogen: converted to pepsin to begin protein diges,on •  Pepsinogen gets converted into pepsin by low pH (high HCl) –  Mucus producing cells help protects stomach cells against pepsin and acid environment 43 Vertebrates gastrointes,nal system  ­ Stomach •  Ulcers –  Places where the mucosal lining of the stomach is damage •  Could lead to indiges,on, gastric bleeding and cancer –  Caused by bacterium –  Marshall, one of the inves,gators, drank a flask of cultured bacteria, caused himself a pre ­ulcerous condi,on and cured this one with an,bio,cs 44 Vertebrates gastrointes,nal system  ­ Stomach •  Heartburn –  1...
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