Digestive Physiology Physiological functions of the mouth,pharynx & oesophagus By: M.H.Dashti...

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Digestive Physiology Digestive Physiology Physiological functions Physiological functions of the mouth ,pharynx & of the mouth ,pharynx & oesophagus oesophagus y: M.H.Dashti Lecture 3
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Transcript of Digestive Physiology Physiological functions of the mouth,pharynx & oesophagus By: M.H.Dashti...

  • Slide 1
  • Digestive Physiology Physiological functions of the mouth,pharynx & oesophagus By: M.H.Dashti Lecture 3
  • Slide 2
  • Digestion in the Mouth Mechanical digestion (mastication or chewing) Food breaks into pieces mixes with saliva so it forms a bolus Chemical digestion amylase (ptyalin) begins starch digestion at pH of 6.5 or 7.0 found in mouth when bolus & enzyme hit the pH 2.5 gastric juices hydrolysis ceases lingual lipase secreted by glands in tongue begins breakdown of triglycerides into fatty acids and glycerol
  • Slide 3
  • Motility of the mouth Food intake (voluntary, CN VII ) Mastication : (involuntary but highly affected voluntarily ) successive stretch & inverse stretch reflexes buccal swallowing (voluntary)
  • Slide 4
  • Mastication reflex Masticator Muscle Extrafusal fibers Muscle spindle Intrafusal fibers GTA Golgi-tendon apparatus + _ I.S.R S.R Mandibular branch Of CN V Trigeminal nuclei 2 Successive Stretch & Inverse stretch Reflexes fallow One another Sensory receptors Are muscle spindle & Golgi- Tendon Apparatus respectively Sensory & motor Neurons and integrating center Is of Mandibular branch Of Trigeminal nerve
  • Slide 5
  • Food Propulsion Swallowing (Deglutition) Buccal phase Food enters pharynx Pharyngeal phase Food passes through pharynx & enters esophagus esophagus esophageal phase Food passes through esophagus & enters the stomach Coordination of numerous actions by CN V, vii,IX,X, XI & XII
  • Slide 6
  • voluntary, tongue pushes food to back of oral cavity against the soft palate Once food contacts touch receptors in the pharynx & Pharyngeal Tonsils next phase starts Deglutition: Buccal phase
  • Slide 7
  • Deglutition: Pharyngeal phase Involuntary phase 1-Tongue lift against hard palate to close the mouth 2-soft palate & uvula are lifted to close off nasopharynx 3-breathing stops & airways are closed because: a-vocal cords close a-vocal cords close b-epiglottis is bent over airway as larynx is lifted b-epiglottis is bent over airway as larynx is lifted 4-Upper esophageal sphincter relaxes Epiglottis closes Upper esophageal Sphincter relaxes 5-Pharyngeal folds pulled away to form swallowing groove on the pharyngeal roof 6-A peristaltic wave passes the bolus to the esophagus
  • Slide 8
  • Deglutition: Esophageal phase Upper esophageal sphincter closes again Peristalsis pushes food down by contraction of circular fibers behind bolus down by contraction of circular fibers behind bolus longitudinal fibers in front of bolus shorten the distance of travel longitudinal fibers in front of bolus shorten the distance of travel Travel time is 4-8 seconds for solids and 1 sec for liquids Lower sphincter relaxes as food approaches Secondary peristaltic
  • Slide 9
  • Pressure changes in pharynx,esophagus & esophageal sphincters during swallowing
  • Slide 10
  • Control of lower esophageal sphincter LES is controlled by : Parasympathetic preganglionic fibers via ENS stimulatory & inhibitory neurons sympathetic which inhibit ENS neurons and directly stimulate LES L.E.S. MUSCLE NANC neuron VIP,ATP,NO - + - Vagal nucleus + Cholinergic Vagal neurons ENS Cholinergic Neuron Post ganglionic Sympathetic Neurons + - +
  • Slide 11
  • Gastroesophageal sphincter Diseases-1:Achalasea Lower sphincter fails to open distension of esophagus feels like chest pain or heart attack- Treatment Air balloon Surgical Myotomy sympathectomy
  • Slide 12
  • Gastro esophageal sphincter Diseases- 2 : (GERD) Lower esophageal sphincter fails to close stomach acids, bile & enzymes enter esophagus & erode esophagus Presentation: post- prandial heart burn, regurgitation at 1 hour Control the symptoms by avoiding a large meal and lay down in front of TV smoking and alcohol, coffee, chocolate, tomatoes, fatty foods, onions & mint Bending to tie the shoes Control the symptoms by taking Tagamet HB 60 minutes before eating neutralize existing stomach acids with Digel