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Digestive Physiology

Digestive Physiology. By: M.H.Dashti . Lecture 3. Physiological functions of the mouth ,pharynx & oesophagus . Digestion in the Mouth. Mechanical digestion (mastication or chewing) Food breaks into pieces mixes with saliva so it forms a bolus Chemical digestion

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Digestive Physiology

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

  2. Digestion in the Mouth • Mechanical digestion (mastication or chewing) • Food breaks into pieces • mixes with saliva so it forms a bolus • Chemical digestion • α 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

  3. Motility of the mouth • Food intake (voluntary , CN VII ) • Mastication : (involuntary but highly affected voluntarily ) • successive stretch & inverse stretch reflexes • buccal swallowing (voluntary)

  4. Golgi-tendon apparatus _ I.S.R + GTA S.R Trigeminal nuclei Masticator Muscle Extrafusal fibers Mandibular branch Of CN V Muscle spindle Intrafusal fibers Mastication reflex 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

  5. Food Propulsion • Swallowing (Deglutition) • Buccal phase • Food enters pharynx • Pharyngeal phase • Food passes through pharynx & enters esophagus • esophageal phase • Food passes through esophagus & enters the stomach Coordination of numerous actions by CN V, vii ,IX ,X, XI & XII

  6. Deglutition: Buccal phase • 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

  7. Epiglottis closes Upper esophageal Sphincter relaxes 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 b-epiglottis is bent over airway as larynx is lifted 4-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

  8. Deglutition: Esophageal phase • Upper esophageal sphincter closes again • Peristalsis pushes food down by contraction of circular fibers behind bolus 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

  9. Pressure changes in pharynx ,esophagus & esophageal sphincters during swallowing

  10. Vagal nucleus Post ganglionic Sympathetic Neurons Cholinergic Vagal neurons - + + - ENS Cholinergic Neuron + + - L.E.S. MUSCLE NANC neuron VIP,ATP,NO 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

  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

  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

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