Physiological functions of the mouth ,pharynx & oesophagus 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 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

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

Mastication reflex 2 Successive Golgi-tendon apparatus Stretch & Inverse stretch Reflexes fallow One another Masticator Muscle Extrafusal fibers Muscle spindle Intrafusal fibers GTA Golgi-tendon apparatus + _ I.S.R S.R Mandibular branch Of CN V Trigeminal nuclei Sensory receptors Are muscle spindle & Golgi-Tendon Apparatus respectively Sensory & motor Neurons and integrating center Is of Mandibular branch Of Trigeminal nerve

Food Propulsion Swallowing (Deglutition) Buccal phase Pharyngeal 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

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

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 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

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

Pressure changes in pharynx ,esophagus & esophageal sphincters during swallowing

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 Neuron Post ganglionic Sympathetic Neurons

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

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