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Digestive PhysiologyDigestive Physiology
Physiological functions of Physiological functions of
the mouth ,pharynx & the mouth ,pharynx & oesophagus oesophagus
By: M.H.Dashti
Lecture 3
Digestion in the MouthDigestion in the Mouth Mechanical digestion (mastication or chewing)Mechanical digestion (mastication or chewing)
Food breaks into piecesFood breaks into piecesmixes with saliva so it forms a bolus mixes with saliva so it forms a bolus
Chemical digestionChemical digestion– αα amylase (ptyalin) amylase (ptyalin)
begins starch digestion at pH of 6.5 or 7.0 found begins starch digestion at pH of 6.5 or 7.0 found in mouthin mouth
when bolus & enzyme hit the pH 2.5 gastric when bolus & enzyme hit the pH 2.5 gastric juices hydrolysis ceasesjuices hydrolysis ceases
– lingual lipaselingual lipasesecreted by glands in tonguesecreted by glands in tonguebegins breakdown of triglycerides into fatty begins breakdown of triglycerides into fatty
acids and glycerolacids and glycerol
Motility of the mouthMotility of the mouth
Food intake (voluntary , Food intake (voluntary , CN VII )CN VII )
Mastication : Mastication : (involuntary but highly (involuntary but highly affected voluntarily )affected voluntarily )– successive stretch & successive stretch &
inverse stretch reflexesinverse stretch reflexes buccal swallowing buccal swallowing
(voluntary)(voluntary)
Mastication reflexMastication reflex
MasticatorMuscle
Extrafusalfibers
Muscle spindleIntrafusal fibers
GTA
Golgi-tendon apparatus
+_
I.S.R
S.R
Mandibular branchOf CN V
Trigeminalnuclei
2 SuccessiveStretch&
Inverse stretch Reflexes fallowOne another
Sensory receptorsAre muscle spindle
&Golgi-Tendon Apparatus respectively
Sensory & motor Neurons and integrating center Is of Mandibular branchOf Trigeminal nerve
Food PropulsionFood Propulsion
Swallowing (Deglutition)Swallowing (Deglutition)– Buccal phaseBuccal phase
Food enters pharynxFood enters pharynx
– Pharyngeal phasePharyngeal phaseFood passes through pharynx & Food passes through pharynx &
enters enters
esophagus esophagus
– esophageal phaseesophageal phaseFood passes through esophagus & Food passes through esophagus &
enters the stomach enters the stomach
Coordination of numerous actions by CN V, vii ,IX ,X, XI & XII
voluntary, tongue voluntary, tongue pushes food to back pushes food to back of oral cavity of oral cavity against the soft against the soft palatepalate
Once food contacts Once food contacts touch receptors in touch receptors in the pharynx & the pharynx & Pharyngeal Tonsils Pharyngeal Tonsils next phase startsnext phase starts
Deglutition: Deglutition: BuccalBuccal phase phase
Deglutition: Pharyngeal phaseDeglutition: Pharyngeal phase Involuntary Involuntary
phasephase1-Tongue lift against 1-Tongue lift against
hard palate to close hard palate to close the mouththe mouth
2-soft palate & uvula 2-soft palate & uvula are lifted to close off are lifted to close off nasopharynxnasopharynx
3-breathing stops & 3-breathing stops & airways are closed airways are closed because:because:
a-vocal cords closea-vocal cords close b-epiglottis is bent b-epiglottis is bent
over airway as over airway as larynx is liftedlarynx is lifted
4-Upper esophageal 4-Upper esophageal sphincter relaxessphincter relaxes
Epiglottis
closes
Upper esophagealSphincter 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 phaseDeglutition: Esophageal phase Upper esophageal Upper esophageal
sphincter closes againsphincter closes again Peristalsis pushes food Peristalsis pushes food down by contraction of down by contraction of
circular fibers behind circular fibers behind bolusbolus
longitudinal fibers in longitudinal fibers in front of bolus shorten front of bolus shorten the distance of travelthe distance of travel
Travel time is 4-8 Travel time is 4-8 seconds for solids and seconds for solids and 1 sec for liquids1 sec for liquids
Lower sphincter relaxes Lower sphincter relaxes as food approachesas food approaches
Secondary peristalticSecondary peristaltic
Pressure changes in Pressure changes in pharynx ,esophagus & esophageal pharynx ,esophagus & esophageal
sphincters during swallowingsphincters during swallowing
Control of lower esophageal sphincterControl of lower esophageal sphincter LES is controlled LES is controlled
by :by :– Parasympathetic Parasympathetic
preganglionic preganglionic fibers via ENS fibers via ENS stimulatory & stimulatory & inhibitory inhibitory neurons neurons
– sympathetic sympathetic which inhibit ENS which inhibit ENS neurons and neurons and directly stimulate directly stimulate LESLES
L.E.S. MUSCLE NANC neuron VIP,ATP,NO
-
- +
Vagalnucleus
+
Cholinergic Vagal neurons
ENS Cholinergic
Neuron
Post ganglionicSympathetic Neurons
+ -
+
Gastroesophageal sphincter Gastroesophageal sphincter Diseases-1:AchalaseaDiseases-1:Achalasea
Lower sphincter fails to openLower sphincter fails to open– distension of esophagus feels like chest distension of esophagus feels like chest
pain or heart attack-pain or heart attack- TreatmentTreatment
– Air balloon Air balloon – SurgicalSurgical
MyotomyMyotomysympathectomy sympathectomy
Gastro esophageal sphincter Diseases- Gastro esophageal sphincter Diseases- 2 : (GERD)2 : (GERD)
Lower esophageal sphincter fails to closeLower esophageal sphincter fails to close– stomach acids , bile & enzymes enter esophagus & erode esophagusstomach acids , bile & enzymes enter esophagus & erode esophagus
Presentation: Presentation: post- prandial heart burn, post- prandial heart burn, regurgitation at 1 hourregurgitation at 1 hour– Control the symptoms by avoidingControl the symptoms by avoiding– a large meal and lay down in front of TVa large meal and lay down in front of TV– smoking and alcohol , coffee, chocolate, tomatoes, fatty foods, onions smoking and alcohol , coffee, chocolate, tomatoes, fatty foods, onions
& mint& mint– Bending to tie the shoesBending to tie the shoes
Control the symptoms byControl the symptoms by – taking Tagamet HB 60 minutes before eatingtaking Tagamet HB 60 minutes before eating– neutralize existing stomach acids with Digel neutralize existing stomach acids with Digel