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