git phsyiology part i by dr akgupta (1)

8/10/2019 Git Phsyiology Part i by Dr Akgupta (1)

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Mastication (Chewing)Chewing is the first mechanical process in the GI tract in whichfood is broken down into small particles and a soft bolus is formed.

Importance of Chewing3. Food is broken into small particles required for enzyme

actions.4. i!ing with sali"a so that bolus can be swallowed

easily#. Grinding the food to a "ery fine particles pre"ents

in$ury to the GI%

Muscles of Mastication &'. asseter (. %emporal 3. )terygoids 4. *uccinator.

Movements associated with Mastication &

''.+pening , closure of mouth


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Control +f mastication

.1. The centre for mastication is located in medulla & cerebralcortex.

. The muscles of mastication are suplied b! mandibular division of

" cranial nerve .

/ cranial0er"e1


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2welling can be di"ided into

(1+ral 2tage & a voluntary stage in whichfood enetrs pharyn! frommouth.31)haryngeal stage5 an in"oluntary stage

in which food is enters esopahgus fromthe pharyn!.416sophageal stage5in"oluntary phase in

which food enters stomach from theesophagus.


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' . #ral $tage of

'. /oluntary 2tage in which after the Food isrolled into a bolus by chewing followingactions occur&

(. %he bolus is placed on poster5odorsal part of

tongue3. %he anterior part of tongue is retracted ,depressed

4. %he posterior part of tongue is ele"ated andpressed against hard palate. %his pushes thebolus backward into pharyn!.


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(. har!ngeal $tage of $wallowingIt is an Involuntar! stageThe phar!nx is a common passage for food and air . It has two

e!its 9 one into esophagus for food the other into laryn! for air.

%he :aryn! lies anterior to esophagus opening. 6sophagusopening lies posterior to laryn! opening. Further pharyn! is alsoconnected to naso5pharyn! behind nose . 2o food in pharyn! cango to esopahagus or laryn! or nose or back to mouth.

It is ensured that the food enters onl! esophagus as under &

d. 'eturn of food bac into mouth is prevented by tonguebeing pressed against the palate creating high pressure in oralca"ity

e. ntr! of food into naso*pha!r!nx is prevented by ele"ationof soft palate , u"ula.

f. ntr! of food intol+ungs through lar!nx is prevented by; /ocal cords of two side come "ery near each< :aryn! mo"e forward , upward= 6piglottis co"er the laryn! opening glotiis.

'> %emporary arrest of breathing during this stage of deglutition


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d. ntr! of food into esophagus & 0ow the other 3passages as mentioned abo"e are closed so foodcan enter only esopahagus by following

mechanism&( 8hen laryn! mo"es upward it opens the esophagus

opening wider.3 %he upper 354 cm of esophagus called ?62 ?pper

6sophageal 2phincter1 rela!es4 Contraction of pharyngeal muscles forces food into

esopahgus.


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,. sophageal $tage of $wallowing. It is also in"oluntary.8hen bolus reaches the esophagus peristaltic mo"ementsstarts in esophagus to propel food down into stomach.

%wo types of peristaltic mo"ements& primary peristalsis andsecondary peristalsis .rimar! peristalsis is continuation of the peristaltic wa"e thatbegins in the pharyn! , passes all the way from the pharyn!to the stomach in about < to '> seconds.$econdar! eristalsis - It remo"e any retained food particlesfrom esophagus if primary peristalsis fails to remo"e them andsend to stomach. 'ole of + $ (+ower sophageal $phincter)

#. 8hen a peristaltic wa"e passes down the esophagus thereis @recepti"e rela!ation@ of the lower esophageal sphincterahead of the peristaltic wa"e which allows easy propulsionof the swallowed food into the stomach.

;. After entry of food into stomach :62 contracts to not allowreflu! of acid of stomach into esophagus. Bowe"er . If the


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eglutition -efle!Ist stage of deglutition is /oluntary while nd & , rd $tagesof %eglutitin are Involuntar! and through deglutition

reflex mechanism .$timulus & %he sensory receptors in oro5phayryn! speciallyarea in a ring around the phar!ngeal opening withgreatest sensitivit! on the tonsillar pillars getsstimuted when food reaches here./fferent 0ibres & impulses from pharyngeal receptors passthrough glasso5pharyngeal ner"e I cranial ner"e1 todeglutititon or swallowing centre in medulla see n!t slidefor photo1.

%eglutition Centre & it is located in floor of 4th

/entricle inedulla oblongata of brain.fferent 0ibres & Impulses from deglutition centre tra"elthrough glasso5pharyngeal ner"e I cranial ner"e1 , "agusner"e cranial ner"e1 , reach soft palate palate pharyn!, esophagus.


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A)):I6 )BD2I+:+GD

' . %!sphagia & it is difficulty in swallowing.

Causes&c. echanical obstruction in esophagus 9

tumor stricture di"erticula

d. ecresaed mo"ements of esophagus egin parkinsonism a neurological disorder.e. uscle dosrders with theresult dificult

swallowing during oral , esophgealstages.


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A)):I6 )BD2I+:+GD

(. /chalasia & 8hen :ower esophageal

sphincter fails to rela! during swallowingthe food accumulates in esophagus causingits distention and symptoms as under&b. ysphagiac. Chest paind. 8eight loss

e. Cough


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A)):I6 )BD2I+:+GD

3. 2 '% (gastro esophageal refluxdisease)ue to weakness or failure of :ower6sophageal 2phincter to constrict causing

reflu! of acid contents of stomach intolower end of esophagus causing reflu!esophagitis with symptoms&

c. Beart burnd. 6sophagitise. ysphagia


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+/6 60%2 +F 2%+ ACB

1. 3452 ' C#5T'/CTI#5$

. ' C TI" ' +/ /TI#5,. eristalsis of $tomach- 0I++I52 &M T6I52

1. 3452 ' C#5T'/CTI#5$-8hen the person is empty stomach hungercontractions occurs. %hey are peristaltic wa"es

superimposed upon normal smooth musclecontractions.%he peristaltic wa"es of normal stomach whenfood is there occur in body , pyloric part of


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T!pe of 3452 ' C#5T'/CTI#5$

T!pe I &

%hey are the first contractions in empty stomach when stomach tone islow.

%heir duration is (> seconds , occur e"ery 354 seconds.

they produce a pressure of 7 cm of water ,

2tomach tone is normal in between the contractions.T!pe II &

%hey appear when tone of stomach is stronger and if the food intake ispostpones e"en on start of %ype I Bunger Contractions.

%heir duration of each contraction is (> seconds like in type I but there is

no pause between the contractions so the)ressure produced in stomach is '>5'7 cm of water.

T!pe III &+ccur when food is not taken despite type II contractions

It is incomplete tetanus and tone of stomach muscle increases muchmore.


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A)):I6 )BD2I+:+GD

(. ' C TI" ' +/ /TI#5 #0$T#M/C3-'elaxation of upper part of stomachwhen bolus of food enters thestomach from esophagus is called' C TI" ' +/ /TI#5 It occurs infundus and upper part of bod! ofstomach to receive & accommodate

food without increase in pressure ofstomach so no discomfort to person.


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eristalsis of $tomach'. 8hen food enters stomach5smoothmuscle of stomach start contracting E3 min. %he contractions start in lower partof body of stomach , pas to the pyloricsphincter. %he contractions mo"e towards

pyloric sphincter and takes ' min to reachat pyloric sphincter from point of origin inbody of stomach. %hey are calleddigestive peristalsis because with tightpyloric end food is crushed by them instomach and grinded for better action of$uices , enzymes.

git phsyiology part i by dr akgupta (1)

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