physiology of the stomach

8/9/2019 Physiology of the Stomach

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Physiology of the StomachPhysiology of the Stomach

AUTHOR: DAVID WALKER

LAST MODIIED: MAR!H "#$ %&"'

!o(te(ts )sho*+

ig ",& - O.e/.ie* of the stomach i( the gast/oi(testi(al t/act

The stomach is a 012 sha3e4 o/ga( of the gast/oi(testi(al t/act$ 4i/ectly

i(fe/io/ to the 4ia3h/agm, I( the 5I t/act$ it co((ects the oeso3hag6s to

the 46o4e(6m,

Its 3ositio( a(4 si7e .a/ies co(ti(6o6sly$ *ith the 4ia3h/agm36shi(g it

i(fe/io/ly 46/i(g i(s3i/atio( a(4 36lli(g s63e/io/ly o( e83i/atio(, The

stomach is .e/y 4iste(si9le to e(a9le it to accommo4ate foo4$ *he/e the

4igestio( of sta/ch$ 3/otei(s a(4 t/iglyce/i4es 9egi(s,

I( this a/ticle *e *ill loo at the 3hysiological 3/ocesses that occ6/ i( the

stomach$ a(4 a(y cli(ical co//elatio(s,

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6(ctio(s of the Stomach

As a 5I o/ga($ the stomach f6lfills ma(y f6(ctio(s$ all associate4 *ith

the sto/age a(4 4igestio( of foo4:

Mi8es sali.a$ foo4 a(4 gast/ic ;6ice to fo/m

chyme,

Rese/.oi/ fo/ foo4 9efo/e /elease i(to the small

i(testi(e,

Sec/etes gast/ic ;6ice *hich ca( ill 9acte/ia$

3e3si( to 4igest 3/otei(s$ i(t/i(sic facto/ to a9so/9

.itami(


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ig "," - The laye/s of the stomach *all,

I( the m6cosa$ e3ithelial cells e8te(4 4o*( i(to the lami(a 3/o3/ia to

fo/m gast/ic gla(4s,

These gla(4s sec/ete ma(y im3o/ta(t s69sta(ces(see Gastric glands,

below).

U(4e/(eath the m6cosa lies the s69m6cosa$ m6sc6la/is e8te/(a$ a(4

the se/osa:

The s69m6cosa is com3ose4 of a/eola/

co((ecti.e tiss6e,

The m6sc6la/is e8te/(a has th/ee laye/s of

smooth m6scle> a( o6te/ lo(git64i(al laye/$ a

mi44le ci/c6la/ laye/ a(4 a( i((e/ o9li?6e laye/,

The se/osa co.e/i(g the stomach is com3ose4 of

sim3le s?6amo6s e3itheli6m a(4 a/eola/


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co((ecti.e tiss6e, It is f6se4 *ith the .isce/al

3e/ito(e6m *ith o.e/lays the stomach

At the lesse/ c6/.at6/e of the stomach$ the a 4o69le laye/ of 3e/ito(e6m

e8te(4s 63*a/4 to the li.e/ as the lesse/ ome(t6m, At the g/eate/

c6/.at6/e of the stomach$ a(othe/ 4o69le laye/ of 3e/ito(e6m co(ti(6es

4o*(*a/4 as the g/eate/ ome(t6m$ 4/a3i(g o.e/ the i(testi(es,

5ast/ic 5la(4s

ig ",% - The e8oc/i(e cells of a gast/ic gla(4,

The gast/ic gla(4s a/e$ 9y 4efi(itio($ e8oc/i(e gla(4s, They co(tai( fo6/

mai( cell ty3es$ each *ith a 4iffe/e(t sec/etio(:

M6co6s (ec cells sec/ete m6c6s, Pa/ietal cells 3/o46ce i(t/i(sic facto/ a(4 H!l,

!hief cells sec/ete 3e3si(oge( a(4 li3ase,

5 cells sec/ete gast/i(,


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5ast/i( is a/g6a9ly the most im3o/ta(t sec/etio($ i(fl6e(ci(g the ma;o/ity

of the f6(ctio(s of the stomach,

Its f6(ctio(s i(cl64e

Stim6late 3a/ietal cells to sec/ete H!l a(4 chief

cells to sec/ete 3e3si(oge(,

!o(t/acts lo*e/ oeso3hageal s3hi(cte/,

I(c/eases stomach motility,

Rela8es 3ylo/ic s3hi(cte/,

Digestio(O(e of the ma;o/ f6(ctio(s of the stomach is to 9egi( the 4igestio( of

foo4, O(ce the foo4 9ol6s /eaches the stomach$ 3e/istaltic *a.es

mace/ate the foo4$ mi8i(g it *ith gast/ic sec/etio(s to fo/m a sol6tio(

(o*( as chyme,

ig ", @ - The 3e/istaltic e;ectio( *a.es of the stomach

As 4igestio( 3/ocee4s$ mo/e .igo/o6s mi8i(g *a.es 9egi( i( the 9o4y of

the stomach$ *ith the *a.es i(te(sifyi(g i( the 3ylo/6s,


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The 3ylo/ic s3hi(cte/$ *hich is (o/mally close4$ allo*s a small .ol6me of

chyme to 3ass th/o6gh i(to the46o4e(6m,

Most of the chyme ho*e.e/ is fo/ce4 9ac i(to the stomach 9o4y fo/

f6/the/ mi8i(g, A f6/the/ 3e/istaltic *a.e fo/ces the chyme to*a/4s the

3ylo/ic s3hi(cte/,

E(7ymatic 4igestio( of 3/otei(s 9egi(s i( the stomach, The mai(

e(7yme i(.ol.e4 is 3e3si($ sec/ete4 9y chief cells, Pe3si( 9/eas

3e3ti4e 9o(4s 9et*ee( ami(o aci4s$ 9/eai(g 4o*( a 3/otei( chai( i(to

smalle/ 3e3ti4e f/agme(ts, Pe3si( is most effecti.e a( aci4ic

e(.i/o(me(t$ *hich the stomach 3/o.i4es, This e(7yme is sec/ete4 as

the i(acti.e 3e3si(oge( so as to 3/e.e(t the 4igestio( of 3/otei(s that

3/o46ce it,

O(ly a small amo6(t of 4igeste4 (6t/ie(ts a/e a9so/9e4 i( the stomach$

9eca6se its e3ithelial cells a/e /elati.ely im3e/mea9le, M6co6s cells

a9so/9 some *ate/$ io(s$ alcohol a(4 sho/t chai( fatty aci4s,

5ast/ic Aci4 Sec/etio( i( the StomachMai(tai(i(g a( aci4ic e(.i/o(me(t is c/6cial to the 3/o3e/ f6(ctio(i(g of

the stomach, 5ast/ic aci4 is sy(thesise4 a(4 sec/ete4 9y the 3a/ietal

cells of the stomach,

The 3a/ietal cells ha.e a 6(i?6e st/6ct6/e, !a(alic6li i(.agi(atio(s of

the cell *alllB a/e 3/ese(t o( the l6me(al s6/face of the cell, These

i(.agi(atio(s 3lay a /ole i( the sec/etio( of gast/ic aci4:

", I( the mitocho(4/ia of the 3a/ietal cell$ *ate/ is

s3lit i(to HC a(4 OH=


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%, OH= com9i(es *ith !O%to fo/m H!O@=$ *hich

lea.es the cell i( e8cha(ge fo/ a !l= io(,

@, The HC is 36m3e4 i(to the l6me( of the gast/ic

gla(4 9y 3/oto( 36m3s o( the ca(alic6li,

', !l= io(s 4iff6se i(to the gast/ic l6me( f/om the

3a/ietal cell, They com9i(e *ith HC to f/om H!l,

The sight$ smell a(4 taste of foo4 i(itiates /efle8es that

stim6late 3a/asym3athetic (e6/o(s to /elease

acetylcholi(e, Acetylcholi(e a(4 gast/i( stim6late 3a/ietal cells to sec/ete

mo/e H!l, They also ca6se the /elease of histami(e$ *hich acts

sy(e/gistically to e(ha(ce the effects of acetylcholi(e a(4 gast/i(,

ig ",' - Mecha(ism of gast/ic aci4 sec/etio( f/om the 3a/ietal cells,

!li(ical Rele.a(ce: Physiological Diso/4e/s of the

Stomach


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Stomach Ulce/s

ig ", - A 3e3tic 6lce/,

A( 6lce/ is a( e/osio( i( the m6cosal laye/ of the stomach ,The/e a/e

t*o ty3es of 6lce/ i(.ol.i(g the stomach:

5ast/ic 6lce/s a/e lesio(s of the stomach m6cosa,

Pe3tic 6lce/s a/e lesio(s of the m6cosa of the

3ylo/ic ca(al o/ 46o4e(6m,

Ulce/s a/e ofte( associate4 *ith the 9acte/i6m Helicobacter pylori,

I(4i.i46als *ith a( 6lce/ ge(e/ally ha.e a high .ol6me of gast/ic aci4

sec/etio($ *hich o.e/*helms the9ica/9o(ate 96ffe/ a(4 /e46ces the

3/otecti.e (at6/e of the m6co6s li(i(g, H, 3ylo/i e/o4es the m6co6s li(i(g

/es6lti(g i( i(flammatio($ /e(4e/i(g the m6cosa .6l(e/a9le to gast/ic

aci4 a(4 3e3si(, If a( 6lce/ e/o4es i(to the gast/ic a/te/ies$ it ca( ca6se

se.e/e 9lee4i(g

Achlo/hy4/iaAchlo/hy4/ia is a co(4itio( *he/e gast/ic aci4 3/o46ctio( is a9se(t, It has

.a/io6s ca6ses$ i(cl64i(g hy3othy/oi4ism$ H, 3ylo/i i(fectio($ a(4

a6toimm6(e 4iso/4e/s,


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As the stomach 3H is (o lo(ge/ lo*$ 3e3si( ca((ot *o/ o3timally, The

highe/ 3H also fails to 3/e.e(t 9acte/ial /e3licatio($ a(4 3athoge(

o.e/g/o*th is a commo( fi(4i(g,

physiology of the stomach

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