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Chapter 3
DIGESTION &
ABSORPTION
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Digestion
• Digestion – The process of changing foodinto simpe components !hich the "od#can a"sor"
• Digesti$e tract or Gastrointestina tract%!here digestion & a"sorption tae pace
• 'o(th%)esophag(s%)stomach%)smaintestine%)arge intestine
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GI Tract Anatom#
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Digestion
• 'o(th – ingestion of food* che!ing+mastication, & s!ao!ing
-. Bo(s – portion of food s!ao!ed
at one time/. Sai$a % !ater0 sats0 en1#mes0
m(c(s secreted "# sai$ar# gands
to2 a. 'oisten food & aids s!ao!ing
". Begins car"oh#drate digestion
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Digestion
• Esophag(s – connects mo(th to stomach
-. Epigottis – coses air!a#
/. Bo(s mo$ed aong "# peristasis
3. 4ardiac sphincter – eeps food from"acing (p into esophag(s
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Digestion
• Stomach – coecting & ch(rning-. Gastric gands secrete2 gastric 5(ice
+!ater0 en1#mes0 h#drochoric acid, that
is most "acteria and "egins proteindigestion and m(c(s to protect ining
/. 4h#me – semi%i6(id mass of partia#
digested food3. P#oric sphincter – reg(ates passage
of ch#me into sma intestine
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Secretions of Digestion
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Digestion
•Sma Intestine – 3 segments2-. D(oden(m – opening from common "ie d(ct
secretes f(ids from2
a. 7i$er & Ga"adder – "ie em(sifies fat
". Pancreas – am#ase "rea do!n car"oh#drate0 sodi(m "icar"onate
ne(trai1es the acidic ch#me and ipase
/. 8e5(n(m
3. Ie(ma. Ieoceca $a$e – sphincter that reg(ates
passage of ch#me into arge intestine
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Digestion
• 7arge intestine +coon, % rea"sor"ing & eiminating
-. 9ermentation of (ndigested
resid(es "# "acteria occ(rs/. Terminates at rect(m0 !here !ater
some mineras are a"sor"ed
3. An(s – sphincter that contros defecation +e:cretion of fi"er
resid(e0 !astes and some !ater,
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The 9ina Stage
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Digestion
• '(sc(ar action heps to prope i6(efied
food thro(gh the G.I. tract "#2
-. Peristasis – m(sc(ar contractions
that p(sh contents for!ard
/. Segmentation – in!ard s6(ee1ing for
greater mi:ing of secretions3. Sphincter contractions
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Peristasis
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Segmentation
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Sphincter 4ontractions
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A"sorption & Transport
• End%prod(cts of digestion2
-. 4;O ))) 'onosaccharides
/. 9ats ))) G#cero < fatt# acids3. Proteins ))) Amino acids
=. >itamins0 mineras & !ater – no
digestion
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A"sorption
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A"sorption & Transport
• A"sorption occ(rs in the sma intestine
-. ?a of sma intestine co$ered
!ith -@@s of fods/. Each fod co$ered !ith -@@@s of
$ii
3. Each $ii contains -@@s of micro$ii
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The Sma Intestine >ia
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A"sorption & Transport
• A"sor"ed n(trients enter either the2
-. >asc(ar s#stem – !ater%so("e
n(trients +monosaccharides0 amino
acids0 !ater%so("e $itamins0
mineras0 !ater, enter the "ood $ia
the porta $ein for transport to thei$er
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A"sorption & Transport
/. 7#mph s#stem – fat%so("e n(trients
+ipids0 fat%so("e $itamins, enter here0
e$ent(a# entering the "ood near the
heart
3. Transport of ipids – since fats are inso("e in
!ater0 the# m(st "e pacaged for transport as
ipoproteins +trig#ceride0 phosphoipid0 protein0
choestero,
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A"sorption & Transport= "asic t#pes of ipoprotein2
-. 4h#omicrons – $er#0 $er# o! densit#
+C trig#ceride,* a"sor"ed from sma
intestine into #mph & circ(ated to ces
!here some of ipid materia is piced off
& remnants ret(rn to i$er
/. >7D7 – $er# o! densit# ipoprotein +@C trig#ceride,* made "# i$er &
tra$es to ces
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A"sorption & Transport
3. 7D7 – o! densit# ipoprotein +@C
choestero,* remains of >7D7* high
e$es increase ris of heart attac
=. ;D7 – high densit# ipoprotein +@C
protein,* remo$es choestero from "ood
for ret(rn to i$er* high e$es decrease
ris of heart attac
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pper GI Pro"ems
Dysphagia – diffic(t# s!ao!ing !ithtendenc# to choeaspirate
-. 9oods that are soft te:t(re & smooth
consistenc# critica to a$oid aspiration+i.e. p(dding consistenc# or p(reed,
/. Thicened i6(ids (sing commercia
thiceners are easier to s!ao!
3. T("e feeding into d(oden(m ma# "eindicated
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pper GI Pro"emsReflux esophagitis +Fheart"(rn, !hich often occ(rs d(e
to a hiata hernia and
Gastritis (infammation of stomach ining, and
Peptic Ulcers +erosions of the ining of stomach or
d(oden(m, re6(ire a bland diet to red(ce
gastric secretions and eiminate foods that
ca(se pain or discomfort
-. A$oid chocoate0 gariconions0 caffeine0
spic# & fatt# foods0 mint0 acoho
/. Sma meas !ith f(ids "et!een meas
3. Antacids & acid controers
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Gastroesophagea Ref(:
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Digesti$e Pro"ems
Delayed Gastric Emptying – ma# "e dea#ed
temporari# foo!ing s(rger# or chronica#
d(e to Dia"etes 'eit(s
-. 7o! fi"er0 o! fat speeds gastric empt#ing
& pre$ents "e1oars that ma# form a
"ocage
Constipation – pre$ent !ith a high fi"er diet and
treat "# drining pent# of f(ids inc(ding pr(ne 5(ice0 get reg(ar e:ercise & add a:ati$es
+h#drophiic cooids,0 as needed
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Digesti$e Pro"ems
Diarrhea/dehydration – treat (nder#ingca(se and repace f(ids & eectro#tes topre$ent deh#dration
-. 'id cases (se 5(ices0 sports drins0
caffeine%free sodas0 tea0 "roth0 orareh#dration form(as +e.g. Pedia#te,
Dierticular Disease
-. A$oid n(ts0 seeds0 h(s +e.g. ora0stra!"erries0 popcorn, !hich ma#
get trapped & ca(se di$ertic(itis
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Di$ertic(a in the 4oon
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'aa"sorption S#ndromes
Dumping !yndrome
4ar"oh#drate maa"sorption that occ(rs d(e to
remo$a of p#oric sphincter from partia
gastrectom# ca(sing osmotic diarrhea
-. S#mptoms inc(de !eaness0 di11iness0rapid heart"eat0 diarrhea0 a"domina pain
/. A$oid concentrated s!eets0 drin f(ids
"et!een meas0 eat sma0 fre6(ent meas
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'aa"sorption S#ndromes
"actose #ntolerance
4ar"oh#drate maa"sorption d(e to a ac of
the en1#me actase that spits actose into
g(cose < gaactose
-. Incidence assoc. !ith aging0 certain ethnicgro(ps0 and G.I. disease or s(rger#
/. S#mptoms inc(de cramping0 distention0
diarrhea after cons(ming prod(cts containing
mi or actose3. 7actose%Restricted Diet or en1#me ta"ets &
treated mi are aso a$aia"e
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'aa"sorption S#ndromes
$at %alabsorption – ca(sed "# disorders of thestomach0 intestine0 pancreas & i$er
-. Steatorrhea +fatt#0 oose0 foam#0 fo(
smeing stoos, !ith s("se6(ent oss of
energ#0 essentia fatt# acids0 and fat%so("e
$itamins
/. 7imit fat intae to 3%=@ gmsda#
3. S(ppementation !ith fat%so("e $itamins+!ater%misci"e forms a$aia"e,
=. En1#me repacement to aid digestion
& a"sorption
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'aa"sorption S#ndromes
Pancreatitis – infammation of the pancreas0
res(ting in impaired digestiona"sorption-. S#mptoms inc(de se$ere a"domina pain0
and na(sea & $omiting
/. Initia#0 N.P.O. +nothing "# mo(th, to rest
the pancreas (sing I.>. f(ids to maintain
f(id & eectro#te "aance
3. A$oiding acoho is imperati$e as diet
progresses=. 4hronic pancreatitis ma# ead madigestion
of fats0 chronic a"domina pain0 !eight oss
& dia"etes
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'aa"sorption S#ndromes
Cystic $ibrosis – hereditar# diseasecharacteri1ed "# thic m(c(s affecting man#"od# organs0 inc(ding (ngs & pancreas0 anda"norma# high eectro#te concentration in
s!eat-. Energ# & n(trient needs -/@%-@C of norma
/. 9at needed to meet high energ# needs so
en1#me repacements (sed to controsteatorrhea
3. 7i"era (se of f(ids & sat
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'aa"sorption S#ndromes
Celiac Disease +G(ten%sensiti$e enteropath#, –sensiti$it# to giadin0 part of the protein g(ten0fo(nd in !heat0 r#e0 "are# & oats
-. S#mptoms inc(de !eight oss0 diarrhea0
fatig(e0 anemia +iron0 foate0 >it. B-/,0
generai1ed maa"sorption0 "one disease
/. A$oiding foods containing g(ten re6(ires
reading a"esH