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igestionSystem
iktiol - ch 4 - tamu 68IV2013 1
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What is digestion?
• the breakdown of large insolublemolecules into smaller soluble moleculeswhich can pass through the wall of the
gut into the blood.
• mechanical & chemical breakdown offood into nutrients.
• chemical reactions breaking down foodand releasing energy from nutrients.
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iktiol - ch 4 - tamu 68IV2013 3
• Ingestion
• Processing
• Absorption• Elimination
Digestion System
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• Primitive chordates wereflter eeders.
• Jaw development allowedmore aggressive methods oeeding
• However some o the largestmammals retain fltereeding !baleen whales".
ngestion
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• Proc#rement and manip#lationo ood$ sensory.
• present in shar%s bony fsh and
amphibians• cannot move independently
• An e&tension o the gland#larfeld o the pharyngeal 'oor is#sed by terrestrial amphibiansto capt#re prey
ong#e !Primary (ong#e"
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Primary (ong#e) mesenchyme ohyoid arch
• present in shar%s bony fsh and
amphibians
• cannot move independently
• An e&tension o the gland#larfeld o the pharyngeal 'oor is#sed by terrestrial amphibiansto capt#re prey
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comparison
Digestion System
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Vertebrate Digestive Tube
Myxini &lampreys
Chondrichthys Non-TeleostActinopterygii
oral cavity oral cavity oral cavity oral cavity
pharynx gill openings gill openings gill openings
esophagus short short short
stomach absent present present
intestine simple with
spiral valve
simple with
spiral valve
simple with
spiral valve
cloaca present present absent
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Teleosts Lungfishes Amphibians
oral cavity oral cavity oral cavity oral cavity
pharynx gill openings gill openings gill openingswhen larval
esophagus short short long
stomach present absent present
intestine simple, NO spiral valve simple withspiral valve
NO spiral valve,small intestine
large intestine
cloaca absent present present
Vertebrate Digestive Tube
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internal organs
Digestion System
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• Brain: seat of the mental faculties of a fish.
• so!ha"us: !art of the #i"esti$e tract connectin" the mouth to the
stomach.
• %orsal aorta: $essel in the &ack that carries &loo# from the heart to
the or"ans.
• 'tomach: !art of the #i"esti$e tract &et(een the eso!ha"us an# the
intestine.
• )ir &la##er : !ocket in (hich urine collects.
• '!inal cor#: !art of the ner$ous s*stem that connects the &rain to
all other !arts of a fish.
• +i#ne*: &loo#-!urif*in" or"an.• ,rinar* orifice: o!enin" for eliminatin" urine.
• enital rifice: o!enin" relate# to the "enital or"ans.
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• )nus: en# of the #i"esti$e tract.
• ona#: hormone-secretin" se/ual "lan# of a fish.
• Intestine: last !art of the #i"esti$e tract.
• *loric cecum: cul-#e-sac relate# to the intestine.
• all &la##er : small sac containin" the &ile.
•i$er : &ile-!ro#ucin" #i"esti$e "lan#.
• eart: &loo#-!um!in" or"an.
• ills: res!irator* or"an of a fish.
• ooth: har# or"an of a fish use# to shre# foo#.
• *e: si"ht or"an of a fish.• lfactor* &ul&: &ul"in" !art of the smell or"an of smell of a fish.
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nares or e/ternal nostrils locate# on the un#ersi#e
$entral surface of the rostrum anterior to the a(s.
) nasal fla! se!arates the incurrent from the
e/current o!enin". ater !asses into an# out of the
olfactor* sac !ermittin" the shark to #etect the
o#ors of the (ater.
he !atches of !ores on the hea# in the areas of the
e*es snout an# nostrils are the o!enin"s of the
am!ullae of oren9ini. hese sense or"ans aresensiti$e to chan"es in tem!erature (ater !ressure
electrical fiel#s an# salinit*.
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Internal anatom* of a shark:
lar"e lon" an# $er* !o(erful selachian fish. It is $i$i!arous.
• arietal muscles: set of muscles of the si#e of the hea#.
• Verte&ra: each of the &ones formin" the s!inal column.
• eural arch: arche# !art of a $erte&ra relate# to the ner$ous
s*stem.
• Bo#*: main !art of a $erte&ra.• %orsal fin: locomoti$e lim& on the &ack of a shark.
• )nterior intestine: !art of the #i"esti$e tract ust after the stomach.
• 'tomach: !art of the #i"esti$e tract of a shark &et(een the front
an# rear !arts of the intestine.• +i#ne*: &loo#-!urif*in" or"an.
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Internal anatom* of a shark
• '!inal cor#: !art of the ner$ous s*stem containe# in the s!inal
column.
•
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Internal anatom* of a shark
• eart: &loo#-!um!in" or"an.• Ventral aorta: &loo# $essel in the aomen that carries &loo# from
the heart to other or"ans.
• Inner s!iracle o!enin"s: fissure containin" the $iscera.
• =outh: entrance to the #i"esti$e tract.• har*n/: intersection of the res!irator* an# #i"esti$e tracts of a
shark.
• nce!halon: seat of the mental ca!acities of a shark.
• 'kull: &on* case of the &rain.
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li$er
s!iral $al$e intestine
stomach
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Chemistry of DigestionHydrolysis digests foods:
• Carbohydrates (starches) - become simplesugars
• Proteins - become amino acids
• Fats - become fatty acids & glycerol• Nucleic acids (RN! "N) - become
nucleotides
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Carbohydrate Digestion
• #egins in mouth - sali$ary amylase brea%s donstarch
• 'talled in the stomach
• ostly occurs in small intestine aided byfolloing enymes:
a* Pancreatic enymes - brea%s starch into
maltoseb* altase - brea%s maltose into + glucoses
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Carbohydrate Digestion
c* 'ucrase - brea%s sucrose into , glucose and ,fructose
d* actase - brea%s lactose into , glucose . ,
galactose
• ast / enymes produced by small intestine*
Folloing absorbtion! glucose! fructose! &
galactose transported to the li$er here they arecon$erted to glycogen*
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Fat Digestion
0astric lipase of stomach brea%s don some fats*
ost fat digestion occurs in small intestine*bile emulsifies fat! e1posing more fat to enymes*
#ile salts lin% fat molecules to ater molecules2 (normally
fats are hydrophobic)*
Pancreatic lipases continues fat digestionsubunits no cross into micro$illisubunits are reassembled into triglycerides! combined ith
cholesterol! and transported to the circulatory system*
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Protein Digestion
• 'tomach - pepsinogen con$erted to pepsin in thepresence of HC* Pepsin brea%s some of the
peptide bonds of some proteins*
• 'mall intestine - Pancreatic enymes trypsin &
chymotrypsin brea% proteins into smaller and
smaller units* 3he pancreatic enyme
carbo1ypeptidase brea%s peptides into free aminoacids* 'e$eral enymes produced by the small
intestine further brea% peptides into amino acids*
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mino acids- absorbed and transported to the li$er*
use# #irectl* &* the li$er to make li$er !roteins others con$erte# to acet*l coen9*me ) use# in citric
aci# c*cle
other amino aci#s sent to $arious !arts of the &o#* for
!rotein s*nthesis.
Proteases must be acti$ated before being usedre$ents them from &reakin" #o(n !ancreas (here the*>re
ma#e ? store#.)cti$ation occurs (hen the* come in contact (@ certain
chemicals foun# in the small intestine.
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Nucleic Acid Digestion
4nymes called nucleases brea% don nucleic acids
such as RN (ribonucleic acid) and "N
(deo1yribonucleic acid) into nucleotide chains*
3he pancreas produces ribonuclease and
deo1yribonuclease
small intestine produces nucleases that brea% don
nucleotides into smaller subunits*