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BLOOD VESSELS 3
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4)
BLOOD VESSELS TO THE GASTROINTESTINAL TRACT The
dorsal aorta sends out several unpaired arteries to the abdominal organs:
the celiac, anterior mesenteric, and posterior
mesenteric arteries. In higher
vertebrates, the hepatic, left gastric, and splenic
arteries originate from the celiac. Lampreys
have four arteries including the celiac artery although there is no mesentery
( Hardisty 250). Shark: |
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MONKEY |
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HEPATIC
PORTAL VEIN In Amphioxus,
there is a large subintestinal vein which transports
nutrients from the gut cranially. In Amphioxus,
the hepatic portal vein forms a plexus of vessels in the hepatic cecum which rejoin to form the hepatic vein and subsequently
the portion of the endostylar artery called
the sinus venosus. (Ruppert, from Harrison,
1997, p. 445-52; Willey 49,54). The hepatic portal system, which brings blood
directly from the GI tract to the liver, has been little modified since
the early chordates. In both lancelets
and hagfish, the hepatic portal vein is contractile (Guenther, 154). This subintestinal
vein in the early embryo is formed from the vitelline
veins of the yolk (Hardisty). In vertebrates with a large amount of yolk,
(and in mammals, because they evolved from reptilian ancestors with large
amounts of yolk), prominent vitelline veins
join the subintestinal vein. |
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SHARK |
GAR |
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LUNGFISH |
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OPOSSUM |
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CAT |
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