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LIVER, GALL BLADDER

LIVER

     Where the stomach meets the small intestine in tunicates, there are a number of tubules collectively called the pyloric gland which empty through a duct into the intestine.  The cells resemble vertebrate liver cells (especially those of the most primitive fish, the hagfish) and function in the storage of glycogen and the removal of foreign substances from the blood, as in vertebrate livers (Burighel, from Harrison, 1997, p. 257). In all chordates, the veins which reach this structure from the intestines are portal veins (Stach, 2000).  In lancelets, the brownish-green hepatic sacculations (also called the hepatic cecum) are the primary source of digestive enzymes, releasing protease, amylase, and lipase.  (Ruppert, from Harrison, 1997, p. 444-5).  Amphioxus possesses a hepatic portal system in which blood from intestines brought to a capillary network in liver before the hepatic vein returns it to general circulation.  The same pattern of circulation exists in vertebrates (Willey, 54).

AMPHIOXUS

LANCELET
LANCELET
     In hagfish, the liver no longer functions in enzyme production and food absorption as in Amphioxus (Romer, p. 390).  Gnathostome livers increase in size and are lobed  (Weichert, 1970, p. 194).

HAGFISH

HAGFISH

HAGFISH

HAGFISH

LAMPREY

LAMPREY

LAMPREY

SHARK

SHARK

SHARK

GAR

GAR

GAR

BOWFIN

BOWFIN

PERCH

PERCH

LUNGFISH

LUNGFISH

FROG

FROG

SALAMANDER

SALAMANDER

TURTLE

TURTLE

OPOSSUM

OPOSSUM

 

CAT

CAT

CAT

SHEEP

SHEEP

PIG

PIG LIVER

MONKEY

MONKEY

HUMAN MODEL

HUMAN MODEL

GALL BLADDER

     In most vertebrates, the bile produced in the liver can be concentrated and stored in the gall bladder.  The cystic duct from the gall bladder and the hepatic duct from the liver fuse to empty into the common bile duct which, in turn, empties into the small intestine.  Jawless fish possess both a liver and gall bladder although the liver is small.  Lamprey gall bladders and bile ducts degenerate in adults (Weichert, 1970, p. 194).  A few species of shark, many birds, and a number of mammals (some artiodactyls, rodents, whales, seals, and perissodactyls) lack gall bladders  (Weichert, 1970, p. 194).  Although pigeons lack a gall bladder, it can be present during embryonic development (Weichert, 1970, p. 194).

HAGFISH

HAGFISH

HAGFISH

LAMPREY

LAMPREY

SHARK

SHARK

BOWFIN

BOWFIN

PERCH

PERCH

LUNGFISH

LUNGFISH

FROG

FROG

FROG
SALAMANDERSALAMANDER

ALLIGATOR

ALLIGATOR

CHICKENCHICKEN

OPOSSUM

OPOSSUM

 

SHEEP

SHEEP

GOAT

GOAT

PIG

GALLBLADDER

CAT

CAT

CAT

MONKEY

MONKEY

MONKEY

HUMAN MODEL

HUMAN MODEL