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EXTENSIONS OF THE SEROSA

      In vertebrates, extensions of the serosa layer of the GI tract help to support the digestive organs.  In humans, these consist of the greater omentum, lesser omentum, falciform ligament, mesentery, and mesocolon.  In some primitive coelomates (Phoronida), mesenteries support the intestine.  (Hickman, p. 288).  In hagfish extensions of the peritoneum exist which surround and support the organs of the abdominopelvic cavity (Romer, p. 318-9).  By the appearance of gnathostome fish, these extensions of the peritoneum are identifiable as the greater and lesser omenta (from the greater and lesser curvatures of the stomach), the falciform ligament (attaching the liver dorsally), the mesentery (to small intestine), and the mesocolon (to the large intestine).  As the small intestine became more coiled in tetrapods, so did the mesentery  (Romer, p. 318-9).  In higher tetrapods, the greater omentum may store adipose.

HAGFISH

HAGFISH MESENTERY

MESENTERY
HAGFISH

LAMPREY

LAMPREY

SHARK

SHARK

EXTENSIONS OF THE SEROSA
EXTENSIONS OF THE SEROSA EXTENSIONS OF THE SEROSA
EXTENSIONS OF THE SEROSA

GAR

GAR

GAR
GAR GAR
BOWFINBOWFIN

PERCH

PERCH

PERCH

SALAMANDER

SALAMANDER

FROG

FROG

FROG
FROG

TURTLE

TURTLE

TURTLE

ALLIGATOR

ALLIGATOR