The purpose of this study is to describe the histological,
histochemical and ultrastructural features
of pancreas of the grass carp (Ctenopharyngodon
idella), one of the common herbivorous freshwater
fish of Egypt. The pancreas is divided into exocrine
and endocrine portions. Exocrine pancreatic tissues
consists of scattered serous acini, and is observed
in two forms: 1) disseminated in the spleen
tissue, in mesentery around intestine and intestinal
bulb, and 2) intrahepatically, around the branches
of the portal vein. Two alveolar cell types are present
in pancreatic acini; centroacinar cells and typical
pyramidal acinar cells. Pancreatic stellate cells
(PSC) are demonstrated in the perivascular and
the periacinar space of the pancreas. The pancreatic
acini gave positive reaction to PAS, Best's carmine,
and osmium tetraoxide, and negative to alcian
blue. The acini also show high lipase and alkaline
phosphatase activity, and moderate activity for
acid phosphatase. Scanning electron microscopy
show apical microvilli of the acinar cells, and
branched PSC extend their processes between the
pancreatic cells. Ultrastructure of pancreatic acini
reveals well-developed rER, membrane-bound
zymogen granules, and abundant lipid droplets.
The duct system is composed of intralobular duct,
interlobular pancreatic duct and main duct opened
in the intestinal bulb. The endocrine parts of the
pancreas are organized as lightly staining Langerhan’s
islets between exocrine acinar cells found in
the liver, in mesenteries around the intestinal bulb
and the intestine, and consisted of three cell types.
Alpha cells were the most dominant cells, and
were ovoid in shape. Beta cells were polyhedral in
shape, and they grouped in small clusters. Delta
cells were small fusiform, argyrophilic cells. In conclusion,
the present study revealed that the exocrine
portion of the pancreas of the grass carp had
two forms, disseminated and intrahepatic, with
characteristic cellular and histochemical components,
and an endocrine portion that consisted of
Alpha, Beta and Delta cells.