Morphological Studies On Livers And Pancreases Of Culter Alburnus, Mystus Macropterus And Siniperca Scherzeri

From September, 2005 to February, 2006, anatomic structures and microstructures of livers and pancreases and ultrastructures of livers of Culter alburnus, Mystus macropterus and Siniperca scherzeri were in detail observed by means of anatomy, histology and transmission electron microscopy. The results are as follows:The anatomic structures of livers and pancreases of the 3 fishes have their own characteristics.The liver of C. alburnus has 3 strips of leaf, namely left, right and ventral leaf. There is a central vein and a central bile duct inside every leaf of liver, and they accompany each other. The central veins of left and ventral leaf of liver are joined together into 1 vein which is called the left vein of liver after it goes out of the liver;after going out of the liver, the one of the right leaf of liver is called the right vein of liver;2 veins of liver go into the vein sinusoid. The central bile ducts of left and ventral leaf of liver are joined together into 1 bile duct which is called the left hepatic duct after it goes out of the liver;after going out of the liver, the one of the right leaf of liver is called the right hepatic duct;2 hepatic ducts each open into the cystic duct near the intestines. After left and right hepatic duct and the cystic duct are joined together, the relatively enlarged and short common bile duct that opens into the forepart of intestines near the esophagus is formed.The liver of M. macropterus has 2 leaves, namely left and right leaf and the left one is more developed than the right one. 2 leaves of liver each send out left and right vein of liver and the 2 veins go into the vein sinusoid. Left and right portal vein encounter before entering the liver, therefore a bow-shaped vein which sends out 8~10 small veins of going into the liver is formed. Every leaf of liver sends out 2~3 hepatic ducts which directly go into the gall bladder. The cystic duct opens into the forepart of intestines near the stomach.The liver of S. scherzeri has 3 leaves, namely left, medium and right leaf. Left, medium and right vein of liver are sent out from the medium leaf of liver and the 3 veins go into the vein sinusoid. Left, medium and right portal vein each go into left, medium and right leaf of liver and there are liaison vessels that send out 6~8 small veins of directly going into the liver between the 3 portal veins. Every leaf of liver sends out hepatic ducts that open into the cystic duct. After hepatic ducts and the cystic duct are joined together and the relatively enlarged common bile duct that opens into the forepart of intestines near the stomach isformed.On the 3 fishes, the livers are each enveloped by a thin layer of chorion. The hepatic lobules are not obvious. The Kupffers cells can be seen rarely.On C. alburnus, central veins are very irregular and the hepatocyte cord that is composed of a few lines of hepatocytes is partly obvious. Hepatic sinusoids form webs. Boundaries of hepatocytes are clear and binuclear hepatocytes can be seen rarely. Large numbers of adipose-cell-like hepatocytes that get together to form some gobbets are found in hepatic parenchyma. Vessels and bile ducts in the liver are rather developed. Veins and arteries entered the liver each first branch into interlobular veins and interlobular arteries, then microveins and microarteries are branched out repeatedly;microveins and rnicroarteries join into hepatic sinusoids, central veins, sublobular veins, all levels of branch veins, central veins of leaf of liver, veins of liver at last. Bile excreted by hepatocytes fist flows into bile canaliculuses, then endolobular bile ducts, interlobular bile ducts, all levels of branch bile ducts, central bile ducts of leaf of liver, hepatic ducts at last.On M. macropterus, central veins are either big or small and hepatocyte cords loom. Boundaries of hepatocytes are relatively clear. Hepatic sinusoids form webs of honeycomb. Hepatocytes are divided into 2 kinds. One contains more-adipose hepatocytes that are mainly distributed in hepatic parenchyma near the porta hepatis and the other less-adipose hepatocytes. vessels in the liver are very developed. The blood circulation is similar to that of C. alburnus, but there are not central veins in leaves of liver. The bile flow is also similar to that of C. alburnus, but every level of bile ducts above the bile canaliculus are not relatively developed and there are not central bile ducts in leaves of liver.On 5. scherzeri, central veins are either big or small and hepatocyte cords can not be told apart. Hepatic sinusoids weave into webs and knots are a little enlarged. Boundaries of hepatocytes are not very clear. Like M. macropterus, hepatocytes are plotted out more-adipose ones and less-adipose ones, and more-adipose hepatocytes are very developed. Every level of vessels and bile ducts above the the bile canaliculus are not relatively developed. Blood circulation and bile flow are similar to those of M. macropterus.Hepatocytes of M. macropterus and S. scherzeri have obvious dimorphism from the observation of ultrastructure. That is, hepatoytes are composed of light cells and dark cells according to their own electron density of cytoplasm. In hepatocytes of the 3 fishes, euchromatin is abundant in the nucleus and the nucleolus is rather big;there are abundant mitochondria and ribosomes, developed endoplasmic reticulum (in particular rough endoplasmic reticulum), a few patterns of lysosme, a quantity of glycogen and fat in cytoplasm. The characteristics of hepatocytes are adaptable to the 3 fishes' meat-eating behavior.The pancreas of C. alburnus belongs to the diffuse type, and it is made up of many loose grains, mainly distributed on the mesentery between the forepart of liver and the digestive tract. The pancreas of M. macropterus belongs to the suffusion-mix type, and it is made up of many loose grains and bead-shaped strings, mainly distributed on the mesentery among porta hepatis, stomach and intestines;what is more, pancreatic tissue is distributed both on the surface of the liver near vessels at the porta hepatis and around vessels in hepatic parenchyma near the porta hepatis. The pancreas of S. scherzeri belongs to the disperse-compact type, and it is made up of many compact grains, concentrated on the mesentery among porta hepatis, stomach and forepart of intestines.On the 3 fishes, Pancreases are each made up of exocrine sections and pancreatic islets, and the exocrine sections consist of pancreatic alveoli and gland ducts. Boundaries of Pancreatic cells are obvious. Centro-acinar cells cling to the walls of cavity of pancreatic alveoli. Gland ducts are made up of intercalated ducts, endolobular ducts, interlobular ducts and gathering ducts from the first to the last. Pancreatic islets that are encircled by connective tissue belong to the isle-like type and scatter in the exocrine sections of pancreas. We observed only A cells and B cells in Pancreatic islets and B cells are much superior to A cells.The chorion of Pancreas of C. alburnus is thin and pancreatic lobules are not clear. Pancreatic islets are relatively small and scattered and the number of unit area is relatively small. The chorion of Pancreas of M. macropterus is thin but pancreatic lobules are obvious. Pancreatic islets are relatively large and scattered and the number of unit area is relatively small. The chorion of Pancreas of S. scherzeri is thick and pancreatic lobules are obvious. Pancreatic islets are relatively large and concentrated and the number of unit area is relatively large.On the base of morphological studies on livers and pancreas of the 3 fishes, Blood circulation pathway of liver, pancreatin and bile flows of teleostean are investigated and described by the numbers in this dissertation. Meanwhile, some relevant terms such as central vein of leaf of liver, branch vein, central bile duct of leaf of liver, branch bile duct and gathering duct are also putted forward. Furthermore, hepatocytes of meat-eating teleostean are divided into 3 types on the microstructural level, namely adipose-cell-like, more-adipose and less-adipose ones;pancreases of teleostean are divided into 4 types, namely compact, disperse-dense, diffuse and suffusion-mix type.