| Objective To investigate the developmental and morphologicalcharacters of the mesenteric lymphatics in Wistar rat.Methods The developmental and morphological characters of the mesenteric lymphatics of 183 Wistar rats were studied by using light microscope, en2yme-histochemistry, TEM and injection of Pontamine sky blue.Results (1) The blood circulation of mesentery was established on day 16 during pregnancy, but no "sprout" was found from the blood vessels and then formed the lymphatics during the period of pregnancy.(2) The mesenteric lymphatics appeared on day 18 during pregnancy and the valves appeared on day 0 after birth.(3) The distribution of mesenteric lymphatics varied on different mesenteric parts and ages.(4) There were obvious differences in ultrastructure of the lymphatic endothelia between the embryonic and the adult rats.Conclusion (1) No blood vessels were found to differentiate and become the lymphatics in the mesentery of fistar rat, and this suggested that the lymphatic might develop from the mesenchymalcells in the tissue. Our results showed the mesenteric lymphatics developed "centripetally" .(2) There were obvious morphological differences for the mesenteric lymphatics in the different parts, and this illustrated that the structural character decided the function.(3) There might be some differences of ALPase system in the blood vessels between the embryonic and the adult rats.
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