Histological study of renal portal valve was carried out on 10 Kidneys of mature healthy Arian roosters. In order to preservation of the valves, veins were taken in accompanied with caudal half part of the cranial lobes up to cranial half of the middle lobes and from the ventral surfaces of both right and left kidneys, then fixed in 10% buffered formalin. Routine hisi:ological method was used and paraffin blocks were made. 6 m thick sections were cut longitudinally and stained with haematoxylin — eosin and orcein and studied under light microscope. Our histological observations suggest that the renal portal valve is a conical prominence inside the external iliac vein lumen. Increasing the thickness of all 3 tunica of vein’s wall namely, tunica intimae, tunica media and tunica adventitia observed. Congregation of epitheloid cells in subendothelial connective tissue of tunica intimae, increasing of smooth muscle cell layers of tunica media and increasing the elastic fibers in the tunica adventitia were observed.
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