Peculiarities of extraorganic renal veins branching in the snowy owl
The conducted studies showed that in the snowy owl the blood from the pelvic extremities is collected by the right and the left external iliac veins into the pelvic cavity, going from the caudal portal vein of the kidney branches. Blood is collected from the cranial part of the kidneys along the cranial portal veins, and along the caudal portal vein -from the middle and the caudal lobe of the kidneys. The caudal right and left portal veins join together and from the junction the caudal mesenteric vein emerges, which collects blood from the intestine, then flowing into the liver. The right and left renal veins, which have the same diameter, flow along the entire length of the kidney, perform a uniform transportation of venous blood from the middle and caudal parts of the kidneys, and connect to each other at an angle of 38o, flow into the common iliac vein, which, in turn, joins the caudal vena cava. It is noted that the venous blood of the snowy owl simultaneously flows through three different vessels, but always in one direction and the outflow of blood from the kidneys takes place in three ways. The first way is carried out on the renal veins from the middle and caudal parts of the kidney, flowing into the common iliac vein, and then into the caudal vena cava. In the second way blood is passes along the coccygeal-mesenteric vein into the liver. The third way is along the right and left cranial portal veins from the cranial part of the kidney into the vertebral venous canal. It was established that two systems of renal portal veins of the right and left sides join together, forming a closed ring. Venous blood entering the external iliac veins of both sides, pass into the portal vein system, causing intravascular pressure, and due to the presence of a group of valves, blood always flows in one direction. Only between the renal and portal renal veins anastomoses are formed, developing a double network of capillaries.