[Structural organization of the tubular component of the renal countercurrent system].
The time course of the developing tubules of the dog kidney in the prenatal period of ontogenesis was studied by the methods of microscopy and three-dimensional reconstruction. It was established that the structural functional unit of the osmoregulatory system is a cone-shaped fascicle whose central axis is a collecting tubule. Henle's loops of three juxtamedullary nephrons and accompanying blood vessels are grouped concentrically along the axis. The tubules are grouped in such a manner that the most central position is occupied by the ascending portions of the loop while the descending ones lie somewhat outwards.