The answer is Loop of
Henle. It is the portion of a nephron that leads from the proximal convoluted
tubule to the distal convoluted tubule. While the loops of Henle of cortical
nephrons penetrate only as far as the outer medulla of the kidney, those of the
juxtamedullary nephrons penetrate deeply within the inner medulla. The juxtamedullary
nephrons are largely responsible for
developing the osmotic gradients that are needed to concentrate urine.
