The renal microcirculation
The renal medulla is not inhabited solely by the renal tubules, there is also notably the renal micro-circulation.
This starts in the form of the descending vasa recta (DVR), which take a strikingly straight path deep into the medulla. At various points throughout its depth, the DVR branches into fine capillaries. These capillaries spread through the medulla and anatomise to form the efferent vessels.
One of the primary functions of the renal micro-circulation is that of nutrient provision and metabolite exchange for purposes of maintaining cellular function of those tissues making up the renal medulla.
The permeability dillema