Figure 1.

Medullary microcirculation. Juxtamedullary glomeruli originate at an acute angle from the interlobular artery. Most blood flow into the medulla arises from juxtamedullary efferent arterioles. At the outer stripe of the outer medulla, juxtamedullary efferent arterioles progress into descending vasa recta [DVR] and form vascular bundles at the inner stripe of the outer medulla. DVR around the exterior of the vascular bundles perfuse the interbundle capillary plexus that supplies nephrons. DVR in the centre of the bundles continue across the inner–outer medullary junction to perfuse the inner medulla. The vascular bundles disappear in the inner medulla with the vasa recta becoming dispersed between thin loops of Henle, collecting ducts, and ascending vasa recta [AVR]. AVR ascend to the cortex through outer medullary vascular bundles. DVR have a continuous endothelium (left inset) and are surrounded by contractile pericytes. AVR are highly fenestrated vessels (right inset). Taken from Navar et al. (2008), 550–683. Fig. 13.11, p. 567.