The kidney maintains homeostasis by regulation of fluid and electrolyte balance, as well as the elimination of nitrogenous and toxic products. The kidney has adapted an intricate vascular network that contains as much as 20 percent of the cardiac output at any given time. This high throughput is critical to the function of the glomerular capillaries, which filter the fluid component of blood. Fluid and electrolytes filtered at the glomerulus are reabsorbed by the nephron and mostly returned to the circulation. The glomerular capillaries are located exclusively in the cortex and give rise to cortical (superficial) and juxtamedullary nephrons. Cortical nephrons have short loops of Henle passing only a short distance into the medulla. Juxtamedullary nephrons, with long loops of Henle, pass deep into the medulla to the papilla. Cortical glomeruli give rise to short efferent arterioles that pass into a peritubular capillary that bathes the proximal tubule of cortical nephrons and is structurally similar to nonrenal capillaries. Juxtamedullary glomeruli also give rise to efferent arterioles, some of which lead to peritubular capillaries and some that lead directly to small venules, the vasa recta. The main determinant of filtration, glomerular capillary hydrostatic pressure, is tightly regulated by the highly resistant afferent and efferent arteri-oles, which are subject to humoral, neural, and physical factors. In this review, I will summarize studies that make new and important observations on renal cortical microcirculation and are representative of recent research in this area.
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