Glomerular Filtration

THE structural and functional unit of the kidney is the nephron. There are approximately one million nephrons in a single human kidney, each consisting of a single glomerulus of capillaries and an attached renal tubule. The elaborate tangle of interconnecting capillaries that forms a glomerular tuft has been shown beautifully in an earlier article in this series.1 The entire capillary tuft is enclosed by an epithelial capsule (Bowman's capsule), which is continuous with an epithelial sheath that invests the glomerular capillaries on the one hand and the lining epithelium of the proximal convoluted tubule on the other (Fig. 1). As . . .