Basic structure of the glomerulus and the glomerular filtration barrier. Basic structure of the glomerulus and the glomerular filtration barrier. (A) Each glomerulus is composed of an afferent arteriole, which supplies the glomerular capillaries, and an efferent arteriole, into which they drain. Mesangial cells and mesangial matrix provide structural support for the glomerular capillaries, lined by specialized fenestrated endothelium, and then the glomerular basement membrane. On the urinary side of the glomerular basement membrane are podocytes, with foot processes that wrap around the glomerular capillaries. The urinary space is lined by a cup-like layer of parietal epithelial cells which adhere to the basement membrane of Bowman’s capsule. (B) The glomerular filtration barrier is a specialized molecular sieve, with properties that aid filtration of small solutes from the blood to the urine, while limiting the passage of macromolecules such as albumin. A. Richard Kitching, and Holly L. Hutton CJASN 2016;11:1664-1674 ©2016 by American Society of Nephrology