NBME Histology Practice Test 2026 – The Comprehensive Guide to Mastering Your Exam Success!

The glomerular filtration barrier is a three-layer structure: fenestrated endothelium, the glomerular basement membrane, and podocyte slit diaphragms. The endothelial layer has pores that let plasma through while blocking blood cells. The basement membrane acts as a size- and charge-selective sieve, restricting larger proteins. The podocytes with their interdigitating foot processes form filtration slits bridged by slit diaphragms, providing the final barrier to large molecules and helping maintain charge selectivity. Mesangial cells provide structural support and phagocytic clearance, but they are not part of the filtration barrier itself.

So the combination of fenestrated endothelium, glomerular basement membrane, and podocyte filtration slits best describes the filtration barrier.