Glomerular Filtration Layers: A Detailed Explanation

The glomerular filtration barrier comprises three layers:

1. Fenestrated endothelium: Glomerular capillary endothelial cells with 70–100 nm pores; permeable to water/solutes, retains cells.
2. Glomerular basement membrane (GBM): Acellular matrix of collagen IV, laminin, nidogen, heparan sulfate; major size/charge barrier.
3. Visceral epithelium (podocytes): Interdigitating foot processes with filtration slits (slit diaphragm); final size-selective barrier.

Together, they permit water and small solutes while restricting albumin and larger proteins. Damage to any layer causes proteinuria.