Biophysics of glomerular filtration

Enlightened by William Bowman's depiction of the anatomy in 1842, Carl Ludwig immediately proposed glomerular filtration as a physical process. Nuances of this process have come to light in a rather orderly progression over the past 150 years with essential contributions from clearance methods, renal micropuncture, physical theories of nonequilibrium thermodynamics and electrical double layers, morphometry, and mathematics. Herein, we describe that progression of knowledge. Ongoing work pertains to the nature, location, and efficiency of the barrier to protein sieving, induction of endothelial fenestrae by growth factors from the podocyte, and potential resistance faced by filtrate exiting the subpodocyte space.