How Does the Kidney Filter Plasma?

摘要

The kidneys filter the plasma in special filtration units—glomeruli—and thereby excrete low-molecular-weight waste products into the urine. The mechanisms of giomerular filtration have been a matter of controversy for several decades, but recent data have revealed new details about the molecular nature of the filter and have demonstrated a central role for the podocyte slit diaphragm in the filtration process. The main function of kidney glomeruli is to filter low-molecular-weight plasma waste products into the urine while restricting the passage of albumin and larger macromolecules that are necessary for maintaining normal homeostasis. Every day, -180 liters of primary urine devoid of macromolecules is normally formed in the human kidneys, each of which has -1,000,000 glomeruli. The primary urine is extensively modified in the renal tubular system in regard to composition and volume, so that the final daily excretion is normally only -1-1.5 I/day.