The blood water and its solutes are filtered into the glomerulus through the glomerulus to form urine, which must pass through the endothelial cell, basement membrane and epithelial cell of the capillary wall. These three structures are called glomerular filtration membranes.
The three layer filtration membrane has a certain pore, can only allow a certain molecular weight and the diameter of the material through the filtration membrane, thus constituting the aperture barrier, and the surface structure of three layers were coated with sialic acid protein, glomerular basement membrane inner and outer loose layer with heparan sulfate, these substances with negative charge in the human body environment in the exclusion of solute with negative charge through, so as to form the charge barrier filtration membrane.
In addition, the glomerular mesangial system located between the glomerular capillaries has a regulatory effect on the glomerular filtration barrier and thus plays a role in the filtration of the glomerulus.
Under normal circumstances, the vast majority of the blood. Proteins can not pass through the glomerular filtration barrier, especially large molecules and albumin with negative albumin, which can hardly pass through, and small amounts of proteins that are absorbed through the filtration membrane can be reabsorbed in the renal tubules.
Thus, although approximately 10 to 15kg per day, plasma proteins flow through the renal circulation. But the protein excreted from urine is less than 150mg. In nephrotic syndrome, due to a variety of pathological factors, the barrier function of filtration membrane is damaged, such as pore size or negative charge is reduced, resulting in a large number of protein leakage, heavy absorption capacity and far more than the renal tubules, so there will be a large number of proteinuria.
Beijing In China