Why is the glomerulus referred to as a non-selective filter?

1 Answer
Sep 20, 2016

The main function of the glomerulus is to filter plasma and produce glomerular filtrate , which passes through the length of the nephron tubule to form urine.


Urine formation begins with glomerular filtration, which is a non selective process in which fluids and solutes are forced through a membrane by hydrostatic pressure.

The factors determining the permeability and selectivity of the glomerulus are
1) presence of negative charge on the basement membrane,
2) effective pore size of the glomerulus membrane.

The filtration membrane of the glomerulus is therefore thousands of times more permeable to water and solutes than other capillary membranes.

As a result small positively charged molecules will pass through freely. Example - small ions like sodium and potassium pass freely but, haemoglobin and albumin have practically no permeability.

Thus glomerular filtration is non selective as , though all substances must move through the glomerular membrane i.e. plasma and dissolved substances but no blood cells and large blood proteins.