Answer: the glomerular endothelium cells, the basement membrane, and the Podocyte processes...
Explanation:
The formation of urine by the kidneys occurs in 3 stages described at following:
- Glomerular Filtration - It is the 1st stage in the formation of urine. In this step large amount of liquid is filtered through the membrane from glomerular capillary to Bowman's capsule;
- Tubular Resorption - At this stage, water and some solutes are reabsorbed from the tubules into the blood;
- Tubular Secretion - In this last step occurs the secretion of substances from the blood to the tubules.
This first stage occurs in the glomerular capillaries where part of blood that reaches the glomerulus is forced to pass under pressure by a filtering barrier. This barrier is called the glomerulus filtration membrane. The glomerulus filtration membrane consists of 3 layers, two of them from the capillary (basal membrane and endothelium), and one formed by Bowman's capsule epithelial cells. The endothelial layer, as in the other capillaries, has thousands of pores called fenestrations. These pores allow the passage of all plasma except blood cells. Already the basement membrane is formed by a tangle of protein fibers that prevent the passage of larger proteins. Finally, the outermost layer is formed by the epithelial cells. Bowman's capsule protruding over the basement membrane. These cells are called podocytes since their projections resemble feet.
