The blood enters the Bowman's capsule into the glomerulus through the afferent arterioles of the renal circulation. This is the vessel that brings blood into the Bowman's capsule. The filtered blood leaves the glomerulus through the efferent arteriole.
The principle nitrogenous excretory compound in humans is urea. Urea is produced in a series of reactions (urea cycle) which take place in the mitochondrial matrix and cytosol of liver cells.