Blood entering glomerulus carries urea molecule, and the molecules are filtered through Bowman's capsule and then it enters the proximal convoluted tubules. The half of incoming urea is being reabsorbed and it enters the loop of Henle's. Urea is being secreted in thin limbs of a loop from the medulla into the lumen of the tubules increasing urea concentration to hundred percent.
From loop, the urea enters to distal convolated tubules (DCT) being hundred percent. In distal convoluted tubules, thirty percent is reabsorbed to cortex while the remaining seventy percent enters to collecting tubules. Fifty percent is being reabsorbed in the medulla. Fifteen percent is excreted as urine, the five percent is reabsorbed by vasa recta and arteries which are associated with nephron.
The urea recycling traps most of the urea in the medulla and it creates high osmolarity which helps in water reabsorption.
