Urea in our body

Urea is a waste product. It is found in our body and extracted from urine. However, it also plays a very important role in that it helps set up the countercurrent system in the nephrons. Urea is reabsorbed in the inner medullary collecting ducts of the nephrons, thus raising the osmolality in the medullary interstitial surrounding the thin ascending limb of the Loop of Henley. The greater the osmolarity of the medullary interstitium surrounding the thin ascending Loop of Henle, the more water will be reabsorbed out of the renal tubule back into the interstitium (and thus back into the body). 



Some of the urea from the medullary interstitium that helped set up the Countercurrent System will also flow back into the tubule, through urea transporter 2, into the thin ascending limb of the loop of Henle, through the collecting ducts, and eventually out of the body as a component of urine.