What is the role of the Loop of Henle in urine production?

The Loop of Henle is a 'U' shaped portion of the nephron tubule which is very important in retaining water and Na+ from urine, in the process of 'Osmoregulation'. Water leaves the descending limb of the Loop of Henle by osmosis, increasing the concentration of Na+ inside the limb, so the ascending limb receives a high concentration of Na+ filtrate. This causes the ascending limb to pump out Na+ by active transport into the surrounding area called the Medulla. The Medulla now has a lot of Na+ as well as just water molecules, which means it has a lower water potential. As a result, the ascending limb of the Loop of Henle retains all water molecules inside the Loop. The Loop has created an osmotic balance and will pass its filtrate to the collecting duct where it will travel to the bladder.