Reabsorption, the regulation of urine osmolarity and action of vasopressin (ADH). Basically, how all the stuff that gets filtered (removed from the blood in the renal corpuscle) gets BACK to the blood a few seconds later. More about the renal system: Glomerular Filtration: https://www.youtube.com/watch?v=IWwftdhUslA the RAAS: https://www.youtube.com/watch?v=xdYILlD6R3s Want more? Subscribe: null FB Page: https://www.facebook.com/ThePenguinProf Twitter: https://twitter.com/penguinprof Web: http://www.penguinprof.com/