<unk>  is the part of<unk>  physiology that deals with the reabsorption and secretion of<unk> .<unk>  allows the body to create hyperosmotic urine (urine that has more ions in it--is "more concentrated"--than that same person's blood plasma). Preventing the loss of water in this manner is important if the person's body needs to save water in order to maintain a suitable blood pressure or (more likely,) in order to maintain a suitable concentration of sodium ions in the blood plasma.
About half of the<unk>  filtered (40%) is normally found in the final urine, since there is more reabsorption than secretion along the nephron.
It is regulated by antidiuretic hormone, which controls the amount reabsorbed in the collecting duct system and secreted into the loop of Henle.
Renal urea handling
Renal protein reabsorption
Renal glucose reabsorption
Renal oligopeptide reabsorption
Renal chloride reabsorption
Renal blood flow
Hypothalamic pituitary adrenal axis
Renin-angiotensin system