Renal urea handling is the part of
renal physiology that deals with the
reabsorption and
secretion 440px
Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical ...
of
urea. Movement of large amounts of urea across cell membranes is made possible by
urea transporter proteins.
Urea allows the
kidneys 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 must save water in order to maintain a suitable
blood pressure
Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...
or (more likely) in order to maintain a suitable concentration of
sodium ions in the blood plasma.
About 40% of the urea filtered is normally found in the final urine,
[ since there is more reabsorption than secretion along the nephron.
It is regulated by ]antidiuretic hormone
Human vasopressin, also called antidiuretic hormone (ADH), arginine vasopressin (AVP) or argipressin, is a hormone synthesized from the AVP gene as a peptide prohormone in neurons in the hypothalamus, and is converted to AVP. It then travel ...
, which controls the amount reabsorbed in the collecting duct system
The collecting duct system of the kidney consists of a series of tubules and ducts that physically connect nephrons to a minor calyx or directly to the renal pelvis. The collecting duct system is the last part of nephron and participates in elect ...
and secreted into the loop of Henle.
Overview table
References
{{renal physiology
Renal physiology