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Renal urea handling

Renal ura handling is the part of renal physiology that deals with the reabsorption and secretion of urea.

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Urea 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 urea filtered (40%^[1]) 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.

Overview table

Characteristic	proximal tubule			loop of Henle			Distal convoluted tubule	Collecting duct system
Characteristic	S1	S2	S3	descending limb	thin ascending limb	thick ascending limb	Distal convoluted tubule	connecting tubule	initial collecting tubule	cortical collecting ducts	medullary collecting ducts
reabsorption (% compared to filtered amount)	50^[1]										70
secretion (% compared to filtered amount)					60^[1]
reabsorption (mmoles/day)
Concentration
electrical driving force (mV)	-3^[2]		+3^[2]			+15^[2]	-5 to +5^[2]			-40^[2]
chemical driving force (mV)
electrochemical driving force (mV)
apical transport proteins	solvent drag^[1] unknwn transporter^[1]			Urea transporter 2?^[1]	unknwn transporter^[1]						urea transporter 1^[1]
basolateral transport proteins	unknown transporter^[1]			Urea transporter 2?^[1]	unknwn transporter^[1]						urea transporter 4^[1]
Other reabsorption features

References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l Walter F., PhD. Boron. Medical Physiology: A Cellular And Molecular Approaoch. Elsevier/Saunders. ISBN 1-4160-2328-3. Page 791
^ ^a ^b ^c ^d ^e Walter F., PhD. Boron. Medical Physiology: A Cellular And Molecular Approaoch. Elsevier/Saunders. ISBN 1-4160-2328-3. Page 777

v • d • e Urinary system, physiology: renal physiology and acid base physiology
Filtration	Renal blood flow - Ultrafiltration - Countercurrent exchange
Hormones affecting filtration	Antidiuretic hormone (ADH) - Aldosterone - Atrial natriuretic peptide
Secretion/clearance	Pharmacokinetics - Clearance of medications
Reabsorption	Solvent drag -Na⁺ - Cl^- -urea -glucose -oligopeptides -protein
Endocrine	Renin - Erythropoietin (EPO) - Calcitriol (Active vitamin D) - Prostaglandins
Assessing Renal function / Measures of dialysis	Glomerular filtration rate - Creatinine clearance - Renal clearance ratio - Urea reduction ratio - Kt/V - Standardized Kt/V - Hemodialysis product - PAH clearance (Effective renal plasma flow - Extraction ratio)
Acid base physiology	Fluid balance - Darrow Yannet diagram - Body water - Interstitial fluid - Extracellular fluid - Intracellular fluid/Cytosol - Plasma - Transcellular fluid - Base excess - Davenport diagram - Anion gap - Arterial blood gas
Buffering/compensation	Bicarbonate buffering system - Respiratory compensation - Renal compensation

Category: Physiology

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Renal_urea_handling". A list of authors is available in Wikipedia.