Excretion and Fluid Balance in Vertebrates


Vertebrates have adapted to large variations in environmental conditions in each of which the internal environment of volume and solute composition must be maintained within narrow limits. In mammals, some 80–90% of the total osmolality is made up of sodium and chloride ions. To maintain their highly regulated internal environments, animals must be ‘in balance’ – a state termed homeostasis that is achieved through complex positive and negative feedback mechanisms.

Keywords: urinary excretion in vertebrates; fluid balance in vertebrates; osmotic regulation; nephron; kidney

Further Reading

Dantzler WH (1992) Comparative physiology of the kidney. In: Windhager EE (ed.). Handbook of Physiology, pp. 415–474. Oxford: Oxford University Press.

Luke RG (2000) Chronic renal failure. In: Goldman L and Bennett JC (eds). Cecil Textbook of Medicine, 21st edn., pp. 571–578. Philadelphia: WB Saunders.

Sands JM (1999) Regulation of renal urea transporters. Journal of the American Society of Nephrology 10: 635–646.

Sands JM and Kokko JP (1996) Current concepts of the countercurrent multiplication system. Kidney International 50 (supplement 57): S93–S99.

Schmidt‐Nielsen B (1987) The renal pelvis. Kidney International 31: 621–628.

Sterns RH, Spital A and Clark EC (1996) Disorders of water balance. In: Kokko JP and Tannen RL (eds). Fluids and Electrolytes, 3rd edn., pp. 63–109. Philadelphia: WB Saunders.

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Kokko, Juha P(Apr 2001) Excretion and Fluid Balance in Vertebrates. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0001841]