Renal Biophysics

The kidneys are vital to the maintenance of equilibrium between the food and drink we consume and the excretion of fluid in the form of urine. We also lose fluid through perspiration and, to a lesser extent, respiration. The kidneys and associated control systems are able to monitor fluid balance and, by extension, circulatory blood volume. In more primitive animals, such as amphibians, the skin is also a major component in the regulation of fluid balance, so a portion of what is now known about the function of the human kidney has been inferred from the effects of hormones and other agents on the rate of ion transport across amphibian skin. In Chapter 3, the importance of measuring short-circuit current was highlighted.