A Simulation of the Control of Excretion in the Distal Portion of the Dog\u27s Kidney

The excretion of metabolic waste products is of prime importance to the life and well being of all living things. In man and animals this process is carried out by the kidneys, the lungs, the skin, and the bowel. The largest excretion of water and other waste products is accomplished by the kidney. In higher forms of animal life there are two such structures and each is composed of hundreds of thousands of basic units called nephrons. The function of such nephrons is to clear the blood plasma of unwanted substances as it passes through each structure. These unwanted substances are excess constituents of blood plasma and metabolic waste products. Formation of urine by the kidney may be viewed as the summation of the functions of many individual nephrons. Extensive research has been performed on various segments of the nephron to determine how each processes the urine. Some clinical data is available to describe the filtration, secretion, and reabsorption patterns of various substances in the nephron. Information is also available which depicts the concentration of these substances in the interstitial spaces between nephrons. In this thesis, information has been incorporated into a mathematical description of the fate of sodium, potassium, urea, and water in the more distal part of the nephron. Discussion will be limited to the dog\u27s kidney which has been extensively studied. The urine concentrating and diluting mechanism, which results from two extreme physiological states commonly studied in the laboratory, will be modeled. It is the purpose of this thesis to investigate the nature and magnitude of controlling parameters of the model