ABSTRACT
The mechanism by which urine is formed has been of great interest in science and medicine. Understanding the mechanism by which urine is formed gives a basis for understanding many of the abnormalities of urine that are observed in disease. The earliest concepts of the mechanism of urine formation involved the idea that tissue melted or was converted into urine in what may roughly be regarded as a process comparable to the mechanism by which ice melts and is converted to water. The basic, microscopic functional unit of the kidney is the nephron. The kidneys receive a very great supply of blood from the abdominal aorta through the renal arteries. The arteries subdivide and ultimately become arterioles which enter the glomeruli in the renal cortex. The length of time that urine remains in the bladder varies from a few minutes to several hours. In the majority of instances the urine is acid, but in some cases it is alkaline.
