The work of the kidneys presents a photoghaphic record of the many functions of the urinary system. Difficult concepts are clarified through the use of animated drawings and skillful photomicrography.
The opening sequence briefly explains how the kidneys maintain uniformity in the blood and tissues , keeping the water content , salt concentration, acidity, and osmotic pressure at the levels optimum for life. Another important function of the kidneys is to eliminate wastes and other substances which, though normally present in the blood, might become toxic if they were to reach a high level of concentration
The main functional parts of the kidneys the glomerulus and the tubule are shown in animated drawings. the glomerulus is a special kind of filter. Blood passes through it in a fine capillary with walls which constitute a semi permeable membrane. The fluid filtered off from the blood is normally just like plasma, except that it has little or no protein. The amount of blood filtered through the glomerular filtrate is directly dependent on the blood pressure. the glomerular filtrate passes down the long tubule lined with special cells which reabsorb into the blood stream some, but not all of the substances in the glomerular filtrate. Most of the water is absorbed. Other substances, like salt and sugar, are mostly reabsorbed. Any excess is secreted into the urine. Thus, a normal composition of these essential substances in the blood is assured.
Some of the factors affecting urine formation are studies in tests on anesthetized dogs. When a quart of blood is taken from a dog, its blood pressure drops and urine formation is decreased. When the urine flow is increased by an injection of urea into the animal's blood composition constant by removing the excess urea.
Since a kidney, even when removed from the body, continues to secrete urine in a limited way for some time, it clear that the kidney cells carry on their function independent of other bodily controls.
The function of the bladder is illustrated with stop - motion photography. Urine passes from the microscopic tubules into larger collecting tubes, then from each kidney into the ureters and finally , by peristaltic by urine, nerve impulses from the bladder pass to the spinal cord and brain, starting nerve impulses which relax the sphincters and cause contraction of the bladder muscles, to force out the urine.
The film points out, in conclusion that the function of the kidneys is to maintain a balanced composition of blood and tissue in the face of reverse influences in the processes of living, in health and disease