Kidneys :: essays research papers

KidneysIn vertebrates, kidneys are the deuce major organs of excretion. exorbitance pissing, toxic waste products of metabolism such(prenominal) as urea, uric acid, and inorganicsalts are disposed of by kidneys in the form of urine. Kidneys are also for the most partresponsible for maintaining the water balance of the dead body and the pH of theblood. Kidneys play important roles in other bodily functions, such asreleasing the erythropoietin protein, and helping to laterality blood pressure.Kidneys are paired, reddish-brown, bean-shaped structures. They areabout eleven centimeters long. Kidneys are located on each side of spine, justabove the waist. They are loosely held in place by a mass of fat and two layersof fibrous tissue. It is believed that the kidney first evolved in the originalvertebrates where freshwater organisms needed some means of pumping water fromthe body. The kidney became adept at reabsorbing glucose, salts, and othermaterials which would have been lost if sim ply pumped out of the body by asimple organ.The cut surface of the kidney reveals two distinct areas the cortex- adark band along the outer border, about unmatchable centimeter in thickness, and theinner medulla. The medulla is divided into 8 to 18 cone-shaped masses of tissuenamed renal gains. The apex of each pyramid, the papilla, extends into therenal pelvis, through which urine is released from the kidney tissue. Thecortex arches over the bases of the pyramids (cortical arches) and extends downbetween each pyramid as the renal columns.Urine passes through the body in a fairly complex way. The initial siteof urine production in the body is the glomerus. The arterial blood pressuredrives a filter out of plasma containing salts, glucose, amino acids, andnitrogenous wastes such as urea and a small amount of ammonia through theglomerus. Proteins and fats are filtered out of the plasma, to remain in thenormal blood stream. The plasma is now called glorular filtrate. One-hundredto one-hundred-forty milliliters of this filtrate are formed each minuteThe filtrate passes along a convoluted tibule. The majority of thewater content and some of the dissolved materials are reabsorbed through thewalls of the tibule and back into the blood. Water, sodium, chloride,bicarbonate, and all glucose are reabsorbed into the bloodstream, yet productssuch as urea and ammonia remain in the tibule. During the final stage of thepassage process, most of the remaining filtrate is selectively reabsorbed untilonly about one percent of the original filtrate is to be excreted as urine.Urine is eventually collected in the kidneys. The urine is collected in