are the two organs located in the back of the abdomen
, near the lower two thoracic vertebra
and the first two lumbar vertebra
, one on each side of the spinal column. The right kidney
is typically located slightly lower than the left. On average, a kidney measures 12 centimeters by 6 and is 3 centimeters thick, but it can decrease in size in cases of chronic kidney failure. Within the structure of the kidney there is the nephron, through which the blood
circulates and certain molecules considered waste are filtered out. The resulting primary urine then circulates through different channels whose walls can be penetrated by different substances. Subjected, thus, to the influence of hormones, reabsorbed water, and other molecules, the composition of primary urine is altered to become what is recognized as normal urine, which then flows into the urethra
, the channel joining the bladder.