Kidney anatomy, kidney structure and nephrons in section. The left kidney (in blue) is shown in section with the nephrons (in orange-yellow). The internal vascularization of the kidney is enhanced in the cortex. The kidney is an organ that filters blood and produces urine. The renal parenchyma contains the nephrons which filter the blood and produce the urine. Thus, the urine produced in the nephrons is collected at the level of the chalices and pelvis (in dark blue). They are prolonged by the ureter which will convey the urine to the bladder, except the bladder is not shown in this drawing, because it is located much lower in the anatomy of the urinary system.