The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about 12 centimetres (4+1/2 inches) in length. They receive blood from the paired renal arteries; blood exits into the paired renal veins. Each kidney is attached to a ureter, a tube that carries excreted urine to the bladder. <img src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/ab/KidneyStructures_PioM.svg/1024px-KidneyStructures_PioM.svg.png" height="500"> From [Wikidepia](https://en.wikipedia.org/wiki/Kidney) under [CC BY-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0/) license.