Kidney Kidney The kidneys are two bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about 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. The nephron is the structural and functional unit of the kidney. Each adult kidney contains around 1 million nephrons. The nephron utilizes four processes to alter the blood plasma which flows to it: filtration, reabsorption, secretion, and excretion. The
Artery is the root systemic artery (i.e., main artery). In humans, it receives blood directly from the left ventricle of the heart via the aortic valve. As the aorta branches, and these arteries branch in turn, they become successively smaller in diameter, down to the arterioles. The arterioles supply capillaries, which in turn empty into venules. The very first branches off of the aorta are the coronary arteries, which supply blood to the heart muscle itself. These are followed by the branches off the aortic arch, namely the brachiocephalic artery, the left common carotid, and the left subclavian arteries. The capillaries