The structural and functional unit of the kidney is the

Explanation

Each kidney contains about a million nephrons, and every one carries out filtration, reabsorption and secretion on its own, so the organ's work is the sum of theirs. A nephron runs from the Bowman's capsule through the proximal tubule, loop of Henle and distal tubule to a collecting duct. The ureter merely carries the finished urine to the bladder, and the neuron belongs to the nervous system.