What is the functional unit of the kidney?

The nephron is considered the functional unit of the kidney because it is the smallest structural and functional component that is capable of performing the essential processes of filtration, reabsorption, secretion, and excretion of waste products. Each kidney contains approximately one million nephrons, which work together to filter blood, remove waste, and regulate electrolyte balance, blood pressure, and acid-base homeostasis.

Each nephron consists of several components, including the glomerulus (which is responsible for the initial filtration of blood), the renal tubule (where reabsorption and secretion occur), and the collecting duct (where urine is collected before it moves to the renal pelvis). While structures like the glomerulus and collecting duct are important parts of the nephron, they do not function independently to perform all the critical functions associated with kidney activity. The renal pelvis serves as a funnel for urine flowing towards the ureter but is not involved in the functional processes of filtering and processing blood.

Thus, identifying the nephron as the functional unit emphasizes its holistic role in kidney function, critical in maintaining homeostasis and overall health.