What is the functional unit of the kidney responsible for its main functions?

The nephron is the functional unit of the kidney, and it plays a crucial role in the body's ability to filter blood, remove waste, and regulate fluid and electrolyte balance. Each kidney contains approximately one million nephrons, which consist of a renal corpuscle and a renal tubule.

The renal corpuscle filters blood to form a protein-free filtrate, and the renal tubule processes this filtrate, allowing for reabsorption of essential substances like water, glucose, and ions back into the bloodstream, while excreting waste products in the urine. This intricate system of filtration and reabsorption is vital for maintaining homeostasis in the body.

Other parts of the kidney, such as the calyx, cortex, and medulla, serve important structural and supportive functions but do not have the same role in the core processes of filtration and waste management that the nephron does. Therefore, understanding the nephron's significance is essential for grasping how the kidney functions overall.