What functional units of the kidneys are responsible for urine formation?

Nephrons are the functional units of the kidneys that are directly responsible for urine formation. Each nephron consists of a renal corpuscle, which includes the glomerulus, and a renal tubule. The nephron's primary functions include filtering blood, reabsorbing necessary substances, and secreting waste products into the tubular fluid, which ultimately leads to urine formation.

Within the nephron, the glomerulus plays a crucial role by acting as a filtration unit, but it is part of the larger nephron structure. The renal tubules are involved in important processes such as reabsorption and secretion, but they operate within the framework of the nephron itself. The renal pelvis is not involved in urine formation; rather, it serves as a channel for urine to exit the kidney into the ureter. Therefore, while other components such as glomeruli and tubules contribute to urine formation, it is the nephron as a whole that encompasses all these functions and is designated as the functional unit of the kidney.