What role does the nephron play in the kidney's function?

The nephron is the fundamental structural and functional unit of the kidney, playing a critical role in the process of urine formation. It facilitates this by performing three primary functions: filtration, reabsorption, and secretion. Initially, blood is filtered in the glomerulus portion of the nephron, allowing water, ions, and small molecules to pass while retaining larger molecules like proteins and blood cells. This filtered fluid, known as filtrate, then enters the renal tubule where reabsorption occurs. Essential substances and a significant amount of water are reabsorbed into the bloodstream at various segments of the nephron, including the proximal convoluted tubule, loop of Henle, and distal convoluted tubule.

Additionally, the nephron can secrete certain waste products and excess ions back into the filtrate, fine-tuning the composition of urine. Ultimately, the concentrated waste (urine) is collected in the collecting duct before it is transported to the bladder for excretion. This comprehensive role in the filtration and reabsorption processes makes the nephron essential for maintaining homeostasis, regulating water balance, electrolyte levels, and acid-base equilibrium in the body.