Nefron

The nephron is the functional unit of the kidney, responsible for filtering blood, reabsorbing essential substances, and excreting waste as urine. Each human kidney contains approximately one million nephrons, arranged in a peripheral cortex and a central medulla. A typical nephron consists of a renal corpuscle, which includes the glomerulus—a tangled network of capillaries—and Bowman's capsule that encases it, and a tubular system comprised of the proximal convoluted tubule, the loop of Henle, the distal convoluted tubule, and the collecting duct.

Blood enters the glomerulus under pressure, allowing plasma water and small solutes to pass through the filtration membrane into Bowman's space, forming the glomerular filtrate. This filtrate then travels through the proximal tubule, where the majority of sodium, glucose, amino acids, and water are reabsorbed into the peritubular capillaries. The loop of Henle creates a concentration gradient in the renal medulla, enabling the kidney to produce urine of varying osmolarity. In the distal tubule, additional ion exchange and pH regulation occur under hormonal control, particularly by aldosterone and parathyroid hormone. Finally, the collecting duct adjusts water reabsorption in response to antidiuretic hormone, determining the final urine volume and concentration.

Nephron health is vital for overall renal function. Damage from hypertension, diabetes, or toxins can reduce nephron number, leading to impaired filtration and chronic kidney disease. Early detection and management of risk factors are essential to preserve nephron integrity and maintain fluid‑electrolyte balance.