néphron

The néphron is the basic structural and functional unit of the kidney, responsible for producing urine. In humans, roughly one million nephrons populate each kidney. Each nephron consists of a renal corpuscle and a renal tubule. The renal corpuscle includes the glomerulus, a tuft of capillaries, and Bowman's capsule, which collects filtrate. The renal tubule comprises the proximal convoluted tubule, the loop of Henle (descending and ascending limbs), the distal convoluted tubule, and, in many nephrons, a collecting duct that receives filtrate from multiple nephrons.

Filtration occurs at the glomerulus, where plasma ultrafiltrate enters Bowman's space while blood cells and large proteins remain in the circulation. The tubule reabsorbs water and solutes and secretes waste products, shaping the final urine. The loop of Henle creates an osmotic gradient essential for concentrating urine, while the distal tubule and collecting duct adjust sodium, potassium, hydrogen, and bicarbonate levels under hormonal control.

Blood supply includes the afferent and efferent arterioles feeding the glomerulus; efferent flow creates the peritubular capillaries in the cortex or vasa recta in the medulla, enabling selective reabsorption and secretion. The juxtaglomerular apparatus regulates GFR through renin release.

Nephrons arise during kidney development from metanephric tissue interacting with the ureteric bud. Loss or damage to nephrons reduces GFR and can contribute to chronic kidney disease; nephron function can be impaired by diabetes, hypertension, and other diseases.