nephronsabout

Nephrons are the microscopic functional units of the kidney. Each nephron filters blood and forms urine while preserving essential water and solutes. In adults, about 85 percent are cortical nephrons with glomeruli in the outer cortex, and about 15 percent are juxtamedullary nephrons with longer loops extending toward the inner medulla. Nephrons regulate fluid balance, electrolyte levels, acid-base status, and waste excretion.

A nephron comprises a renal corpuscle and a renal tubule. The renal corpuscle contains a glomerulus connected to Bowman's capsule, where filtration begins. The renal tubule processes filtrate through the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct. Through reabsorption and secretion, tubules reclaim water, nutrients, and ions and add wastes to the filtrate.

Filtration at the glomerulus yields a glomerular filtration rate (GFR) around 90–120 mL/min in healthy adults. The filtration barrier includes the fenestrated capillary endothelium, glomerular basement membrane, and podocyte slit diaphragms. GFR is regulated by autoregulatory mechanisms—the myogenic response and tubuloglomerular feedback—as well as hormones such as angiotensin II, aldosterone, atrial natriuretic peptide, and antidiuretic hormone.

Nephrons develop during embryogenesis from the metanephric blastema; nephrogenesis largely completes before birth. Humans typically have about one million nephrons per kidney, though total number varies with genetics and prenatal factors. Loss or damage to nephrons reduces overall kidney function and can contribute to chronic kidney disease.