nephros

Nephros is the ancient Greek word for the kidney. In modern medical language, the combining form nephro- derives from this term and appears in numerous terms describing kidney structure and function, such as nephron, nephritis, and nephrology.

In vertebrates, the kidney is a paired organ that filters blood to remove waste, regulates fluid and electrolyte balance, and maintains acid-base homeostasis. It also participates in hormone production, notably erythropoietin, activates vitamin D, and contributes to blood pressure regulation through the renin-angiotensin system. The organ is organized into an outer cortex and inner medulla, and contains millions of nephrons—the functional units responsible for filtration, reabsorption, and secretion that produce urine.

Anatomically, blood reaches a kidney via the renal artery, flows through a network of arterioles to glomeruli where filtration occurs, and the resulting filtrate travels through renal tubules. Along these tubules, essential substances are reabsorbed and wastes are secreted, adjusting the final urine composition before it drains into collecting ducts and the renal pelvis.

Developmentally, kidneys arise from the embryonic metanephros in mammals, after earlier pronephric and mesonephric stages. Nephrogenesis continues in some species after birth, while in others it completes prenatally.

Clinical relevance includes a broad spectrum of renal diseases such as nephritis (inflammation of the kidney), nephropathy (kidney disease), and nephrolithiasis (kidney stones). Evaluation commonly uses serum creatinine, estimated glomerular filtration rate, and urine analysis to assess kidney function and identify pathology.

The term nephros forms the basis of modern nephrology, the medical specialty dedicated to understanding and treating kidney function and disease.