Glomérule

Glomérule, in anatomy, is the French term for the glomerulus, a tuft of capillaries at the vascular pole of each nephron in the kidney. It sits within Bowman's capsule and serves as the primary site of blood filtration, producing the filtrate that becomes urine after tubular processing. Blood enters through the afferent arteriole, passes through the capillary tuft with fenestrated endothelium, and exits via the efferent arteriole. The filtration barrier comprises the fenestrated endothelium, the glomerular basement membrane, and slit diaphragms formed by podocyte foot processes, with mesangial cells providing structural support.

Filtration is size- and charge-selective, allowing water and small solutes through while restricting larger proteins and cells. The glomérule can be classified by location as cortical or juxtamedullary; juxtamedullary glomeruli are typically situated near the corticomedullary junction and contribute to urine concentration.

Renal hemodynamics regulate GFR. Autoregulation includes the myogenic response of the afferent arteriole and tubuloglomerular feedback via the macula densa. The renin–angiotensin system can modulate filtration by altering arteriolar tone.

Clinical relevance: glomerular injury affects permeability and filtration, causing proteinuria, hematuria, or reduced GFR. Glomerular diseases (e.g., glomerulonephritis, diabetic nephropathy) damage the filtration barrier and may lead to chronic kidney disease. Diagnosis commonly uses urinalysis, imaging, and renal biopsy.

Development: glomeruli arise during nephron development from metanephric mesenchyme in response to signals from the ureteric bud.