glomerulares

Glomerulares are the functional units of the kidney responsible for the first step of blood filtration. In English, the standard term is glomeruli (plural), but glomerulares appears in some Latin-based texts. Each glomerulus is a compact tuft of capillaries embedded within Bowman's capsule at the start of a nephron.

Anatomy and structure: The glomerular tuft is lined by fenestrated capillary endothelium and is surrounded by a glomerular basement membrane. Podocytes, specialized epithelial cells with interdigitating foot processes, form filtration slits that contribute to the permeability barrier. The mesangial cells and matrix provide structural support and regulate surface area. Filtrate from the blood collects in Bowman's space before continuing into the renal tubule.

Filtration barrier and selectivity: The filtration barrier comprises three layers: the endothelial fenestrae, the basement membrane, and the slit diaphragms between podocyte foot processes. This design allows water and small solutes to pass while restricting plasma proteins and blood cells, helping to maintain plasma oncotic pressure and contribute to urine formation.

Physiology and regulation: Glomerular filtration rate (GFR) reflects the volume of filtrate produced per unit time and is tightly regulated. Autoregulation involves adjustments of afferent and efferent arteriolar tone, the tubuloglomerular feedback mechanism, and hormonal influences such as the renin–angiotensin system, which can alter filtration to preserve essential volumes and pressures.

Clinical relevance: Glomeruli are common sites of disease, including glomerulonephritis, diabetic nephropathy, and hypertensive kidney disease. Damage to the filtration barrier can cause proteinuria or hematuria and may lead to reduced kidney function. Evaluation relies on urinalysis, imaging, and, in some cases, renal biopsy to assess glomerular structure and pathology.