PY7.1-9 | Renal Physiology — Glossary

Volume of filtrate formed per minute across all glomeruli; normal ~125 mL/min (180 L/day); the primary measure of kidney function.

The fraction of renal plasma flow that is filtered at the glomerulus; normally ~20% (GFR/RPF = 125/660).

The functional unit of the kidney comprising the glomerulus, Bowman's capsule, PCT, loop of Henle, DCT, and collecting duct.

Specialised epithelial cell wrapping around glomerular capillaries; foot processes form the slit diaphragm (final filtration barrier) containing nephrin protein.

Negatively charged meshwork between endothelium and podocytes that repels albumin; damaged by glycation in diabetic nephropathy.

Hydrostatic and oncotic pressures that determine the net filtration pressure driving glomerular filtration.

Specialised structure at the vascular pole of the glomerulus comprising macula densa, JG cells, and extraglomerular mesangial cells; controls GFR and renin release.

Specialised cells of the DCT adjacent to the afferent arteriole that sense NaCl concentration in tubular fluid and regulate GFR via tubuloglomerular feedback.

Enzyme released by juxtaglomerular cells in response to low BP, low Na+ at macula densa, or sympathetic stimulation; initiates the RAAS cascade.

Sodium-glucose co-transporter 2 in the PCT responsible for reabsorbing ~90% of filtered glucose; target of gliflozin drugs in Type 2 diabetes.

The maximum rate at which a substance can be reabsorbed or secreted by the tubules when all carriers are saturated; Tm for glucose is ~375 mg/min.

Mechanism in the loop of Henle that creates the medullary osmotic gradient (300-1200 mOsm/L) by the single effect multiplied through counter-current flow.

The vasa recta, which run parallel to the loop of Henle and preserve the medullary gradient by equilibrating with the interstitium without washing it out.

Water channel inserted into the apical membrane of collecting duct principal cells in response to ADH; allows water reabsorption for urine concentration.

Posterior pituitary hormone that acts on V2 receptors in collecting duct to insert aquaporin-2; deficiency causes diabetes insipidus.

Mineralocorticoid from the adrenal zona glomerulosa that acts on collecting duct to increase ENaC expression (Na+ reabsorption) and K+ secretion.

Volume of plasma completely cleared of a substance per unit time; C = (U x V) / P; inulin clearance equals GFR.

Endogenous waste product of muscle metabolism; freely filtered and slightly secreted; serum level and clearance used clinically to estimate GFR.

Hydrogen ions buffered by urinary phosphate (HPO42- → H2PO4-) representing one mechanism of renal acid excretion and new bicarbonate generation.

Major renal mechanism for acid excretion: glutamine metabolised to NH4+ in PCT, trapped in acidic urine; upregulated in chronic acidosis.

Smooth muscle of the bladder wall that contracts during voiding under parasympathetic (M3 muscarinic receptor) control.

Coordinated voiding reflex: bladder stretch → sacral centre (S2-S4) → parasympathetic activation → detrusor contraction + sphincter relaxation, modulated by pontine centre.

Extracorporeal blood purification using diffusion and ultrafiltration across a synthetic membrane; performed 3-4 times weekly for end-stage kidney disease.

Dialysis using the peritoneal membrane as a biological filter; dialysate instilled into the peritoneal cavity for solute and water exchange.

Loop diuretic that blocks the NKCC2 co-transporter in the thick ascending limb; the most potent diuretic class; used in pulmonary oedema and heart failure.