GFR
Normal: 125 mL/min. Measured by inulin clearance (gold standard). Estimated by creatinine clearance or eGFR (CKD-EPI formula).
Creatinine clearance > GFR because of tubular secretion.
RAAS
Renin (JG cells) -> Angiotensinogen -> Angiotensin I -> ACE (lung) -> Angiotensin II -> Aldosterone (zona glomerulosa).
Effects: Vasoconstriction (angiotensin II), Na+ retention + K+ excretion (aldosterone), Thirst + ADH (angiotensin II).
Concentrating Mechanism
Countercurrent multiplier (Loop of Henle) + Countercurrent exchanger (vasa recta). ADH increases water reabsorption in collecting duct.
Revision history
- 20 September 2026 — Initial publication
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