Count to 10 - Anaesthetic Primary Podcast EP46 – Counter-Current Mechanism, Urine Production and Applied physiology | Anaesthetic Primary Topic | Renal Physiology | CT10
Dec 16, 2025
Dive into the fascinating world of renal physiology! Discover the counter-current mechanism's role in urine concentration and dilution. Learn how the RAAS regulates kidney function and the significance of ADH in managing water reabsorption. Explore the differences between acute and chronic renal conditions, alongside clinical assessments. Plus, uncover the effects of atrial natriuretic peptide on renal blood flow. It's a deep yet enjoyable journey through how our kidneys maintain balance!
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Loop Of Henle As A Multiplier
- The loop of Henle multiplies small osmotic differences to create a very large medullary gradient.
- Repeated selective water and solute flux raises interstitial osmolality to ~1200–1400 mOsm/kg.
Vasa Recta Preserves Gradient
- The vasa recta preserves the medullary gradient by counter-current exchange and slow flow.
- It passively picks up solutes and returns water so net plasma osmolality changes little (~300→320 mOsm/kg).
Urea Boosts Medullary Osmolality
- Urea contributes about half of medullary interstitial osmolality and is modulated by ADH.
- ADH increases urea permeability in medullary collecting ducts, enhancing the concentrating gradient.