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RENAL CIRCULATION

RENAL CIRCULATION. S pecific learning objectives. Blood supply to the kidney Special features of renal circulation Measurement of renal blood flow. Blood supply of Kidney. Renal Blood vessels. Blood supply of Kidney. Special features.

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RENAL CIRCULATION

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  1. RENAL CIRCULATION

  2. Specific learning objectives • Blood supply to the kidney • Special features of renal circulation • Measurement of renal blood flow

  3. Blood supply of Kidney Renal Blood vessels

  4. Blood supply of Kidney

  5. Special features • Renal blood flow is about 1200 ml per minute(300ml/100gm) representing 25 per cent of cardiac output. • The arterio-venous difference in blood oxygen content is low in renal blood vessels (19ml% – 17.5ml%) • Oxygen consumption very high (6ml/100g/min)

  6. Special features • (A-V)O2 difference does not change in spite of alteration of blood flow. • Cortical blood flow is more than medulla • Portal system • High capillary hydrostatic pressure (45mmHg) • Three types of capillaries

  7. Measurement • Direct method • Electromagnetic flowmeter, Doppler method • Indirect method - Fick’s principle

  8. Measurement • Applying the Fick principle • Renal plasma flow can be measured by infusing para-aminohippuric acid (PAH) and determining its urine and plasma concentrations PAH clearance

  9. Measurement • Concentration of PAH in urine (UPAH): 14 mg/mL • Urine flow : 0.9 mL/min • Concentration of PAH in plasma (PPAH): 0.02 mg/mL •   =630 mL/min

  10. Autoregulation Blood flow is maintained at a constant level despite the change in the systemic pressure range between 80-180 mm Hg

  11. Features of Autoregulation • It is a characteristic feature of cortical and outer medullary renal blood flow • Renal autoregulation is present in denervated and in isolated, perfused kidneys • But is prevented by the administration of drugs that paralyze vascular smooth muscle. • Autoregulation is absent below 80 and above 180 mm Hg of renal perfusion pressure

  12. Autoregulation • Myogenic theory • Tubuloglomerular feedback mechanism • Metabolic mechanism – NO, prostagladins, adenosine • Neural regulation • Hormonal regulation

  13. Tubuloglomerular Feedback Stimulate Macula Densa (chemoreceptor)

  14. Summary

  15. References • Comprehensive Textbook of Medical physiology (Vol 2, 1stedition) G K Pal • Text book of medical physiology (Vol 2, 6thedition) A K Jain • Essentials of medical physiology (6thedition) K Sembulingam and PremaSembulingam

  16. Thank you

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