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The Renal System

Renal Blood Flow. The Renal System. Objectives. Describe the renal blood flow Describe the control of the renal blood flow. Renal Blood Flow. The renal blood flow = 1.2 L/min 25% of the cardiac output 90% perfuse cortex, 10% perfuse medulla. Functions of Renal Blood Flow.

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The Renal System

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  1. Renal Blood Flow The Renal System Lecture 2 Dr. Amal Mahmoud Saeed

  2. Objectives Describe the renal blood flow Describe the control of the renal blood flow

  3. Renal Blood Flow The renal blood flow = 1.2 L/min 25% of the cardiac output 90% perfuse cortex, 10% perfuse medulla. Lecture 2 Dr. Amal Mahmoud Saeed

  4. Functions of Renal Blood Flow Delivers oxygen , nutrient and hormones to cells of the nephron and return carbon dioxide and reabsorbed fluids and solutes to the circulation Indirectly determining the glomerular filtration rate Modifies the rate of solute and water re-absorbed in proximal tubules Participates in the concentration and dilution of urine Delivers substrates for secretion in urine Lecture 2 Dr. Amal Mahmoud Saeed

  5. Regulation of Renal Blood Flow (RBF) • Auto-regulation • Neural regulation • Hormonal regulation Lecture 2 Dr. Amal Mahmoud Saeed

  6. Regulation of Renal Blood Flow (RBF) • Auto-regulation Is defined as the ability of the kidney to maintain blood flow during changes in perfusion pressure. Lecture 2 Dr. Amal Mahmoud Saeed

  7. Regulation of Renal Blood Flow (RBF) • Renal blood flow is expressed by the following formula: Q= ΔP • Q flow • ΔP Pressure gradient • R Resistance R • To maintain flow Q constant while changing pressure ΔP, R must change. • This change in resistance is mainly by alteration in arteriolar diameter, specially the afferent arteriole. Lecture 2 Dr. Amal Mahmoud Saeed

  8. Regulation of Renal Blood Flow (RBF) • The kidney auto-regulates in the perfusion pressure range of 80-180mmHg Lecture 2 Dr. Amal Mahmoud Saeed

  9. Regulation of Renal Blood Flow (RBF) • Auto- regulation depends on two mechanisms: • myogenic response: vascular smooth muscles contract when stretched by increasing pressure. Lecture 2 Dr. Amal Mahmoud Saeed

  10. Regulation of Renal Blood Flow (RBF) • tubulo -glomerular feed back: the macula densa detects changes in perfusion pressure by detecting changes in tubular flow. A vaso-active substance is released which changes vascular resistance accordingly. Lecture 2 Dr. Amal Mahmoud Saeed

  11. Regulation of Renal Blood Flow (RBF) • Neural Regulation Renal sympathetic nerve stimulation increases renal vascular resistance of both afferent and efferent arterioles this decreases renal blood flow. Lecture 2 Dr. Amal Mahmoud Saeed

  12. Regulation of Renal Blood Flow (RBF) • Hormonal Regulation - angiotensin II constricts both afferent and efferent arterioles and reduces renal blood flow. - Prostaglandins are produced within the kidney PGE1 and PGI2 are vasodilators and thromboxane A2 is a vasoconstrictor. Lecture 2 Dr. Amal Mahmoud Saeed

  13. Summary Renal blood flow is about 1.2L/min Regulated by auto regulation, neural and hormonal mechanisms

  14. Functions of the Kidney Lecture 2 Dr. Amal Mahmoud Saeed

  15. Functions of the Kidney • Excretion of waste products • Regulation of the concentration of electrolytes in E.C.F. • Regulation of the osmolality of E.C.F. Lecture 2 Dr. Amal Mahmoud Saeed

  16. Functions of the Kidney • Regulation of the volume of E.C.F • Regulation of the pH. of E.C.F. • Regulation of blood pressure Lecture 2 Dr. Amal Mahmoud Saeed

  17. Functions of the Kidney • Endocrine functions • erythropoietin • 1-25 dihydroxy cholecalciferol • renin • prostaglandins Lecture 2 Dr. Amal Mahmoud Saeed

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