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gfr and its regulation.pptx
- 1. BY:- RITIK BANSAL ROLLNO. - 115
- 2. Overview • DEFINITION • MECHANISMOF GLOMERULAR FILTRATION • MEASUREMENT OF GFR • FACTOR AFFECTING GFR • REGULATION OF GFR
- 3. DEFINITION:- • Glomerular filtrationrate is defined as the amount of filtrate formed by glomerular filtering membrane of both the kidneys in a unit time. MECHANISM OF GLOMERULAR FILTRATION Glomerular filtration occur through the glomerulocapsular filtration barrier that consist of fenestrated capillary endothelium, the basement membrane, and podocytes of capsular epithelium.
- 4. • GFR isdetermined by 1. The sum of Hydrostatic pressure and colloid osmotic pressure across the glomerular membrane, which give net filteration pressure. 2. Glomerular capillary filtration coefficient (Kf). GFR = Kf × Net filtration pressure GFR = Kf × (Pc – PB − ∏c + ∏B )
- 5. Filtration Coefficient • Itis the product of glomerular capillary wall permeability and the effective filtration surface area(size of the capillary bed). It cannot be measured directly, but it is measured experimentally by dividing the rate of glomerural filtration by net filtration pressure. Kf = GFR / Net filtration pressure * Increase Kf raises GFR and decrease Kf reduces GFR
- 6. Measurement Of GFR InulinClearance Test:- It is measured by measuring the concentration of the inulin in urine and the plasma concentration of inulin . GFR =
- 7. Effect of Arterioleresistance on GFR
- 8. Factors Affecting GFR 1.Change in renal blood flow 2. Glomerular capillary hydrostatic pressure 3. Change in capsular hydrostatic pressure 4. Oncotic pressure 5. Glomerular capillary permeability 6. Effective filtration surface area 7. Shape, size, and electrical charge of the macromolecule. Filtration Fraction:- It is the ratio of the GFR to renal plasma flow. It ranges between 0.16 to 0.20
- 9. REGULATION OF GFR •Neural Mechanism • Hormonal Mechanism • AutoRegulatory Mechanism Neural Mechanism:- Both afferent and efferent arterioles are innervated by sympathetic fibers. Activation of sympathetic fibers cause constriction of the renal arteriole and cause decrease in renal blood flow hence, decrease in GFR. The renal sympathetic nerves seems to be more important in reducing GFR during severe, acute disturbances for a few minutes to a few hours, such as brain ischemia, or severe hemorrhage.
- 10. Autoregulatory Mechanism The autoregulationof GFR maintain a constant rate of glomerular filtration despite change in systemic arterial pressure within the range of 80-180 mm Hg . This is mainly due to the Myogenic theory and Theory of tubuloglomerular feedback.
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