lect4. gfr.22.02.13

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reabsorption

Reabsorption = (GFR X Px ) – (Ux X Px)

Total filtration = con. of sub. in plasma x GFR

Ux XPx = con. Of sub. in urine x urine flow rate

= urinary excretory rate

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Dr. Ashok Solanki

Factors affecting G.F.R.

Changes in renal blood flow

Changes in glomerular capillary hydrostatic pressure

Changes in systemic blood pressure

Afferent or efferent arteriolar constriction

Changes in hydrostatic pressure in Bowman's capsule

Ureteral obstruction

Edema of kidney inside tight renal capsule

Changes in concentration of plasma proteins: dehydration, hypoproteinemia, etc (minor factors)

Changes in Kf

Changes in glomerular capillary permeability

Changes in effective filtration surface area

Tubular function

Reabsorption Secretion Concentration Acidification of tubular fluid

Filtered load = Px X GFR Px = concentration of the substance in

plasma GFR = is the glomerular filtration rate

per unit of time

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Inulin clearance

Cin = Uin x V/ PinInulin is a polysaccharide, molecular

weight – 5200, it is not produce in our body, found in root of certain plants, administered I.V to a patient to measure GFR

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Inulin clearance Cin = Uin x V/ PinInulin is a polysaccharide, molecular

weight – 5200, it is not produce in our body, found in root of certain plants, administered I.V to a patient to measure GFR

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Renal clearance

Definition – renal clearance of a substance is the volume of plasma that is completely cleared of the substance by the kidney per unit time

Inulin clearance is equal to GFR - highly filtered - neither reabsorb nor secreted - non toxic - should not metabolized - easy to measure plasma concentration - urine concentration can be measured

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Dr. Ashok Solanki

Forces promoting & opposesing filtration

Net filtration force is +ve causing filtration

Dr. Ashok Solanki

Junction- the JGA

Blood flows into the glomerulus throughthe afferent arterioles and leaves theglomerulus through the efferentarterioles. The proximal tubule exits Bowman’s capsule.

Dr. Ashok Solanki 1804.02.2013

Dr. Ashok Solanki

Dr. Ashok Solanki

Dr. Ashok Solanki

Juxtaglomerular Apparatus

1. granular cells differentiated smooth muscle cells of

afferent arterioles secretory vesicles contain renin2. extraglomerular mesangial cells continuous with the mesangium3. macula densa cells terminal part of thick ascending limb

LOH probably control both renin secretion

and GFR

Dr. Ashok Solanki

Dr. Ashok Solanki