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GFR(GLOMERULUAR) FILTRATION RATE AND IT`S REGULATIONPREPARED BY : SAIF ULLAH KHAN

REFRENCES: GUYTON(VALUES MECHANISMS)+K SEMBULINGAM+FIGURES GOOGLE

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LOCATION OF KIDNEY

ANATOMICAL LOCTAION•Kidneys are located in the abdominal cavity.•The asymmetry within the abdominal cavity•The right kidney being slightly lower and smaller than the left•The left kidney is approximately at the vertebral level T12 to L3

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INTRODUCTION TO KIDNEY

KIDNEY: We have 2 kidneys about the size of our fist. Each kidney contain about 1 million

filtrating functinal units called “Nephrons” Nephron contains a tiny filter called a

“Glomerulus“ Glomerulus are the structure like balls of

blood capillaries 2,millions of glomerulus filter about 3-4 liters of blood in 5mints.

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STRUCTURE OF KIDNEY

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STRUCTURE OF NEPHRON

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GLOMURULARFILTRATION RATE

DEFINITION:

The fluid that filters through the glomerulus into bowman`s capsule is called “glomerular filtration”.

NORMAL VALUE: 125ml/min

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GLOMERULAR FILTRAION

MEMBRANES THROUGH WHICH FILTRATION TAKES PLACE:

• The endothelial layer of the capillary(fenestrae).

• Basement membrane(it self is a meshwork)

• Layer of the epithelial cells bowman`s capsule.

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FIGURE

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MECHANISM

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IMPORTANT VALUES

FILTRATION COEFFICIENT (Kf):

The glomerular filtration rate in both kidneys per milli-meter of mercury of filtration pressure.

NORMAL VALUE: 12.5

ml/min/mmHg.

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GFR CALCULATIONS GFR CALCULATION: GFR= NET FILTRATION

PRESSURE . Kf

GFR = 10 mmHg . 12.5 ml/min/mmHg

GFR = 125ml/min.

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FILTRATION FRICTION RATE

FILTRATION FRICTION RATE: Amount of fluid

that filter through the bowman`s capsule membrane per mint.

NORMAL VALUE: 125ml/min

CALCULATON: F.F = GFR/R.P.F(renal plasma flow)

F.F = 125ml/min/600ml/min

F.F = 0.2 , 20%

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EFFECT OF BLOOD PRESSURE ON GFR

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REGULATION OF GFR ONCOTIC PRESSURE: The forces of

proteins molecules to attract water molecules because ,

• The proteins have charges• Acts as a polar substance• Like albumin There are two oncotic pressures one in glomerulus and

one in bowman`s capsule• Oncotic pressure is represented by I<(PIE)• Eg. I< Gc – I< BC

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REGULATION OF GFR 1.PLASMA ONCOTIC PRESSURE/ GLOMERULAR

ONCOTIC PRESSURE/ I<(pie)Gc:

• Force which keeps water in glomerulus

• Reverse force/pressure of filtration.

NORMAL VALUE: 28 mmHg.

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GREGULATION OF GFRONCOTIC PRESSURE IN BOWMANS

CAPSULE/ I< Bc:

• No proteins in bowman`s capsule

• But very low amount of amino acids.

• In healthy person no pressure is present

NORMAL VALUE: = 0(zero)

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REGULATION OF GFR HYDROSTATIC PRESSURE: Pressure of

fluid exerted on the wall of vessels/capillaries.

• We have two hydrostatic pressures one bowman`s capsule and one glomeruluar.

• Hydrostatic pressure is represented by = “P” • Eg PBc - PGc

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REGUKATION OF GFR

HYDROSTATIC PRESSURE IN THE GLOMERULAR CAPELLARIES: (Pgc)

• Fluid moving out from glomerular to bowman`s capsule.

• Promoting GFR

NORMAL VALUES: =45 mmHg

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REGULATION OF GFR

HYDROSTATIC PRESSURE IN THE BOWMAN`S SPACE / PBc:

• Fluid pressure which oppose the filtration.

• Its about 10mmHg

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REGULATION OF GFR

Finally the net filtration pressure• FORMULA:

NET FILTARION PRESSURE =

PGc - I<Gc - PBc *I<Bc=0 45 mmHg - 27mmHg -10mmHg =+8mmgh• Which proves that the fluid will move from

glomeruluar to bowman`s capsule.

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HORMONAL EFFECT ON GFR

NITRIC OXIDE: (local for kidney)• Its secreted by the smooth muscles

present in afferent arteriole which is activated by sensing the pressure in afferent arteriole

• Where as NO is a vasodilator• It will allow more fluid to flow into

the glomeruluar and more filtration will takes place.

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HORMONAL EFFRCT ON GFR• PROSTAGLANDINS:(PGE2)(PGI2)

(Major vasodilators) / local for kidney:• Released by the macula densa• Passed through the macula densa

mesangial cells J.G cells vasodilatation

• BRADYKININ:• vasodilators• Out side from the kidney SYMPHETATIC CELLS (beta receptors)• Causes vasodilatation.

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APPLIED PHYSIOLOHY OF GFR

WILL BE DISCUSSED ON

BOARD