Download MBBS Physiology Presentations 3 Renal Gfr And Rbf Lecture Notes

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To understand the function of the filtration membrane

To define glomerular filtration rate, renal blood flow

To measure glomerular filtration rate, renal blood flow

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Basic Processes required for Formation of Urine

1. Glomerular filtration-

2. Tubular processing-

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a. reabsorption &

b. secretion)

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3. Urinary excretion-

.

Site of filtration - Glomerulus

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Physiology of Glomerular filtration

Glomerular filtrate
Glomerular ultrafiltrate-protein & cel ular elements free blood

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Important contributors:

1. Filtration Membrane (Barrier)

2. Unique pressure dynamics

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within the glomeruli

https://www.researchgate.net/publication/285735121_Regulation_of_renal_hemodynamics/figures?lo=1

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Glomerular Filtration Membrane / Barrier

1) Endothelial cells layer of the capil ary,

2) Basement membrane and

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3) Epithelial cells (podocytes) ? surrounding outer surface of cp

basement membrane.
Glomerular Filtration Barrier ? Cp Endothelial layer

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The capillary endothelium has thousands of small holes called

fenestrae

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But loaded with negative charged glycoproteins

Glomerular Filtration Barrier - basement membrane

The surrounding basement membrane - is a porous meshwork of

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proteins ? contain type IV collagen and proteoglycan fibrillae.
Glomerular Filtration Barrier ? Podocytes Layer

The long finger like processes of the podocytes interdigitate to

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cover the basement membrane and are separated by apparent

gaps called filtration slits.

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Glomerular Filtration Barrier ? Podocytes Layer
GFB restricts the filtration of substances on the basis of

Size & Electrical charges

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Applied - Kidney diseases (Nephropathies) and

Filtration Barrier

Nephrotic syndrome

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Glomerulonephritis

Hypertension
2.Unique pressure dynamics within the glomeruli

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Dia of afferent arteriole > efferent glom arteriole ?

Capil ary bed between two arteries?

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Glomerular Filtration Rate
Glomerular Filtration Rate

120 ml/min

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Renal Blood Flow

RBF

1100 ml/min,

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RBF is important as -
Renal Clearance/ Renal plasma clearance

10 L

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This much volume of fluid

is free of drug in unit time.

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Relative clearances of substances
Estimation of GFR by

Renal Plasma Clearance

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GFR:

Substance: Inulin

Estimation of RBF by

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Renal Plasma Clearance

RBF:

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Substance: PAHA
Estimation of GFR? Renal Plasma Clearance

GFR

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(C )=U X V / P

in

in

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in

Estimation of GFR and RBF ? Renal Plasma Clearance

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RBF:
RBF =RPF/0.9 (1-hematocrit)
Estimation of GFR and RBF ? Renal Plasma Clearance

Clinical problem ? TO calculate GFR :

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Estimation of GFR and RBF ? Renal Plasma Clearance

Problem-RBF: Calculate RBF of a patient
Filtration Fraction

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Filtration Fraction = GFR/RPF=125/625=0.20

20%

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Filtration Fraction

Increase in the filtration fraction -

Decrease in the filtration fraction -

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Applied Physiology

Glomerular filtration rate (GFR) is an important clinical indicator

of status of kidney function.

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Applied Physiology

Serum Creatinine:

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normal value =
Significant points in lecture

Filtration barrier, Slit diaphragm, disorder in nephrotic syndrome

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Uniqueness of pressure dynamics in glomeruli

GFR, RBF

Substances of measurement and clearance

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MCQ

renal clearance of a substance is the VOLUME OF PLASMA from which that
substance is completely removed (cleared) per unit time.Inn that case following is

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a false statement:

a) Renal clearance = GFR when No net reabsorption, secretion
b) Renal clearance = GFR when No net reabsorption

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c) Renal clearance > GFR Net secretion

d) Renal clearance < GFR Net reabsorption

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If a normal person has a plasma creatinine level 1 mg/dl that later

becomes 2 mg/dl, what happens to GFR?

Ans: 50% of the value of GFR at1 mg/dl.

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