L3 Glomerular filtration rate (P1 Mid)
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Questions and Answers

What is the glomerular filtration rate (GFR)?

  • 125 ml/min (correct)
  • 180 ml/min
  • 250 ml/min
  • 75 ml/min

What percentage of renal plasma flow (RPF) is represented by the GFR?

  • 20% (correct)
  • 50%
  • 10%
  • 30%

What is the filtration fraction in the kidneys?

  • 30%
  • 10%
  • 5%
  • 20% (correct)

What is the rate at which fluid enters the glomerulus and is filtered?

<p>125 ml/min (C)</p> Signup and view all the answers

What type of cells form the inner layer of the Bowman’s capsule?

<p>Podocytes (D)</p> Signup and view all the answers

Which of the following processes is NOT part of urine formation?

<p>Hepatic detoxification (D)</p> Signup and view all the answers

What happens to the 80% of plasma that enters the glomerulus?

<p>It leaves through the efferent arteriole (C)</p> Signup and view all the answers

Which component of the glomerular filtration barrier provides structural support?

<p>Collagen (D)</p> Signup and view all the answers

How does filtered fluid pass through the glomerular membrane?

<p>Extracellularly through two membranes (D)</p> Signup and view all the answers

What characteristic makes the capillary endothelium in the glomerulus unique compared to other capillaries?

<p>It is 100 times more permeable (B)</p> Signup and view all the answers

What happens to the Glomerular Filtration Rate (GFR) when the arterial blood pressure (ABP) is maintained within the range of 75-160 mmHg?

<p>GFR remains unaffected due to autoregulation. (C)</p> Signup and view all the answers

How does an increase in glomerular colloid osmotic pressure affect the GFR?

<p>It decreases the GFR. (C)</p> Signup and view all the answers

What effect does an increase in hydrostatic pressure in Bowman's capsule have on the GFR?

<p>It decreases the GFR. (B)</p> Signup and view all the answers

Which factor directly contributes to an increase in GFR?

<p>High glomerular capillary permeability. (B)</p> Signup and view all the answers

What is the effect of severe sympathetic stimulation on renal blood flow (RBF) and GFR?

<p>It decreases both RBF and GFR. (A)</p> Signup and view all the answers

How does increasing the diameter of the afferent arteriole affect GFR?

<p>It increases capillary pressure and GFR. (D)</p> Signup and view all the answers

What effect does a high protein intake have on renal function?

<p>It increases renal blood flow and GFR. (A)</p> Signup and view all the answers

What happens to GFR when the number of functioning nephrons is decreased?

<p>GFR decreases significantly. (D)</p> Signup and view all the answers

What is the formula for calculating inulin clearance?

<p>C = U * V / P (B)</p> Signup and view all the answers

What is considered a normal value for glomerular filtration rate (GFR)?

<p>125 ml/min (A)</p> Signup and view all the answers

Which substance will have a clearance value less than that of inulin?

<p>Urea (A)</p> Signup and view all the answers

If a substance is completely reabsorbed, what will its clearance value be?

<p>Zero (D)</p> Signup and view all the answers

What happens to a substance that is secreted from the renal tubules?

<p>Its clearance value is higher than inulin clearance (B)</p> Signup and view all the answers

Which pressure is NOT part of the filtration force in the glomerulus?

<p>Blood pressure (A)</p> Signup and view all the answers

What is the key importance of measuring inulin clearance?

<p>It indicates glomerular health (C)</p> Signup and view all the answers

Which of the following statements about glomerular filtration is true?

<p>It is the first step in the formation of urine. (A)</p> Signup and view all the answers

What is the function of the filtration slits between podocyte foot processes?

<p>They allow selective filtration of small molecules. (A)</p> Signup and view all the answers

Which force acts as a reabsorbing force in the glomerulus?

<p>Plasma colloid osmotic pressure (C)</p> Signup and view all the answers

What is the net filtration pressure calculated in the glomerulus?

<p>10 mmHg (D)</p> Signup and view all the answers

What is the typical diameter range for substances that can freely pass through glomerular capillaries?

<p>Between 4 nm to 8 nm (C)</p> Signup and view all the answers

What is the primary composition of the basement membrane in glomerular capillaries?

<p>Collagen and glycoprotein (A)</p> Signup and view all the answers

What effect does an increase in renal blood flow have on the glomerular filtration rate (GFR)?

<p>It increases GFR. (A)</p> Signup and view all the answers

Which of the following statements is true about glomerular capillary hydrostatic pressure?

<p>It drives the filtration process. (C)</p> Signup and view all the answers

What size of particles cannot pass through the filtration barriers in the glomerulus?

<p>Greater than 8 nm (D)</p> Signup and view all the answers

What type of arteriole is larger in diameter relative to its counterpart in the glomerulus?

<p>Afferent arteriole (C)</p> Signup and view all the answers

Which of the following characterizes glomerular capillaries?

<p>High permeability (C)</p> Signup and view all the answers

Flashcards

Glomerular Filtration Rate (GFR)

The volume of blood filtered by both kidneys per minute.

Filtration Fraction

The percentage of plasma that is filtered by the glomerulus.

Glomerular Filtration

The process by which blood plasma is filtered in the glomerulus.

Renal Plasma Flow (RPF)

The amount of plasma that flows through the kidneys per minute.

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Afferent and Efferent Arterioles

The tiny blood vessels that supply the glomerulus.

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Glomerulus

A tiny ball of capillaries within the nephron, responsible for filtering blood.

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Bowman's Capsule

A layer of tissue surrounding the glomerulus, composed of podocytes that help filter blood.

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Podocytes

Specialized cells lining the Bowman's capsule, with octopus-like foot processes that wrap around the glomerular tuft.

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Basement Membrane

A thin layer separating the glomerular capillary and the Bowman's capsule, composed of collagen and negatively charged glycoproteins.

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Filtration Slits

Filtration slits, formed between the foot processes of podocytes, are the gaps where fluid filters from the glomerular capillaries into Bowman's capsule.

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Endothelium of Glomerular Capillaries

The endothelium is the inner lining of the glomerular capillaries, with pores that allow small molecules to pass through.

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Glomerular Capillary Hydrostatic Pressure

The glomerular capillary hydrostatic pressure is the force that pushes fluid from the blood into Bowman's capsule.

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Plasma Colloid Osmotic Pressure

The plasma colloid osmotic pressure is the force that draws fluid back into the capillaries.

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Bowman's Capsule Hydrostatic Pressure

The Bowman's capsule hydrostatic pressure is the force that opposes fluid movement into Bowman's capsule.

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How does mean arterial blood pressure affect GFR?

Within a range of 75-160 mmHg, mean arterial blood pressure (ABP) does not affect GFR due to autoregulation. Beyond this range, GFR is directly proportional to ABP.

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How does glomerular colloid osmotic pressure affect GFR?

Increased colloid osmotic pressure (COP) reduces GFR, while decreased COP increases GFR. Dehydration is an example of increased COP.

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How does hydrostatic pressure in Bowman's capsule affect GFR?

Increased hydrostatic pressure in Bowman's capsule reduces GFR. This can occur due to conditions like ureteric stones.

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How does glomerular capillary permeability affect GFR?

GFR is directly proportional to the glomerular capillary permeability. Increased permeability allows more fluid to filter through.

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How does sympathetic stimulation affect GFR?

Severe sympathetic stimulation causes vasoconstriction, reducing renal blood flow (RBF) and GFR.

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How does afferent arteriole diameter affect GFR?

Increased diameter of the afferent arteriole reduces resistance, increasing blood flow and glomerular capillary pressure, ultimately leading to increased GFR.

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How does efferent arteriole diameter affect GFR?

Mild vasoconstriction of the efferent arteriole increases resistance, increasing glomerular capillary pressure and GFR. However, severe vasoconstriction initially increases GFR but ultimately leads to a marked decrease.

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What makes inulin a good marker for GFR?

Inulin is freely filtered by the glomerulus and neither reabsorbed nor secreted by the renal tubules, making its clearance rate equal to the GFR.

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What is the normal glomerular filtration rate?

The normal glomerular filtration rate is approximately 125 ml/min, meaning that this volume of blood plasma is filtered by both kidneys every minute.

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What factors influence GFR?

The glomerular filtration rate (GFR) is influenced by factors like blood pressure, renal blood flow, and the permeability of the glomerular capillaries.

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What is the filtration force in the glomerulus?

The filtration force in the glomerulus is the difference between the hydrostatic pressure in the glomerular capillaries and the combined pressure from the colloid osmotic pressure of the plasma and the hydrostatic pressure in Bowman's capsule.

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What happens to the clearance value of a substance that's completely reabsorbed?

If a substance is completely reabsorbed in the renal tubules, its clearance value will be zero. This is because none of the substance ends up in the urine.

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What happens to the clearance value of a substance that's secreted?

If a substance is secreted from the renal tubules, its clearance value will be higher than inulin clearance. This is because more of the substance appears in the urine than was originally filtered.

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What is glomerular filtration and its product?

Glomerular filtration is the first step in the formation of urine, where blood plasma is filtered through the glomerular capillaries into Bowman's capsule. This filtrate is known as primary urine.

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How does a high protein diet affect GFR?

A high protein diet can increase glomerular filtration rate (GFR). This is because the increased protein load in the blood increases the colloid osmotic pressure in the blood, which in turn increases the filtration pressure in the glomerulus.

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Study Notes

Renal Module - Course Information

  • Course code: IMP-07-20318
  • Phase: I
  • Year/semester: 2nd year/Semester 3
  • Credit hours: [Not specified]
  • Course duration: 5 weeks

Lecture 3: Physiology of Glomerular Filtration Rate (GFR) and Affecting Factors

  • Intended Learning Outcomes (ILOs):
    • Define glomerular filtration rate (GFR) and identify its value.
    • List factors affecting GFR.
    • Describe the method of GFR measurement.

Glomerular Filtration

  • Glomerular filtration is a passive process (ultrafiltration).
  • GFR is the volume of fluid filtered by both kidneys per minute.
  • GFR = 125 ml/min
  • GFR accounts for 20% of renal plasma flow (RPF). RPF = 625ml/min

Filtration Fraction

  • Filtration fraction is the fraction of plasma filtered by the glomeruli.
  • Filtration fraction = GFR / RPF = 125 ml/min / 625 ml/min = 20%

Three Basic Processes in Urine Formation

  • Glomerular Filtration (GF): Initial step in urine formation
  • Tubular Reabsorption (TR): Process of reabsorbing useful substances back into the blood
  • Tubular Secretion (TS): Secretion of substances from the blood into the tubules

Structure of Glomerular Filtration Membrane

  • The membrane has three layers:
    • Capillary endothelium: Permeable to water and small solutes
    • Basement membrane: Formed of collagen and glycoprotein; negatively charged, and restricts filtration
    • Podocytes: Have foot processes that form filtration slits, which further restricts filtration of larger molecules

Forces Acting on Glomerular Filtration

  • Glomerular capillary hydrostatic pressure (GCPH): Pushes fluid into Bowman's capsule. ≈ 55 mmHg
  • Plasma colloid osmotic pressure (PCOP): Draws fluid back into the capillaries. ≈ 30 mmHg
  • Bowman's capsule hydrostatic pressure (BCPH): Pushes fluid out of Bowman's capsule. ≈ 15 mmHg
  • Net filtration pressure (NFP): The difference between the forces that favor filtration and forces that oppose it. NFP= GCPH – (PCOP+BCPH) = 10 mmHg

Regulation of GFR

  • Renal blood flow (RBF): Directly proportional to GFR
  • Arterial blood pressure (ABP): Within a range of 75-160 mmHg, GFR is stable due to autoregulation. Outside of this range, GFR is directly proportional to ABP
  • Afferent arteriole diameter: Dilatation increases blood flow, capillary pressure, and GFR. Constriction decreases blood flow, capillary pressure, and GFR.
  • Efferent arteriole diameter: Mild constriction increases glomerular capillary pressure and GFR; severe constriction initially increases GFR, then causes a decrease.
  • Glomerular colloid osmotic pressure: Increased colloid osmotic pressure decreases GFR
  • Bowman's capsule hydrostatic pressure: Increased hydrostatic pressure decreases GFR
  • Glomerular capillary permeability: Permeability is directly proportional to GFR
  • Sympathetic stimulation: Marked sympathetic stimulation decreases RBF and GFR

Measurement of GFR

  • Inulin clearance: Inulin is a substance that is freely filtered, neither reabsorbed nor secreted by the tubules. GFR is measured by inulin clearance and equals 125 ml/min

Importance of Inulin Clearance

  • Reference value: Used to assess GFR as it precisely reflects the clearance of substances freely filtered from the plasma
  • Reabsorbed substances: Clearance value of substances reabsorbed by the tubules is less than inulin's
  • Completely reabsorbed substances: Have a clearance value of zero (e.g., glucose).
  • Secreted substances: Clearance is higher than inulin's

Additional Notes

  • Glomerular filtration: The first step in urine formation, involving the filtration of plasma through the glomerulus.
  • GFR: The rate at which fluid is filtered by the glomeruli.
  • RBF: Renal blood flow.
  • ABP: Arterial blood pressure.

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L3 Glomerular Filtration Rate PDF - Renal Module

Description

Test your knowledge on kidney physiology and the glomerular filtration rate (GFR) with this quiz. Understand key concepts such as renal plasma flow, filtration fraction, and the functions of different cells in the kidney. Dive into the fascinating world of urine formation and filtration processes.

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