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Questions and Answers
What is the primary purpose of the glomerulus in renal circulation?
What is the primary purpose of the glomerulus in renal circulation?
Which component of renal circulation receives blood directly from the afferent arteriole?
Which component of renal circulation receives blood directly from the afferent arteriole?
What percentage of cardiac output is typically supplied to the kidneys?
What percentage of cardiac output is typically supplied to the kidneys?
How is renal plasma flow calculated in the context of kidney function?
How is renal plasma flow calculated in the context of kidney function?
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What is renal plasma flow expressed as a percentage of renal blood flow?
What is renal plasma flow expressed as a percentage of renal blood flow?
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What is the primary site of reabsorption in the renal circulation?
What is the primary site of reabsorption in the renal circulation?
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What is the definition of plasma clearance in renal function?
What is the definition of plasma clearance in renal function?
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Which of the following accurately describes renal circulation?
Which of the following accurately describes renal circulation?
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What percentage of PAHA in arterial plasma is typically excreted in urine?
What percentage of PAHA in arterial plasma is typically excreted in urine?
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Which formula correctly represents the relationship between effective renal plasma flow (ERPF) and actual renal plasma flow (RPF)?
Which formula correctly represents the relationship between effective renal plasma flow (ERPF) and actual renal plasma flow (RPF)?
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What percentage of plasma entering the glomerulus typically gets filtered?
What percentage of plasma entering the glomerulus typically gets filtered?
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Which process is NOT one of the three basic renal processes mentioned?
Which process is NOT one of the three basic renal processes mentioned?
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In response to increased arterial blood pressure (ABP), what happens to the diameter of the afferent arteriole?
In response to increased arterial blood pressure (ABP), what happens to the diameter of the afferent arteriole?
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What is the glomerular filtration rate (GFR) when 625 ml/min of plasma enters the glomerulus?
What is the glomerular filtration rate (GFR) when 625 ml/min of plasma enters the glomerulus?
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Which component of renal physiology is primarily involved in raising capillary pressure to increase GFR?
Which component of renal physiology is primarily involved in raising capillary pressure to increase GFR?
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What does the term 'tubular reabsorption' refer to in kidney function?
What does the term 'tubular reabsorption' refer to in kidney function?
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What is the primary aim of extrinsic control in kidney function?
What is the primary aim of extrinsic control in kidney function?
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Which structure detects changes in arterial blood pressure for extrinsic regulation?
Which structure detects changes in arterial blood pressure for extrinsic regulation?
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What role does sympathetic nervous stimulation play in extrinsic control?
What role does sympathetic nervous stimulation play in extrinsic control?
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How does extrinsic control impact glomerular filtration rate (GFR)?
How does extrinsic control impact glomerular filtration rate (GFR)?
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What is the result of long-term adjustments to arterial blood pressure?
What is the result of long-term adjustments to arterial blood pressure?
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Which of the following describes a component of intrinsic regulation in renal blood flow?
Which of the following describes a component of intrinsic regulation in renal blood flow?
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What effect does generalized vasoconstriction have on renal physiology?
What effect does generalized vasoconstriction have on renal physiology?
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What is meant by the term 'clearance of a substance' in kidney function?
What is meant by the term 'clearance of a substance' in kidney function?
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What is the primary aim of kidney autoregulation?
What is the primary aim of kidney autoregulation?
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Which mechanism is NOT part of kidney autoregulation?
Which mechanism is NOT part of kidney autoregulation?
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How does the myogenic mechanism respond to increased arterial blood pressure?
How does the myogenic mechanism respond to increased arterial blood pressure?
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What occurs when the afferent arteriole is constricted during autoregulation?
What occurs when the afferent arteriole is constricted during autoregulation?
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What triggers the tubuloglomerular feedback mechanism?
What triggers the tubuloglomerular feedback mechanism?
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Which arterial blood pressure range allows for optimal autoregulation of GFR?
Which arterial blood pressure range allows for optimal autoregulation of GFR?
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What would be the consequence if arterial blood pressure falls below the autoregulation range?
What would be the consequence if arterial blood pressure falls below the autoregulation range?
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What is the effect of the vasoactive chemicals released by the macula densa cells?
What is the effect of the vasoactive chemicals released by the macula densa cells?
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During autoregulation, what does an increase in blood flow into the glomerulus cause?
During autoregulation, what does an increase in blood flow into the glomerulus cause?
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Which part of the kidney anatomically interacts with the juxtaglomerular apparatus to facilitate tubuloglomerular feedback?
Which part of the kidney anatomically interacts with the juxtaglomerular apparatus to facilitate tubuloglomerular feedback?
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Study Notes
Renal Module Information
- Course code: IMP-07- 20318
- Phase: I
- Year/semester: 2nd year / Semester 3
- Academic year: 2022-2023
Lecture 2: Renal Circulation and Autoregulation of Renal Blood Flow
- Lecturer: Prof. Dr. Aziza Khalil
- Topic: Renal circulation and its significance, regulation of renal blood flow, plasma clearance and its measurement
Intended Learning Outcomes (ILOs)
- Students will be able to describe renal circulation and its significance.
- Students will be able to discuss the regulation of renal blood flow.
- Students will be able to identify plasma clearance and its measurement.
Renal Circulation
- Renal artery → interlobar arteries → arcuate arteries → interlobular arteries
- Afferent arteriole → glomerulus → efferent arteriole (arterial blood)
- Peritubular capillaries and vasa recta
- Capillaries drain into interlobular vein → arcuate vein → interlobar vein → renal vein
Nephron and Tubules
- Diagram of nephron with labels for proximal tubule, juxtaglomerular apparatus, efferent arteriole, afferent arteriole, artery, vein, peritubular capillaries, loop of Henle, distal tubule, collecting duct, renal corpuscle (glomerulus, Bowman's capsule), cortex, and medulla.
Renal Circulation (additional points)
- It is a portal circulation (2 sets of capillaries).
- Glomerulus specialized for filtration.
- Reabsorption occurs in peritubular capillaries
Renal Blood Flow
- 20-25% of cardiac output
- 1140 ml/min
- 90% supplies the cortex
Renal Fraction
- 21% proportion of cardiac output (COP) that goes to the kidney
Renal Plasma Flow
- 625 ml/min (55% of renal blood flow; RBF)
- Calculated by para-aminohippuric (PAH) acid clearance
Plasma Clearance
- Volume of plasma cleared of a substance by the kidney per minute
- Formula: Cx = (Ux × V)/ Px
- Ux = Urine concentration of substance x
- V = Rate of urine flow
- Px = Plasma concentration of substance x
PAH Acid Clearance
- Para-aminohippuric acid (PAHA) clearance: used to measure renal plasma flow, reflecting renal function.
- PAHA is completely removed from blood passing through kidneys (via glomerular filtration and tubular secretion)
- Rate of PAHA clearance from blood reflects total renal plasma flow
Renal Plasma Flow Calculation (ERPF)
- ERPF (effective renal plasma flow) = (U × V) / P
Urine Formation
-
3 basic processes:
- Glomerular filtration (GF)
- Tubular reabsorption (TR)
- Tubular secretion (TS)
-
20% of plasma entering glomerulus is filtered (glomerular filtrate = 125 ml/min)
-
80% of plasma entering glomerulus is not filtered and leaves via efferent arteriole
Regulation of Renal Blood Flow (RBF)
- Autoregulation: aims to maintain constant RBF & GFR despite changes in mean arterial blood pressure (75–160 mmHg). Mechanisms include myogenic and tubuloglomerular feedback.
- Extrinsic control (sympathetic): Intentionally adjusts GFR to regulate arterial blood pressure (ABP).
Autoregulation Mechanisms
- Myogenic: a direct response to stretch induced by changes in blood pressure
- Tubular glomerular feedback: The macula densa cells in the distal tubule sense changes in NaCl concentration. This triggers feedback mechanisms (vasoconstriction/vasodilation of afferent arterioles) to maintain constant GFR.
Autoregulation within ABP Ranges (75-160 mmHg)
- GFR and RBF remain relatively constant despite fluctuations in ABP within this range.
Extrinsic control
- Adjusts GFR as needed to control Blood pressure by targeting afferent arteriole to either constrict or dilate.
- Overrides autoregulation within the normal BP range.
- Mediated by the sympathetic nervous system
Additional Points to Remember
- Renal blood flow (RBF) is approximately 1/4 of cardiac output.
- RBF is regulated by extrinsic and intrinsic factors, including autoregulation.
- Clearance of a substance represents the volume of plasma cleared from that substance per minute.
- Renal plasma flow is measured using para-aminohippuric acid (PAH) clearance.
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