Vanders Renal Ch2 Flashcards
What is renal blood flow (RBF)?
1 L/min, representing 20% of resting cardiac output
RBF is significant given that the kidneys constitute less than 1% of body mass.
What is the normal glomerular filtration rate (GFR)?
Approximately 125 mL/min
GFR is a key indicator of kidney function.
What formula relates flow, pressure, and resistance in any vascular bed?
Q = ΔP / R
Q is blood flow, ΔP is the pressure difference, and R is resistance.
What are the successive vessels blood flows through after leaving the renal artery?
Arcuate arteries, interlobular arteries, afferent arterioles, glomeruli
These vessels are crucial for delivering blood to the kidney’s filtration units.
What are the relative resistances of afferent and efferent arterioles?
About equal under most circumstances
Both types of arterioles account for most of the total renal vascular resistance.
How do changes in afferent and efferent arteriolar resistances affect renal blood flow?
They can be additive or offsetting depending on the direction of change
Changes in resistance can significantly impact renal blood flow.
What are the three layers of the glomerular filtration barrier?
Endothelial cells, capillary basement membrane, podocytes
Each layer has unique structures that contribute to filtration.
Define podocyte.
Epithelial cells that surround glomerular capillaries
Podocytes have foot processes that create filtration slits.
What determines the filterability of plasma solutes?
Molecular size and electrical charge
The structure of the filtration barrier restricts certain solutes based on these factors.
What is the filtration fraction?
The fraction of renal plasma flow that is filtered into the Bowman’s capsule
It is a measure of kidney function efficiency.
Why is the net filtration pressure in glomerular capillaries positive?
High hydrostatic pressure in glomerular capillaries
This pressure drives fluid out of the capillaries into the Bowman’s capsule.
What is autoregulation of renal blood flow?
The ability of the kidneys to maintain a constant blood flow despite changes in arterial pressure
This mechanism ensures stable kidney function.
What is the significance of the high blood flow through the peritubular network in the cortex?
Maintains interstitial environment close to blood plasma composition
This is crucial for the function of renal tubules.
What is the typical blood flow through the vasa recta into the medulla?
Approximately 0.1 L/min
Although low compared to cortical blood flow, it is sufficient for medullary function.
What is the role of hydrostatic pressures in the glomerular and peritubular capillaries?
High in glomerular capillaries for filtration, low in peritubular capillaries for reabsorption
This difference is essential for kidney function.
How does molecular size affect filterability?
Molecules < 7000 Daltons are freely filtered; larger molecules are restricted
Plasma albumin is largely excluded due to its size.
Fill in the blank: The primary function of the glomerular filtration barrier is to restrict the passage of _______.
plasma proteins
This selectivity is crucial for maintaining protein levels in the blood.
True or False: The glomerular filtrate contains significant amounts of albumin.
False
Albumin is largely restricted from passing through the filtration barrier.
What happens to filterability as molecular weight increases?
Filterability declines as molecular weight increases, especially above 70,000 Da.
Which type of macromolecules are filtered to a lesser extent?
Negatively charged macromolecules are filtered to a lesser extent than neutral molecules.
What is the role of electrical charge in the filtration process?
Electrical charge enhances filtration restriction; negatively charged molecules are repelled, while positively charged molecules are filtered more easily.
What is the significance of the filtration coefficient (Kf)?
Kf denotes the product of hydraulic permeability and surface area of the glomerular capillaries.
What are the Starling forces involved in glomerular filtration?
Starling forces are the algebraic sum of hydrostatic and oncotic pressures across the capillary wall.
What is the average net filtration pressure in glomeruli?
The average net filtration pressure is about 16 mm Hg.
How does an increase in afferent arteriolar resistance affect glomerular pressure?
It decreases glomerular pressure.
Fill in the blank: The filtration fraction is the ratio of _______.
GFR/RPF
What happens to GFR during exercise?
GFR decreases considerably during exercise.
True or False: Hydrostatic pressure in Bowman’s capsule usually has a significant impact on GFR.
False.
What is the effect of increased arterial oncotic pressure on GFR?
Increased arterial oncotic pressure tends to reduce GFR.
What is filtered load?
The amount of substance filtered per unit time, calculated as GFR multiplied by plasma concentration.
What physiological mechanisms are collectively called autoregulation?
Mechanisms that minimize changes in GFR and RBF despite fluctuations in renal artery pressure.
How does renal artery pressure affect glomerular pressure?
Changes in renal artery pressure cause changes in glomerular pressure in the same direction.
What happens to GFR if renal artery pressure remains constant?
GFR is maintained nearly constant despite fluctuations in arterial pressure.
What is the impact of low renal blood flow (RBF) on glomerular oncotic pressure?
Low RBF leads to a steeper increase in glomerular oncotic pressure, lowering average net filtration pressure and GFR.
What is the typical percentage of plasma filtered by the kidneys?
About 20% of the plasma entering the kidney is filtered.
What happens to net filtration pressure as water is filtered out of the glomerular capillaries?
Net filtration pressure decreases due to increased oncotic pressure as proteins are left behind.
What regulates blood flow in the kidneys relative to their mass?
Functional reasons rather than metabolic demand.
What determines glomerular capillary pressure?
The relative resistances of afferent and efferent arterioles.
What is the structure through which glomerular filtration proceeds?
A three-layered barrier that restricts filtration of large macromolecules.
What type of charge on the filtration barrier restricts negatively charged solutes?
Negative surface charge.
What determines the glomerular filtration rate (GFR)?
Permeability of the filtration barrier and net filtration pressure (NFP).
What primarily affects net filtration pressure (NFP)?
Hydrostatic and oncotic pressures in the glomerular capillaries.
What allows for independent control of glomerular filtration rate and renal blood flow?
Control of the resistances of the afferent and efferent arterioles.
True or False: Autoregulation prevents large changes in GFR with changes in arterial pressure.
True.
Blood enters the renal medulla immediately after passing through which vessels?
Arcuate arteries.
Which cell type is the main determinant of the filterability of plasma solutes?
Podocyte.
Which one of the following is NOT subject to physiological control on a moment-to-moment basis?
Selectivity of the filtration barrier.
A substance is freely filtered and has a certain concentration in peripheral plasma. You would expect the substance to have virtually the same concentration in _______.
the glomerular filtrate.
In the face of a 20% decrease in arterial pressure, GFR decreases by only 2%. What could account for this finding?
Efferent arteriolar resistance increases.
The hydrostatic pressure within the glomerular capillaries is _______.
much higher than in most peripheral capillaries.
