45 Questions
What is the role of the juxtaglomerular apparatus in renal homeostasis?
Regulating blood and urine volume
What is the function of the renal arteries in the kidney?
Supplying blood to the kidney
Which structure surrounds the outside of the kidney?
Capsule
Where do the renal arteries pass into after entering the kidney?
Interlobular vessels
What is the 'gold standard' for measuring GFR?
Inulin clearance
Which substance is completely filtered from the plasma and not reabsorbed?
Inulin
What substance overestimates GFR by 10-20% due to active secretion?
Creatinine
What is used to measure renal plasma flow?
Para-amino-hippuric acid
'Clearance' of a substance Cs is given by which formula?
$Cs = \rac{[Us]V},{[Ps]}$
'Normal GFR (both kidneys) is approximately how many mL/min?'
$120-125$ mL/min
How is GFR autoregulated?
By the balance of constriction in the smooth muscle of afferent and efferent arterioles.
Which cells release local chemicals to modulate the contraction of the smooth muscle around the afferent arteriole?
Macula densa cells
What do cells in the macula densa detect to regulate GFR?
Concentration of sodium in the distal tubular fluid.
Which structure controls autoregulation of GFR?
Juxtaglomerular apparatus (JGA)
'Clearance' to measure renal plasma flow equals what product?
[PAH] urine x urine flow = RPF (mL/min)
'Normal creatinine clearance for women falls within which range?'
$88-128$ mL/min
What is the function of the glomerulus in the kidney?
Filtration of blood continuously
Which structure forms a bag enclosing the glomerulus in the kidney?
Bowman's capsule
What is the driving force for plasma filtration into the capsular space in the kidney?
Filtration pressure in the glomerulus
What is the filtration fraction, on average, in Bowman's capsule?
Around 20%
What are podocytes responsible for in the kidney's filtration mechanism?
Allowing filtration of smaller molecules while preventing larger ones from passing through
What is the functional unit of the kidney responsible for urine formation?
Nephron
What is involved in the filtration process in the nephron?
Excretion of materials from blood into urine, balanced by filtration, secretion, and reabsorption
What regulates the filtration and excretion mechanisms in the kidney?
Balance between pressure in afferent and efferent arterioles
Approximately how much fluid is filtered through the kidneys per minute?
125 mL/min
What is the formula to estimate creatinine clearance?
$eC_{Cr} = 140 - Age \times Weight_{kg} \times Constant = Serum Creatinine (\mu mol/L)$
What substance is used to measure renal plasma flow?
Para-amino-hippuric acid (PAH)
What substance overestimates GFR by 10-20% due to active secretion?
Creatinine
'Normal creatinine clearance for women falls within which range?'
$88-128 mL/min$
'Normal GFR (both kidneys) is approximately how many mL/min?'
$120-125$
'Clearance' to measure renal plasma flow equals what product?
$[Us]V/[Ps]$
What regulates the filtration and excretion mechanisms in the kidney?
Juxtaglomerular apparatus (JGA)
What substance forms the 'gold standard' for measuring GFR?
Inulin
What cells release local chemicals to modulate the contraction of the smooth muscle around the afferent arteriole?
Macula densa cells
What structure controls autoregulation of GFR?
Afferent arteriole
What is the driving force for plasma filtration into the capsular space in the kidney?
Hydrostatic pressure
Which structure forms a bag enclosing the glomerulus in the kidney?
Bowman's capsule
What regulates the filtration and excretion mechanisms in the kidney?
Juxtaglomerular apparatus
'Clearance' to measure renal plasma flow equals what product?
$C_{inulin} \ imes V$
'Normal creatinine clearance for women falls within which range?'
$90-120$ mL/min
'Clearance' of a substance Cs is given by which formula?
$\rac{Urine_{Cs} \ imes V},{Plasma_{Cs}}$
'Clearance' concept is used to measure GFR. What are the properties of suitable marker substances for this purpose?
'Completely filtered from the plasma and not reabsorbed or secreted.'
'Normal GFR (both kidneys) is approximately how many mL/min?'
$125$-$135$ mL/min
'Clearance' concept is used to measure GFR. What substance overestimates GFR by 10-20% due to active secretion?
$Creatinine$
'Clearance' concept uses marker substances to measure GFR. Which substance is completely filtered from the plasma and not reabsorbed?
$Creatinine$
Study Notes
- Each kidney contains approximately 1 million glomeruli, which are responsible for filtering blood continuously.
- The filtration process takes place in the renal corpuscle, which consists of the glomerulus and Bowman's capsule.
- Bowman's capsule forms a bag enclosing the glomerulus, and blood enters the capillaries of the glomerulus via the afferent arteriole and leaves via the efferent arteriole.
- The filtration pressure in the glomerulus is the driving force for plasma filtration into the capsular space.
- The filtration fraction is the proportion of plasma that is filtered into Bowman's capsule, which is normally around 20%.
- The filtration mechanism is carried out by podocytes, cells covering the outer surface of the capillaries, which have slits that allow the filtration of smaller molecules while preventing larger ones from passing through.
- The nephron is the functional unit of the kidney, which is responsible for urine formation. It consists of the glomerulus, proximal and distal tubules, and the loop of Henle.
- The filtration process in the nephron involves the excretion of materials from the blood into the urine, which is a balance between filtration, secretion, and reabsorption.
- The filtration and excretion mechanisms are regulated by the balance between the pressure in the afferent and efferent arterioles, which is adjusted to maintain a physical pressure of 55 mmHg in the capillaries.
- The amount of fluid filtered through the kidneys is around 125 mL/min, and approximately 2/3 of this water is reabsorbed into the blood in the proximal tubule.
- Clearance is a measure of kidney function, which is determined by the rate of elimination of a substance from the blood. It is measured by the product of the urine concentration and urine flow rate, divided by the plasma concentration.
Test your knowledge of the general organization of the kidney, ureter, bladder & urethra, the parts of the nephron and their roles in urine production, the vasculature of the kidney, the components of juxtaglomerular apparatus and their roles in blood & urine volume regulation, and renal homeostasis.
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