Physiology 3 - Glomerular Filtration Flashcards
What are the three filtration barriers which make up the glomerular membrane?
Glomerular capillary endothelial cells, basement membrane, podocytes
The glomerular capillary endothelial cells act as a barrier to filtration of what?
Red blood cells
The basement membrane and podocytes act as barriers to filtration of what?
Large plasma proteins
Is the basement membrane of the glomerulus positively or negatively charged?
Negative
What is the major determinant of GFR?
Glomerular capillary blood pressure
Does filtration across the glomerular membrane require energy?
No
Does the glomerular capillary blood pressure favour or oppose filtration?
Favour
Does the capillary oncotic pressure favour or oppose filtration?
Oppose
Does the Bowman’s capsule hydrostatic pressure favour or oppose filtration?
Oppose
Does the Bowman’s capsule oncotic pressure favour or oppose filtration?
Favour
What is the net filtration pressure of the glomerulus under normal circumstances?
10mmHg
How can the GFR be regulated extrinsically?
Sympathetic control
If the afferent arteriole constricts, what effect does this have on GFR?
Decreased
If the afferent arteriole dilates, what effect does this have on GFR?
Increased
Why do changes in systemic arterial blood pressure not necessarily result in changes in GFR?
Autoregulation
If the GFR is too high, what effect does tubuloglomerular feedback have to correct this?
Constriction of the afferent arteriole
If the GFR is too low, what effect does tubuloglomerular feedback have to correct this?
Relaxation of the afferent arteriole
The presence of kidney stones causes an increased Bowman’s capsule hydrostatic pressure due to a build-up of fluid in the system. What effect does this have on GFR?
Decreased
The presence of diarrhoea causes dehydration which leads to an increased glomerular capillary oncotic pressure. What effect does this have on GFR?
Decreased
In a patient with severe burns, there will be a decreased glomerular capillary oncotic pressure due to the loss of plasma proteins. What effect does this have on GFR?
Increased
The filtration fraction is defined as the fraction of plasma flowing through the glomeruli that is filtered into the tubules. Under normal circumstances, expressed as a percentage, what would the filtration fraction be?
20%
What substance is ideal for measuring GFR as it is neither absorbed nor secreted in the renal tubules; however, it is not used clinically since it is an exogenous substance?
Inulin
What endogenous substance is best for measuring GFR since only a very small amount of it is secreted?
Creatinine
For substances which are filtered, completely reabsorbed and not secreted, what is the clearance?
0
For substances which are filtered, partly reabsorbed and not secreted, is the clearance more or less than the GFR?
Less
For substances which are filtered, secreted but not reabsorbed, is the clearance more or less than the GFR?
More
