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PHS3300 Renal Pathophysiology Exam Study Guide
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PHS3300 Renal Pathophysiology ExamStudy Guide
renal blood flow: how much blood does the kidney receive per minute?
what is this in comparison with the cardiac output? - Answer both kidneys receive 1200
ml or 1.2 L per minute.
25% of CO - 10% of blood travels to medulla (collecting duct, reabsorption, secretion,
excretion), where 90% of blood travels to the cortex (glomerulus --> filtration unit)
How much blood that enters the kidney is absorbed back into the body/ how much ends
up excreted in urine? - Answer 99% (180L filtred/24 hours) absorbed.
1% (1-1.8 L of urine) excreted
describe the structure of a kidney including how many glomeruli are present, the inner
section of the kidney, the outer most section of the kidney, and the arterioles that blood
travels through to get into a glomerulus + the ones it uses to get out - Answer 1 millions
glomeruli in each kidney .medulla is inner most point of kidney. cortex is outer most
part.
Blood comes in through afferent arteriole to glomerulus. It is then filtered through many
capillaires (made of epithelial cells where filtration occurs. Now, blood exits through
efferent arterioles. Urine is eventually produced (this contains no albumin (blood
protein). Should contain no proteins... if we are loosing proteins, we can be at risk of
edema.
what can we use to test kidney function? - Answer calculate the glomerular filtration
rate (GFR)
GFR (glomerular filtration rate)
what is it and what units is it measured in? - Answer Rate at which plasma moves
through glomerular capillaries
ml/min
the volume of fluid filtered from the glomerular capillaries into Bowman's capsule per
unit time. Clinically, GFR is measured to determine renal function.
do males and females have a different GFR? what accounts for the difference?
when do children have adult proportions? - Answer •Females 85-125 ml/min, Males
97-140 ml/min for two kidneys - WHY is there a difference? Males have larger kidneys.
by 2 years of age
,what is the driving force for GFR? - Answer Glomerular capillary hydrostatic pressure
(postive force). Every time our heart beats, it pushes blood through renal arteries and
push blood into afferent arterioles. There is a drop in blood pressure as the diameter of
each vessel gets smaller towards the kidney. .
how would plasma concentration levels of creatine reflect the GFR of a patient suffering
from chronic kidney disease (CKD?) - Answer •If GFR decreases (due to CKD), then
excretion < production for creatinine, so plasma [Cr] increases.
New steady-state is reached where excretion is almost = to production.
Plasma [Cr] is now increased
does plasma levels of creatinine concentration reflect GFR in steady state conditions?
name 5 reasons why creatinine reflects a GFR in steady state conditions. - Answer yes.
•Creatinine is produced by skeletal muscle at a constant rate
•
•Creatinine is excreted mainly by filtration I.e. GFR X plasma [Cr]
•
•Renal excretion = Muscle production
•
•Therefore, Plasma [Cr] is constant under normal circumstances
•
•Range of normal plasma [Cr] is 50-110 µmol/L - depends on factors like muscle mass.
Johnny is suffering from type 2 diabetes, in which is GFR has been elevated. What do
you expect to occur to his creatinine levels?
How about if Johnny had kidney disease? - Answer they should decrease due to
filtration rate being elevated... more creatinine is being excreted in the urine.
If kidney disease, creatinine concentration goes up since it isn't being excreted.
describe the 4 characteristics of a substance that must apply in order for it to be used to
measure GFR - Answer must be freely filtered
must not be reabsorbed or secreted
must not alter GFR: it can't be a factor that would change GFR - like a hormone for
example.
must not be synthesized or catabolized by the kidney: We don't want it to be made in the
, kidney or broken down in the kidney
substances used to measure GFR:
which substance is referred to as the "gold standard" - Answer inulin. very innert.
However, this is not practical to measure GFR in family clinics.
substances used to measure GFR:
what is the clinical standard substance? how is it done clinically? what is it? excretion
method? what is it produced by? - Answer creatinine!
•provide a blood sample and they measure its levels in blood. This is a normal metabolic
product of muscles. If you have more muscle mass, you have more creatine. Rate at
which it gos through kidneys is constant.
-Creatinine is excreted mainly by filtration
-Creatinine is produced by skeletal muscle at a constant rate from creatine-phosphate
substances used to measure GFR: other than inulin and creatinine, what other
substance did we discuss? - Answer Cystatin C: made by all cells in the body that have
nuclei. Gets spit out into blood
the amount excreted (X), is equal to - Answer amount filtered - amount reabsorbed +
amount secreted
GFR = [Uinulin]V/[Pinulin]. Using the following equation, we can see that the plasma
concentration of inulin times the GFR is equal to what? - Answer the amount that is
excreted (amount in urine) times the volume of urine over that period of time
what is the equation used to calculate GFR?
what does this calculation require clinically? - Answer amount excreted times volume of
urine produced over period/ amount in plasma
for example, for creatinine, the equation would look like this:
GFR= [Cr] urine x urine flow rate
______________________________
[Cr] in plasma
•Requires
-12-24 hr urine collection (timed)
-mid-point blood sample
[Cr] in urine and plasma.
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