GFR

Question 1

What are the three layers of the glomerular capillary filtration barrier?

Answer 1

capillary endothelium, glomerular basement membrane, podocyte epithelium

Question 2

what is the purpose of the glycocalyx to the barrier function of the endothelial surface layer?

Answer 2

governs transcapillary fluid exchange and acts as a biomechanical sensor; prevents albumin from passing through

Question 3

What cannot pass the filtration barrier? What can?

Answer 3

large molecules (proteins), cells cannot

water, small solutes (glucose, amino acids, electrolytes)

Question 4

What is the tamm-horsfall protein?

Answer 4

most abundant protein excreted in urine; secreted in the loop of henle

Question 5

Damage in which parts of the filtration barrier can result in hematuria and proteinuria?

Answer 5

The basement membrane and glycocalyx

Question 6

What causes proteinuria?

Answer 6

damage to the glomerular basement membrane, which causes the loss of negative charge, which then permits the passage of albumin into the filtrate

Question 7

How does proteinuria influence fluid oncotic and hydrostatic pressure?

Answer 7

capillary oncotic pressure would decrease due to the less protein in the blood

Question 8

How does the anatomical arrangement of the kidney influence nephron function?

Answer 8

the cortex has tubules and vessels that are intertwined whereas the medulla has vessels organized in parallel arrays; blood flow is greater in the cortex than in the medulla; filtration might occur more in the cortex?

Question 9

What is the equation for filtered load?

Answer 9

filtered load of X = plasma concentration of X*GFR

Question 10

what is the equation for urinary excretion?

Answer 10

amount filtered - amount reabsorbed + amount secreted = amount excreted in the urine

Question 11

what is the equation for tubular reabsorption?

Answer 11

glomerular filtration - urinary excretion + amount secreted

Question 12

What is the urinary concentration of x? (Ux)

Answer 12

the concentration of that substance x in the urine in a given volume

Question 13

What is urine flow rate? (V)

Answer 13

the rate at which urine is produced (urine volume/time)

Question 14

what is the urine excretion rate?

Answer 14

the urinary concentration of x (Ux)* the urine flow rate (V)

Question 15

What is renal clearance (C)? What is the equation?

Answer 15

the volume of plasma completely cleared of a substance by the kidneys per unit time; C=(Ux*V)/Px

Question 16

What is the glomerular filtrate?

Answer 16

the volume of plasma filtered into the combined nephrons of both kidneys per unit of time

Question 17

what is the capillary filtration coefficient?

Answer 17

permeability * surface area

Question 18

What is the filtration fraction (FF)?

Answer 18

GFR/RPF; it is the fraction of RBF that is filtered across the glomerulus

Question 19

How does the RBF and GFR change during severe hemorrhage or renal artery stenosis?

Answer 19

RBF decreases so GFR increases to maintain homeostasis

Question 20

How can you use renal clearance to estimate GFR?

Answer 20

GFR is directly proportional if:

1. the substance is freely filterable
2. neither reabsorbed nor secreted
3. not synthesized broken down or accumulated by the kidney
4. physiologically inert

Question 21

compare and contract the use of inulin and creatinine clearances as a measure of GFR

Answer 21

You can use inulin to estimate GFR because its renal clearance is directly proportional; creatinine is also freely filtered but 10% of it is secreted, so its not an ideal marker

Question 22

how does sympathetic stimulation increase blood pressure through: 1. arterial resistance vessels, 2. juxtraglomerular granular cells 3. tubular epithelial cells

Answer 22

1. SNS targets alpha1 receptors on vessels vessels and causes vasoconstriction (afferent>efferent)
2. SNS targets beta1 receptors on juxtaglomerular cells and causes renin release and RAAS
3. SNS targets tubular epithelial cells to increase sodium resorption through the sodium/potassium pump

Question 23

What are the acute effects of SNS on

1. RBF
2. GFR
3. renin secretion
4. sodium resorption?

Answer 23

1. decreased RBF
2. GFR is stabilized
3. renin secretion increases
4. stimulates sodium resorption in PCT and DCT

Question 24

What are the chronic effects of SNS on

1. urinary output
2. sodium excretion
3. water intake?

Answer 24

1. decreased urinary output
2. decreased sodium excretion
3. increased water intake

Question 25

What is the relationship between GFR and the plasma concentration of creatinine?

Answer 25

they are inversely related; as GFR decreases, serum creatinine concentration increases

Question 26

How can you use the BUN/creatinine ratio to know if a pathology is pre, intra or post renal?

Answer 26

if BUN reabsorption is increased, it’s pre-renal, of BUN resorption is decreased, its intra-renal. if BUN is normal, its normal or post renal.

Question 27

How can PAH be used to estimate renal plasma flow?

Answer 27

PAH is freely filtered by the glomerular capillaries and also secreted from the peritubular capillary blood into the tubular lumen, so renal blood flow can be calculated from the clearance of PAH.