Renal Hemodynamics and blood flow- Lee

Question 1

80% of the blood supply in the kidney is located where?

Answer 1

renal cortex

Question 2

Where is the macula densa located?

Answer 2

in the lumen of the nephron in the DCT

Question 3

What are the two substance that are primarily used to measure GFR?

Answer 3

inulin and creatinine

Question 4

What is the largest pressure force in determining GFR?

Answer 4

glomerular capillary hydrostatic pressure

roughly 50 mmHg

Question 5

What are the factors that can affect filtration fraction ?

Answer 5

• decreased renal plasma flow

- decreased GFR

Question 6

Substances that are not filtered through the glomeruli return to the blood through which vessel?

Answer 6

efferent arteriole

Question 7

How does size and charge affect filterability?

Answer 7

Positive charged substances are more readily filtered than negative charged substances.

Small sized particles are more easily filtered than large sized particles.

Question 8

T/F. Even though an individual has a high concentration of glucose all of it will be filtered at the glomeruli.

Answer 8

True

Question 9

What is microalbuminuria and what are causes of it?

Answer 9

urine excretion of albumin >30 but <150 mg per day

• early DM
• HTN
• glomerular hyperfiltration

Question 10

What are the forces that oppose filtrate movement out of the glomeruli capillary?

Answer 10

• glomerular colloid osmotic pressure

- Bowman’s capsule pressure

Question 11

What is hydronephrosis and what causes it?

Answer 11

Hydronephrosis is the swelling of a kidney due to a build-up of urine.

causes: tubular obstruction ???

Question 12

What is Kf? What is significant about its value in the kidney? How can it be reduced?

Answer 12

• it is a filtration coefficient that is important in determining GFR
• it is normally 12.5 ml/min in the kidneys which is 400 times greater than Kf in other tissues
• it can be reduced by chronic HTN, obesity/ DM, glomerulonephritis

Kf = hydraulic conductivity x surface area

Question 13

How can DM decrease GFR?

Answer 13

there will be inflammation within the glomerulus which will decrease the surface area for which substances are filtered thus decreasing GFR

Question 14

Give examples of conditions that can increase Bowman’s capsule hydrostatic pressure.

Answer 14

• tubular obstruction
• kidney stones
• tubular necrosis
• urinary tract obstruction
• prostate hypertrophy/cancer

Question 15

The accumulation of proteins is higher at the end of the capillary than at the beginning. This accounted for by what?

Answer 15

increasing glomerular capillary oncotic pressure

Question 16

________in afferent arteriole resistance and __________in efferent arteriole resistance will cause increase in glomerular capillary hydrostatic pressure. How is renal blood flow affected by constriction in the afferent arteriole vs. the efferent arteriole?

Answer 16

decrease
increase

renal blood flow will decrease in increases in both afferent and efferent arteriolar resistance

Question 17

Why do increases in arterial pressure not substantially change glomerular capillary hydrostatic pressure?

Answer 17

important for maintaining GFR

Question 18

Decreases in glomerular filtration rate will________ in glomerular capillary hydrostatic pressure causing what type of renal disease?

Answer 18

decrease

pre-renal???

Question 19

Overtime as efferent arteriole resistance increase, the GFR begins to go down. Why?

Answer 19

Overtime decreased renal blood flow will lead to lower amounts of blood needed to maintain a normal GFR

Question 20

What are the four Starling forces?

Answer 20

The four Starling forces are:

• hydrostatic pressure in the capillary
• hydrostatic pressure in the interstitium
• oncotic pressure in the capillary
• oncotic pressure in the interstitium

Question 21

How does increase in efferent arteriole (Re) resistance result in increase in GFR although Re causes increase in glomerular capillary oncotic pressure?

Answer 21

glomerular capillary oncotic pressure is significantly less than glomerular capillary hydrostatic pressure

Question 22

A large fraction of renal oxygen consumption is related to what?

Answer 22

renal tubular sodium reabsorption

Question 23

Severe hemorrhage will result in what effects to the GFR?

Answer 23

decrease in GFR

as the afferent and efferent arteriole resistance will increase (afferent significantly higher)

Question 24

Low sodium diet and volume depletion will result in what effects to the GFR?

Answer 24

increase in the efferent arteriole resistance which will maintain the GFR

you do not want an increase in GFR because you want to conserve volume to get pressure back to normal

low sodium diet decreases water reabsorption

Question 25

What is the juxtaglomerular apparatus made up of?

Answer 25

• juxtaglomerular cells (granular cells which are specialized smooth muscle cells)
• extraglomerular mesangial cells
• macula densa

Question 26

What innervates granular cells?

Answer 26

sympathetic nervous system

Question 27

When tubular filtrate is low across the macula densa or there is low sodium what occurs?

Answer 27

vasodilation

Question 28

Why do patients with atherosclerosis have a greater risk for excessive decrease in GFR in response to volume depletion?

Answer 28

patients with atherosclerosis have endothelial damage and thus do not have functioning epithelium to produce NO

endothelial derived nitric oxide protects against excessive vasoconstriction

Question 29

What is the myogenic mechanism for autoregulation of GFR and renal plasma flow?

Answer 29

vascular smooth muscle cells in the afferent arteriole that are responsive to stretch; when stretched there is calcium influx thus causing muscle cells to contract preventing further increases in GFR and RBF

Question 30

T/F. Angiotensin II contributes to GFR but not RBF autoregulation.

Answer 30

TRUE

Question 31

What substances should be normally 100% reabsorbed back into the blood?

Answer 31

• glucose
• amino acids
• lactate

Question 32

If angiotensin II is blocked, what happens to GFR autoregulation?

Answer 32

GFR autoregulation is impaired

Question 33

What are the three stages of pre-renal acute kidney injury?

Answer 33

pre-renal
intra-renal
post-renal

Question 34

How can pre-renal, intrarenal, and post-renal acute kidney injury be caused?

Answer 34

pre-renal: hypoperfusion

intrarenal: nephrosclerosis, damage to the glomerulus

post-renal: obstruction (kidney stones)