Functional perfusion of the kidney

Question 1

Which organ has the highest blood flow per unit mass?

Answer 1

The kidneys

Question 2

What is the average blood flow to the kidney?

Answer 2

1200 mL/min

Question 3

What is the average plasma flow to the kidney?

Answer 3

650 mL/min

Question 4

What percentage of the cardiac output goes to the kidney?

Answer 4

25% of the cardiac output

Question 5

What percentage of body weight do the kidneys make up?

Answer 5

Less than 0.5% of the body weight

Question 6

How does the renal circulation divide in the kidneys?

Answer 6

Renal artery -> interlobar arteries -> arcuate arteries -> interlobular arteries -> afferent arterioles that perfuse the glomerulus

Question 7

How many interlobar arteries form from the division of the renal artery?

Answer 7

5 per kidney

Question 8

Along where do the interlobar arteries run on the structure of the kidney?

Answer 8

Up the side of the renal pyramids

Question 9

Where on the renal structure do the interlobar arteries divide into the arcuate arteries?

Answer 9

In the border of the medulla and cortex

Question 10

Why do the kidneys have such high blood flow?

Answer 10

Kidneys need to filter 180 litres a day to maintain homeostasis

Question 11

The kidney is the organ with the highest oxygen uptake

TRUE or FALSE

Answer 11

FALSE

The kidney has the second highest oxygen uptake - after the heart

Question 12

Kidneys have the lowest atriovenous oxygen difference in any organ due to its high blood flow

TRUE or FALSE

Answer 12

TRUE

Question 13

What is the Glomerular Filtration Rate?

Answer 13

Filtration of the renal plasma from the glomerula capillaries into the Bowman’s capsule

Question 14

What is the typical value for GFR?

Answer 14

120 mL/min

Question 15

What is GFR used for?

Answer 15

Best single means of assessing kidney function

Question 16

What is autoregulation?

Answer 16

Method by which the kidney’s GFR and renal blood flow remains constant despite an increase in systemic pressure

Question 17

Why is autoregulation necessary?

Answer 17

Prevents changes in systemic pressure from affecting renal function

Increase in systemic pressure results in no increase in GFR or renal blood flow

Question 18

What is the correlation between renal blood flow and GFR?

Answer 18

Direct correlation

Question 19

Within what range of systemic BP will autoregulation work?

Answer 19

90 - 180 mmHg

Question 20

What are the two mechanisms of autoregulation?

Answer 20

Myogenic mechanism

Tubuloglomerular feedback

Question 21

Which mechanism of autoregulation acts faster?

Answer 21

Myogenic mechanism

Question 22

What is the myogenic mechanism?

Answer 22

Intrinsic capacity of the smooth muscle cells in the afferent arterioles to constrict when distended

Question 23

Describe the steps of the myogenic mechanism

Answer 23

Blood pressure increases

Afferent arterioles stretch

Non-specific cation channels open

Depolarization

Calcium channels open

Afferent arteriole contracts

Question 24

What is the stimulus of the tubuloglomerular feedback?

Answer 24

Concentration of sodium in the DCT

Question 25

What is the stimulus of the myogenic mechanism?

Answer 25

Blood pressure of the afferent arteriole

Question 26

What apparatus regulates the tubuloglomerular feedback?

Answer 26

The juxtaglomerular apparatus

Question 27

Describe the steps of the tubuloglomerular feedback

Answer 27

Blood pressure increases Afferent arteriole pressure increases GFR increases Increased sodium delivery to the DCT Macula densa cells detect an increase in sodium concentration and release adenosine Afferent arterioles contract

Question 28

What is adenosine?

Answer 28

A purine that acts on purinergic receptors on arterioles

Question 29

Which mechanisms can override autoregulation?

Answer 29

Nerves Hormones

Question 30

Within which range does autoregulation function?

Answer 30

90 - 180 mmHg

Question 31

In which situations do nerves override autoregulation?

Answer 31

In situations of stress or limit of water loss from body Reduction of blood flow to the kidneys

Question 32

How do nerve override autoregulation?

Answer 32

Causes afferent and to some degree efferent arteriolar constriction Reduces renal blood flow and GFR

Question 33

Hormones override autoregulation in response to which situations?

Answer 33

Reduced pressure in the afferent arteriole Increased sympathetic nerve stimulation Decreased sodim in the distal tubule sensed by Macula densa cells

Question 34

Example of hormones that override autoregulation

Answer 34

Renin-angiotensin system

Question 35

Which cells produce renin?

Answer 35

Renin is produced by granular cells located along afferent arterioles in kidneys

Question 36

What are the steps of the renin-angiotensin system?

Answer 36

1. Renin is released from macula densa cells in the afferent arteriole 2. Angiotensinogen is released from the liver 3. Renin acts on Angiotensinogen - converts it to angiotensin I 4. Capillary endothelial in lungs release ACE 5. ACE converts Ang I - Ang II 6. Ang II has various effects

Question 37

What are the effects of Angiotensin II on the pituitary gland?

Answer 37

Causes release of ADH from the pituitary gland

Question 38

What are the effects of Angiotensin II on the adrenal gland?

Answer 38

Releases aldosterone which affects sodium and water reabsorption

Question 39

What are the effects of Angiotensin II on autoregulation?

Answer 39

Overrides autoregulation Can affect both the afferent and efferent arterioles - most receptors are found on the efferent Causes vasoconstriction

Question 40

What are the consequences of vasoconstriction of the renal arterioles?

Answer 40

Reduce renal blood flow through the capillaries Increases pressure in the capillaries Increases GFR

Question 41

What is the consequences of high Ang II concentration?

Answer 41

Vasoconstriction of both afferent and efferent arterioles

Question 42

When is Ang II released in high concentration?

Answer 42

After a haemorrhage Makes blood flow away from the kidney and to other important organs Reduces GFR and renal blood flow

Question 43

What are the consequences of renal blood flow and GFR following low conc of Ang II vs high conc of Ang II release?

Answer 43

Low concentration - efferent vasoconstriction. GFR increases whilst blood flow decreases High concentration - afferent and efferent vasoconstriction. GFR and blood flow decrease