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Kidneys and Hormones > Functional perfusion of the kidney > Flashcards

Functional perfusion of the kidney Flashcards

1
Q

Which organ has the highest blood flow per unit mass?

A

The kidneys

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2
Q

What is the average blood flow to the kidney?

A

1200 mL/min

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3
Q

What is the average plasma flow to the kidney?

A

650 mL/min

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4
Q

What percentage of the cardiac output goes to the kidney?

A

25% of the cardiac output

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5
Q

What percentage of body weight do the kidneys make up?

A

Less than 0.5% of the body weight

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6
Q

How does the renal circulation divide in the kidneys?

A

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

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7
Q

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

A

5 per kidney

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8
Q

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

A

Up the side of the renal pyramids

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9
Q

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

A

In the border of the medulla and cortex

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10
Q

Why do the kidneys have such high blood flow?

A

Kidneys need to filter 180 litres a day to maintain homeostasis

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11
Q

The kidney is the organ with the highest oxygen uptake

TRUE or FALSE

A

FALSE

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

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12
Q

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

TRUE or FALSE

A

TRUE

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13
Q

What is the Glomerular Filtration Rate?

A

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

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14
Q

What is the typical value for GFR?

A

120 mL/min

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15
Q

What is GFR used for?

A

Best single means of assessing kidney function

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16
Q

What is autoregulation?

A

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

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17
Q

Why is autoregulation necessary?

A

Prevents changes in systemic pressure from affecting renal function

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

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18
Q

What is the correlation between renal blood flow and GFR?

A

Direct correlation

19
Q

Within what range of systemic BP will autoregulation work?

A

90 - 180 mmHg

20
Q

What are the two mechanisms of autoregulation?

A

Myogenic mechanism

Tubuloglomerular feedback

21
Q

Which mechanism of autoregulation acts faster?

A

Myogenic mechanism

22
Q

What is the myogenic mechanism?

A

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

23
Q

Describe the steps of the myogenic mechanism

A

Blood pressure increases

Afferent arterioles stretch

Non-specific cation channels open

Depolarization

Calcium channels open

Afferent arteriole contracts

24
Q

What is the stimulus of the tubuloglomerular feedback?

A

Concentration of sodium in the DCT

25
Q

What is the stimulus of the myogenic mechanism?

A

Blood pressure of the afferent arteriole

26
Q

What apparatus regulates the tubuloglomerular feedback?

A

The juxtaglomerular apparatus

27
Q

Describe the steps of the tubuloglomerular feedback

A

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

28
Q

What is adenosine?

A

A purine that acts on purinergic receptors on arterioles

29
Q

Which mechanisms can override autoregulation?

A

Nerves

Hormones

30
Q

Within which range does autoregulation function?

A

90 - 180 mmHg

31
Q

In which situations do nerves override autoregulation?

A

In situations of stress or limit of water loss from body

Reduction of blood flow to the kidneys

32
Q

How do nerve override autoregulation?

A

Causes afferent and to some degree efferent arteriolar constriction

Reduces renal blood flow and GFR

33
Q

Hormones override autoregulation in response to which situations?

A

Reduced pressure in the afferent arteriole

Increased sympathetic nerve stimulation

Decreased sodim in the distal tubule sensed by Macula densa cells

34
Q

Example of hormones that override autoregulation

A

Renin-angiotensin system

35
Q

Which cells produce renin?

A

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

36
Q

What are the steps of the renin-angiotensin system?

A
  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
37
Q

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

A

Causes release of ADH from the pituitary gland

38
Q

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

A

Releases aldosterone which affects sodium and water reabsorption

39
Q

What are the effects of Angiotensin II on autoregulation?

A

Overrides autoregulation

Can affect both the afferent and efferent arterioles - most receptors are found on the efferent

Causes vasoconstriction

40
Q

What are the consequences of vasoconstriction of the renal arterioles?

A

Reduce renal blood flow through the capillaries

Increases pressure in the capillaries

Increases GFR

41
Q

What is the consequences of high Ang II concentration?

A

Vasoconstriction of both afferent and efferent arterioles

42
Q

When is Ang II released in high concentration?

A

After a haemorrhage

Makes blood flow away from the kidney and to other important organs

Reduces GFR and renal blood flow

43
Q

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

A

Low concentration - efferent vasoconstriction. GFR increases whilst blood flow decreases

High concentration - afferent and efferent vasoconstriction. GFR and blood flow decrease

Kidneys and Hormones (39 decks)

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