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ESA3 - Urinary System > Renal Blood Flow and GFR > Flashcards

Renal Blood Flow and GFR Flashcards

1
Q

Through which vessels does blood need to travel to get to the glomerulus from the aorta?

A 
Abdominal aorta
Renal artery
Segmental artery
Lobular artery
Arcuate artery
Interlobular artery
Afferent arteriole
Glomerulus
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2
Q

After blood leaves the glomerulus, what vessels does it have to pass through to get into the inferior vena cava?

A 
Glomerulus
Efferent arteriole
Peritubular capillaries/vasa recta
Interlobular vein
Arcuate vein
Lobular vein
Segmental vein
Renal vein
IVC
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3
Q

What are the two types of nephron?

A

Cortical and juxtamedullary

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4
Q

Describe the differences in the loop of henle between the cortical and juxtamedullary nephrons

A

Cortical: Short loop of henle, only just penetrates medulla

Juxtamedullary: Long loop of henle, penetrates deep into the medulla

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5
Q

Describe the differences in the capillaries between the cortical and juxtamedullary nephrons

A

Cortical: efferent arterioles go on to form peritubular capillaries

Juxtamedullary: efferent arterioles go on to form vasa recta

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6
Q

What is the difference in location between cortical and juxtamedullary nephrons?

A

Cortical: outer part of cortex
Juxtamedullary: inner part of cortex, next to medulla

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7
Q

What is the difference in diameter of AA/diameter of EE between cortical and juxtamedullary nephrons?

A

Cortical: AA>EA
Juxtamedullary: AA=EA

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8
Q

Which is the most common type of nephron?

A

Cortical

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9
Q

How much of the blood from the renal artery is filtered at any one time?

A

20%

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10
Q

What is the renal corpuscle?

A

The glomerulus and bowman’s capsule

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11
Q

What is the function of the renal corpuscle?

A

To produce ultra filtrate of plasma

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12
Q

What epithelia does the partietal layer of bowman’s capsule consist of?

A

Simple squamous

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13
Q

What are podocytes?

A

Podocytes are cells in the Bowman’s capsule in the kidneys that wrap around capillaries of the glomerulus

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14
Q

What is the filtration barrier produced by?

A

Fenestrated capillary endothelium and visceral layer of bowman’s capsule

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15
Q

How many layers make up the filtration barrier?

A

3

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16
Q

What are the layers of the filtration barrier?

A

1) Capillary endothelium - permeable to water, salts, glucose - filtrate moves between cells
2) Basement membrane - acellular - permeable to small proteins
3) Podocyte layer - pseudopodia interdigitate forms filtrations slits - provide a defined gap

17
Q

What are the layers of the bowman’s capsule?

A

1) Parietal layer (simple squamous epithelia)
2) Bowman’s space - between parietal and visceral layers where filtrate enters after passing through the filtration slits
3) Visceral layer - made up of podocytes
4) Filtration barrier

18
Q

Why is the basement membrane of the filtration barrier impermeable to most proteins?

A

It’s made up of glycoproteins which are negatively charge so these repel protein movement

19
Q

What effective molecular radius does a substance need to be under to get through the filtration barrier?

A

Radius less than 1.48nm will pass through

20
Q

What is the effect of charge on the passage of substances through the filtration barrier?

A

Positively charged - better clearance (even a substance thats a bit bigger will clear better than a smaller substance that is less positive)

Negatively charged - does not pass through as well (due to glycoproteins in the basement membrane)

21
Q

How can a nephrotoxic substance lead to proteinuria?

A

It can strip the negative charge from the basement membrane layer and allow the passage of negatively charged proteins which end up in the urine

22
Q

What are the 3 forces involved in plasma filtration?

A

1) Hydrostatic pressure in the capillary - regulated (Pgc)
2) Hydrostatic pressure in bowman’s capsule (Pbc)
3) Oncotic pressure difference between capillary and tubular lumen (πgc)

23
Q

Which ways are the forces moving in plasma filtration? Thus, what is the net filtration direction?

A

1) Hydrostatic pressure in capillary - moves plasma into bowman’s capsule
2) Hydrostatic pressure in bowman’s capsule - moves plasma into capillary
3) Oncotic pressure difference - moves plasma into capillary

Net movement = capillary into bowmans because the hydrostatic pressure in the capillary is greater than the other forces

24
Q

In what ways is renal autoregulation achieved?

A

Myogenic mechanisms and tubuloglomerular feedback

25
Q

What is the myogenic mechanism?

A

The myogenic mechanism is how arteries and arterioles react to an increase or decrease of blood pressure to keep the blood flow within the blood vessel constant.

26
Q

If someone has a decreased GFR, how does the kidney respond?

A

Attempts to increase GFR

Dilate AA, Constrict EA

27
Q

If someone has an increased GFR, how does the kidney respond?

A

Attempts to decrease GFR

Constrict AA, Dilate EA

28
Q

How does the dilation of afferent arterioles/constriction of efferent arterioles help to increase GFR?

A

Dilation of AA - allows more blood to come in
Constriction of EA - keeps blood there for longer

This all increases hydrostatic pressure in the capillary

29
Q

How do auto-regulatory mechanisms keep GFR within normal limits?

A

Increase in blood pressure leads to afferent arteriole constriction, so GFR remains unchanged

(would go up otherwise)

Decrease in blood pressure leads to afferent arterioles dilation, so GFR remains unchanged

(would go down otherwise)

30
Q

What does the mechanism of TG feedback link?

A

Sodium and chloride concentration at the macula densa with control of renal arteriolar resistance

31
Q

What does TG feedback act in response to

A

Acute perturbations in the delivery of fluid and solutes to the JGA

32
Q

What cells sense the tubular flow rate as a result of changes in GFR?

A

Macula densa cells

33
Q

How do the macula densa cells sense changes in GFR?

A

Eg increased GFR leads to an increase in [Na+] and [Cl-] in the DCT

Senses changes of NaCl in DCT via a concentration-dependent salt uptake via NaKCC co-transporter in the apical membrane of MD cells (detects increased Cl-)

34
Q

What happens when the macula densa cells detect too little flow through the nephron?

A

Assumes a decrease in GFR, responds to attempt to increase GFR

Stimulates JGA to release chemicals
Prostaglandins vasodilate afferent arterioles

Increased glomerular capillary hydrostatic pressure

GFR goes up

35
Q

What happens when the macula densa cells detect an increase in NaCl in the DCT?

A

Respond by trying to decrease GFR

Stimulates JGA to release chemicals

Adenosine works on A1 receptors to constrict afferent arterioles and works on A2 receptors to vasodilate efferent arterioles

Decreased glomerular capillary hydrostatic pressure

GFR goes down

36
Q

Which transporter detects the increase in Cl-?

A

NaKCC in apical membrane of MD cells

37
Q

Aside from the myogenic response and TG feedback, what is the third autoregulatory mechanism?

A

Glomerulotubular balance - blunts sodium excretion by always reabsorbing 67% of the filtered load

38
Q

How do you calculate filtered load?

A

Filtered load = GFR x concentration

ESA3 - Urinary System (16 decks)

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