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Cardiovascular, Respiratory and Renal Systems > L24 Renal Perfusion and Glomerular Filtration > Flashcards

L24 Renal Perfusion and Glomerular Filtration Flashcards

1
Q

The blond end of a nephron is called the __?__

A

Bowman’s capsule

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2
Q

The outer __1__ layer of the Bowman’s capsule is continuous with the outer layer of the __2__. It then has a __3__ space (where filtrate collects) and an inner __4__ layer composed of podocytes (which __5__)

A
  1. parietal
  2. Renal tubule
  3. capsular
  4. visceral
  5. envelop glomerular capillaries
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3
Q

What is a pedicel?

A

The distal processes of a podocyte

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4
Q

True or false: The glomerular filter produces an ultrafiltrate of plasma

A

True

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5
Q

The glomerular filter is made of which of the following:

A) Endothelium
B) Basement membrane
C) Podocytes
D) All of the above

A

D) All of the above

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6
Q

The capillaries that pass through the glomerulus are __?__ (50-100x leakier than normal).

A

Fenestrated

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7
Q

True or false: The glomerular filter allows cells and platelets through. These are reabsorbed later.

A

False.

Although fenestrated, cells and platelets cannot escape the capillary endothelium and are retained in the blood vessel

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8
Q

The basement membrane of of the glomerular filter is the main barrier. From where does the basement membrane originate? What is made of?

A

It is secreted by podocytes, made from collagen and glycoproteins

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9
Q

True or false: The basement membrane of the glomerular filter is positively charged to repel cations.

A

False. The basement membrane of the glomerular filter is negatively charged to repel anions.

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10
Q

Why is proteinuria checked in urinalysis?

A

Protein should not cross the glomerular filter. Presence of protein in urine is an indication of renal damage.

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11
Q

Which cell is responsible for maintaining the basement membrane in the glomerular filter?

A

Podocytes

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12
Q

True or false: Podocytes are phagocytic

A

True. Podocytes trap escaping cells and macromolecules via phagocytosis

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13
Q

True or false: Podocytes are coated in a negatively-charged glycocalyx coating

A

True

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14
Q

What feature of the glomerular filter means virtually no proteins can cross into the tubule?

A

Negative charge prevents other negatively charged molecules crossing (I guess many proteins are negatively charged)

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15
Q

Which of the following will be freely filtered in the glomerulus?

A) A positively charged molecule, 6000 daltons
B) A positively charged molecule 500 daltons
C) A negatively charged molecule, 500 daltons
D) A negatively charged molecule, 6000 daltons
E) A and B
F) B and C
G) All of the above

A

E) A and B

Free filtration of molecules below 7000 daltons; virtually no filtration above 70,000.

Negative charges prevent filtration of negatively charged molecules.

Glucose, amino acids, salts and urea are all freely filtered.

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16
Q

Which of the following is NOT freely filtered in the glomerulus?

A) Glucose
B) Amino acids
C) Urea
D) Albumin

A

D) Albumin

Albumin is a protein that is over 68 000 daltons - close to the upper limit for filtration.

It is also negatively charged, therefore is repelled by the negatively charged filter.

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17
Q

Which of the following starling forces is normally (roughly) zero?

A) Bowman’s capsule hydrostatic pressure
B) Capillary hydrostatic pressure
C) Capillary protein oncotic (colloid) pressure
D) Bowman’s capsule protein oncotic (colloid) pressure

A

D) Bowman’s capsule protein oncotic (colloid) pressure

As protein does not get filtered, it can be assumed the colloid pressure in the Bowman’s capsule is zero

18
Q

Hydrostatic pressure and protein oncotic pressure are examples of what forces?

A

Starling forces

19
Q

Why is the hydrostatic pressure higher in the glomerular capillary bed than in a typical capillary?

A

Most capillary beds have an arteriole that can control flow into the bed, but nothing controlling outflow on the other side. In the glomerulus, the capillary bed has an afferent AND an efferent arteriole. The efferent arteriole can also contract, increasing the pressure in the preceding capillary bed.

20
Q

How do you calculate Net Filtration Pressure (NFP)?

A

NFP = (forces favouring filtration - forces opposing filtration)

= P(cap) - P(bc) - Pi(cap)
Because Pi(bc) = 0

Filtration has a positive NFP, reabsorption has a negative NFP.

21
Q

What happens to GFR is NFP is increased?

A

GFR also increases as they are proportional to one another

22
Q

When measuring GFR, what does Kf represent?

A

Filtration Coefficient (Kf)

Function of glomerular capillary, permeability and area available for filtration

23
Q

True or false: Normal GFR is 125 ml/min for a body surface area of 1.73m2

A

True

24
Q

What is a normal Kf value?

A

12.5 ml/min/mmHg

25
Q

What factors affect GFR?

A

Filtration coefficient (Kf)

Capillary hydrostatic pressure

Capillary colloid (oncotic) pressure

Bowman’s capsule hydrostatic pressure

Bowman’s capsule oncotic pressure

26
Q

What is the average renal plasma flow?

A) 1.1 L/min
B) 600 ml/min
C) 75 ml/min
D) 10 ml/min

A

B) 600 ml/min

Renal blood flow is 1.1 L/min but only 600 ml is filterable (the remainder is cells). Therefore, the renal plasma flow (RPF) is 600 ml/min

27
Q

True or false: Only 20% if renal plasma flow is filtered in the nephron

A

True

Renal plasma flow is 600 ml/min, but GFR us 125 ml/min. Therefore 80% of renal plasma flow remains unfiltered

28
Q

True or false: Renal blood flow and GFR are regulated by autoregulation

A

True

RBF and GFR remain constant throughout normal range of BPs, even in isolated kidneys in the lab. Therefore, RBF and GFR must be regulated by the kidney itself (autoregulation)

29
Q

In regulation of renal blood flow, how would constriction of the efferent arteriole affect RBF and GFR?

A

Constriction = ↑resistance in efferent art.

↓RBF ↑GFR

30
Q

In regulation of renal blood flow, how would dilation of the afferent arteriole affect RBF and GFR?

A

Dilation = ↓resistance in afferent art.

↑RBF ↑GFR

31
Q

In regulation of renal blood flow, how would constriction of the afferent arteriole affect RBF and GFR?

A

Constriction = ↑resistance in afferent art.

↓RBF ↓GFR

32
Q

In regulation of renal blood flow, how would dilation of the efferent arteriole affect RBF and GFR?

A

Dilation = ↓resistance in efferent art.

↑RBF ↓GFR

33
Q

True or false: If RBF and GFR change in opposite directions (one ↑ while the other ↓), the resistance has changed in the efferent arteriole

A

True

34
Q

True or false: If RBF and GFR change in the same direction (both ↑ or both ↓), the resistance has changed in the efferent arteriole

A

False

If both change in the same direction, it is the afferent arteriole that has altered resistance

35
Q

What is the name of the structure that forms the contact between the distal tubule and the afferent arteriole?

A

Juxtaglomerular apparatus

36
Q

What is the name of the structure that forms the contact between the distal tubule and the efferent arteriole?

A

Juxtaglomerular apparatus

37
Q

How is GFR controlled by juxtaglomerular apparatus?

A

↑GFR = ↑NaCl and fluid flow in distal tubule

This is detected by macula densa

Macula densa responds by inhibiting NO secretion

↓NO = vasoconstriction of afferent arteriole = ↓GFR

GFR returns to normal, normal flow of NaCL and fluid in distal tubule.

38
Q

Concentrations of NaCl and fluids in the distal tubule are monitored by:

A) Podocytes
B) Juxtaglomerular cells
C) Macula densa
D) Pedicels

A

C) Macula densa

39
Q

Tubuloglomerular feedback occurs in which region?

A

Juxtaglomerular apparatus

40
Q

How does exercise affect renal blood flow and glomerular filtration rate?

A

Increases sympathetic stimulation to afferent arteriole, causing vasoconstriction.

↓RBF ↓GFR

41
Q

The innervation to the kidney is:

A) Rich in sympathetic innervation
B) Rich in parasympathetic innervation
C) Both A and B
D) Neither A nor B

A

A) Rich in sympathetic innervation

42
Q

True or false: Denervation of a kidney (e.g. transplantation) has little effect on its ability to function

A

True

Cardiovascular, Respiratory and Renal Systems (33 decks)

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