Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Kidney physiology > Role of the kidney > Flashcards

Role of the kidney Flashcards

1
Q

What are the 2 steps of urine formation?

A

Glomerular filtration

Modification of urine (tubular reabsorption and secretion)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are overall functions of kidney?

A

Filter and excrete waste products from blood and urine

Regulate body fluid composition (salt and water)

Endocrine functions (regulate bp via renin, produce erythropoietin in hypoxia, hydroxylate and activate vitamin D3)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the glomerulus?

A

Capillary knot where blood filtered into renal tubules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How many glomeruli are there per kidney?

A

1 million glomeruli, each associated with single renal tubule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What % of total blood volume do the kidneys receive per minute?

A

20%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the renal plasma flow rate?

A

How much plasma passes through kidneys per min - 625ml/min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Roughly what % of plasma is filtered from the blood through each pass through the kidney?

A

20%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the GFR?

A

The volume of blood filtered by the kidneys per minute - 125ml/min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why is the pressure high in the glomerulus, how is pressure changed?

A

Hydrostatic pressure is high (45mHg) for maximum ultrafiltration

Regulated by differential constriction of the afferent and efferent arterioles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What type of capillary wall does the glomerulus have?

A

Fenestrated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What structure allows tuberuloglomerular feedback?

A

Macula Densa: Ascending limb meets DCT, sits next to afferent arteriole of same tubule - feedback mechanism to regulate GFR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe distribution of vascular pressure along renal vasculature

A

Highest at renal artery, dips to afferent arterioles, then large dip to efferent and then steady decrease along peritubular capillary to intrarenal vein and renal vein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is high pressure generated in glomerulus?

A

Afferent arterioles wider than efferent so high hydrostatic pressure (45mmHg) in capillaries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How is glomerulus adapted to function?

A

Capillary knot large, for large SA

Afferent arteriole wider than efferent

Filtration barrier allows ions water and small solutes to filter out of blood: filters base on size charge and shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Compare composition of filtrate in renal corpuscle and plasma

A

Same but lacks protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What three layers must filtrate pass through?

A
  1. Endothelial cells of fenestrated capillary (60nm)
  2. The endothelial basement membrane
  3. The epithelial layer of podocytes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How does filtrate pass out of capillary endothelium?

A

Holes in cytoplasm due to doughnut cellular arrangement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How does glomerulus filter based on size?

A

Fenestrated endothelial cells 60nm diameter fenestrations block cell passage

Slit pores formed by pedicels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How does glomerulus filter based on charge (2 features)?

A

Fused basement membrane of endothelial cells and podocytes - rich in negatively charged GAGs - barrier to -ve charged macromolecules

Podocytes - have -ve charged nephrins from pedicles which interdigitate to form slit pores - prevent large -ve charge molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What causes Congenital form of nephrotic syndrome

A

Caused by nephrin mutations - pedicles fuse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is adult form of nephrotic syndrome?

A

Damage to basement membrane - proteinuria, oedema and

hypoalbuminaemia

22
Q

How is filtration driven by Starling forces (two promoting, two opposing)?

A

Forces driving filtration:

  • Capillary hydrostatic pressure
  • Osmotic pressure within Bowman’s space

Forces opposing filtration

  • Hydrostatic pressure in Bowman’s space
  • Osmotic pressure in capillary
23
Q

Why is the osmotic pressure in the Bowman’s space negligible?

A

Osmotic pressure driven by proteins (oncotic pressure)

This is small because no proteins should be in filtrate

24
Q

What is net filtration pressure in glomerulius?

A

[HP (cap) + OP (bs)] - [HP (bs) + OP (cap)]

Note: Oncotic pressure in bowman’s space = 0 and HP in bowman’s space is low

25
Q

Equation for GFR

A

Net filtration pressure x Kf (filtration coefficient)

Kf = surface area x permeability
(high SA as capillary + mesingual cells contracting, high permeability due to fenestrations)

26
Q

Why is Kf high?

A

Kf = surface area x permeability

high SA as capillary + mesingual cells contracting, high permeability due to fenestrations

27
Q

What drives filtration?

A

High hydrostatic pressure in capillary

Removal of filtrate to proximal tubule

28
Q

What is the most important factor affecting GFR?

A

Capillary hydrostatic pressure

29
Q

Describe changes in oncotic and hydrostatic pressure as blood is filtered

A

Capillary: HP falls slightly, OP rises as [protein] increases

Bowman’s space: HP low and doesn’t increase, Oncotic pressure/[Protein] basically 0

30
Q

What are mesangial cells?

A

Modified Smooth muscle cells in capillary that regulate SA of capillary (i.e.stretch endothelial cells) for filtration

31
Q

How is GFR regulated?

A

Hydrostatic pressure adjusted to hold GFR steady

Autoregulation

  1. Myogenic
  2. Flow dependent mechanism i.e. tubuloglomerular feedback
32
Q

How do changes in afferent or efferent arteriole diameter change hydrostatic pressure and thus GFR?

A

Constriction of afferent (i.e. resistance increases) decreases HP in glomerulus decrease GFR.

Constriction of efferent increases HP, increase GFR

33
Q

If arterial bp rises, how is GFR held steady by the myogenic mechanism?

A

Increased pressure stretches the arteriole smooth muscle, stretch mediated Ca2+ channels leads to increase in intracellular calcium causing increases contraction.

34
Q

If arterial bp rises, how is GFR held steady by flow dependent mechanism (tubuloglomerular feedback)?

A

Increased GFR increases flow to disrtal nephron, sensed by macula densa (monitors Cl- and Na+ reabsorption) which releases signal (adenosine) to constrict afferent arteriole and inhibit renin release from granular cells in afferent arteriole wall.

35
Q

Apart from intrinsic regulation, how is GFR regulated (2 ways)?

A

Mesangial cells in Bowman’s capsule contract
Alter SA of capillary knot and thus Kf

HP (bowman’s space) may increase if ureter obstructed e.g kidney stones fluid backs up

36
Q

What is renal clearance of a substance, give units?

A

Minimum volume of plasma from which substance has been completely removed and excreted to urine per unit time (ml/min)

37
Q

What are criteria for clearance to be used to estimate GFR?

A

Amount of substance removed from blood = amount appearing in urine,

Only occurs when:

1) Freely filtered
2) not reabsorbed from nephron (otherwise GFR would appear smaller)
3) not secreted into nephron
4) not metabolised/made b kidney

38
Q

What substance can be used to estimate GFR from clearance?

A

Inulin

39
Q

What is the GFR of inulin?

A

125ml/min

40
Q

What is the excretion rate?

A

UxV

Concentration of X in urine (U mmol/ml)

Volume of urine produced per unit time (V ml/min)

41
Q

What is removal rate?

A

PxC

Concentration of X in plasma (P mmol/min)

Volume of plasma cleared per unit time (C ml/min)

42
Q

What is clearance? Equation

A

C = (UxV)/P (assume removal rate=excretion rate)

43
Q

Accurate markers for glomerular filtration rate must be …

A

Passively filtered by the glomerulus.

44
Q

How is GFR measured using the renal clearance of urea affected in antidiuresis, why ?

A

Decreased (urea is excreted from tubule in antidiuresis, removal rate is less than excretion rate)

45
Q

Why does nephrotic syndrome not affect renal clearance of urea?

A

Filtered out anyway

46
Q

How many mg of substance appear in the urine per minute?

A

VxU

47
Q

One endocrine function of the kidney is…

A

vitamin D activation

48
Q

What is the normal GFR in L/day?

A

180 L/day

49
Q

What is the glomerular hydrostatic pressure?

A

60 mmHg

50
Q

What is the glomerular capillary colloid osmotic pressure?

A

32 mmHg

51
Q

What affect on GFR does strong activation of renal sympathetic nerves have?

A

Decreases it

52
Q

Is urea clearance larger, the same or smaller than the glomerular filtration rate?

A

smaller

Kidney physiology (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions