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Renal > Renal physiology > Flashcards

Renal physiology Flashcards

1
Q

What are the 2 types of kidney nephrons

A

Cortical nephrons (70-80%)
Juxtamedullary nephrons (20-30%)

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2
Q

Cortical Nephrons

A

Glomeruli in outer cortex
Short-looped

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3
Q

Juxtamedullary nephrons (20-30%)

A

Glomeruli border on medulla
Long-looped
Paired with extensive vasa recta (specialised blood supply)

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4
Q

Renal Blood flow (RBF)

A

Renal blood flow (RBF) ~20% of cardiac output/min

𝑹𝑩𝑭=𝑹𝑷𝑭/(πŸβˆ’π’‰π’‚π’†π’Žπ’π’„π’“π’Šπ’•)
E.g
𝑹𝑩𝑭=πŸ”πŸ“πŸŽ/((πŸβˆ’πŸŽ.πŸ’πŸ“)) = 1182 ml/min

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5
Q

What is renal blood flow NOT the same as?

A

Renal plasma flow

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6
Q

Glomerular filtration

A

~ 20% of Renal Plasma Flow

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7
Q

What is GFR related to

A

arterial pressure and capillary properties
Blood enters afferent arteriole with RPF of 650ml/min into glomerulus > GFR ~125 ml/min) > out the efferent ateriole

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8
Q

How many litres of fluid is filtered a day by GFR

A

~180L filtered/day

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9
Q

How much fluid is reabsorbed after GFR

A

~179L reabsorbed

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10
Q

What is GFR influenced by?

A

Net Filtration Pressure (NFP)
Hydrostatic pressures
Colloid osmotic pressures

Renal Blood Flow (RBF)
Autoregulation

Filtration coefficient (Kf; filter integrity/function)
Arteriolar endothelium
Glomerular podocytes
T2DM
Hypertension

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11
Q

Which 4 forces is net fluid movement

A

Glomerular hydrostatic pressure
(GHP; fluid out)

Glomerular colloid osmotic pressure
(pG; protein; fluid in)

Bowman’s Capsule fluid pressure
(BCP; fluid in)

Bowman’s Capsule colloid osmotic pressure (pB; ??)

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12
Q

Net filtration pressure (NFP) equation

A

GHP – (BCP + pG)

NFP = 60 – (18+32)

NFP ~ 10 mm Hg

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13
Q

As you go from the afferent to efferent arteriole what happens to the glomerular colloid osmotic pressure

A

The gradient increases

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14
Q

Glomerular hydrostatic pressure

A

As blood flows through afferent arteriole GHP forces fluid out

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15
Q

What 3 parameters is GHP influenced by

A

Systemic arterial pressure
Tends to increase GHP and GFR
BUT renal auto-regulation minimises major change

Afferent arteriolar resistance
Generally reduces GHP and GFR

Efferent arteriolar resistance
Increased GHP, variable response in GFR (increase then decrease)

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16
Q

What happens with increased resistance of afferent arteriole (constriction of afferent arteriole)

A

Causes Reduced Hydrostatic Pressure +
Reduced GFR in glomerulus
Hydrostatic pressure drops after blood flows through efferent arteriole causing a decrease in flow

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17
Q

What happens with decreased resistance of afferent arteriole (dilation of afferent arteriole)

A

Causes increased Hydrostatic Pressure +
Increased GFR in glomerulus
Causes increased resistance in Efferent arteriole (partially constrict due to Ang II) > causes decreased HP and increased glomerular colloid osmotic pressure which causes increased fluid reabsorption

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18
Q

What happens with decreased resistance of afferent arteriole (dilation of afferent arteriole) Part 2

A

Causes increased Hydrostatic Pressure which causes increased glomerular colloid oncotic pressure
Causes increased resistance in Efferent arteriole (severe constrict > lowers GFR) > causes decreased HP in Efferent arteriole leading to decreased flwo

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19
Q

Renal Auto- regulation:

A

Intrinsic feedback mechanisms
Maintains near constant:
Renal blood flow
GFR

20
Q

What does renal auto-regulation minimise the impact of?

A

systemic arterial pressure variations on RBF & GFR

21
Q

What happens without autoregulation?

A

Large increase in urine output (>40L/day)

Involves:
Afferent and efferent arterioles
Tubuloglomerular Feedback

22
Q

GFR and autoregulation

A

Increased NaCl reabsorption at PCT > decreased NaVl sensed by Macula Densa cells in (DCT) > Autocoid secretion (PGE2, PGI2) > Causes decreased resistance in Afferent arteriole and increased GHP restoring GFR> Also causes release of Renin from juxtaglomerular cells > Causes RAAS > RAAS causes increased efferent arteriole resistance increasing GHP restoring GFR

23
Q

What is the indicator for renal function

A

GFR

24
Q

GFR, creatinine and Renal function

A

Requires plasma creatinine value
Creatinine filtration rate = GFR x [creatinine]plasma
Creatinine excretion rate β‰… creatinine production

25
Q

Early stage renal failure

A

Significant decreased GFR > small increase in [creatinine]plasma

26
Q

What is needed to figure out GFR the indicator of renal function

A

Requires plasma creatinine value:
Clinically use estimated GFR (eGFR)
Doesn’t consider creatinine tubular secretion

27
Q

Drawbacks of GFR

A

Can overestimate GFR due to tubular creatinine secretion (10-15%)
Creatinine metabolism reflection on lean body mass
Ethnic correction removed
Not validated in pregnancy

28
Q

Factors that decrease GFR

A

D= Decreased
I= Increased
D Kf= Renal disease Diabetes mellitus Hypertension
I BCP = Urinary tract obstruction
(kidney stones)
I pG = D RBF, I Plasma proteins
D GHP = D Arterial pressure
D R in Efferent = D ANG II (Due to ACEi/ ARB)
I R in Afferent = NSAIDs

29
Q

Four basic procces of kidney

A

1.Filtration:
Glomerulus
Water and solutes across glomerular capillaries

  1. Reabsorption:
    Water and solutes from tubular filtrate
  2. Secretion:
    Solute from blood and peritubular fluid into tubular fluid
  3. Excretion:
    Into urine
30
Q

Drugs for Kidney

A

Thiazide diuretics
Bendroflumethiazide
-ve Na+/Cl- co-transporter
Loop diuretics Furosemide
-ve Na+-2Cl–K+ ATPase
K+-sparing diuretics (Amiloride – Na+ channel)
(Spironolactone – aldosterone antagonist

31
Q

Late distal and Cortical collecting tubules

A

Sensitive to ADH
Impermeable to urea

32
Q

3 cell types of
Late distal and Cortical collecting tubules

A

Priniciple cells
Type A intercalated cells
Type B intercalated cells

33
Q

Principal cells

A

Sensitive to ALDOSTERONE

Na+ /H2O reabsorption

Key role - K+ secretion

I[K+]ECF > I Aldosterone; I Na+/K+ ATPase

34
Q

Type A intercalated cells

A

Buffer acidosis
H+ secreted
K+ / HCO3- reabsorbed

35
Q

Type B intercalated cells

A

Buffer alkalosis
H+ reabsorbed
K+ / HCO3- secreted

36
Q

Factors that cause increased [K+]ECF

A

Insulin
Hyperaldosteronism
-Conn’s syndrome
-Cushing’s?
b2-agonists
Alkalosis

37
Q

Causes increased [K+]ECF

A

Insulin deficiency
Aldosterone deficiency
-(Addison’s disease)
b2-antagonists
Acidosis
Cell lysis
Exercise
I ECF osmolarity
Diet

38
Q

Regulation of ECF volume: Basic system

A

I BV > I BP > I Renal excretion > Normal vol restored

39
Q

What is the most abundant ECF ion

A

Na

40
Q

What does Sodium determine in ECF?

A

Osmotic pressure (osmolality)
Volume

41
Q

What regulates Blood Pressure and Volume

A

Baroreceptor reflexes (cardiovascular lecture slides)
Negative feedback loops
Short-term, continuous regulation

Renal Involvement
Juxtaglomerular Apparatus
Macula densa (Renin/Angiotensin)
Tubuloglomerular feedback

42
Q

What is a renal response to expansion in ECF volume

A

ANP - Water/NaCl loss

43
Q

ANP - peptide hormone

A

I ECF vol > I atrial stretch > D Hypothalamic ADH synthesis

44
Q

ANP causes Afferent arteriole dilation leading to what?

A

Increased GFR

45
Q

ANP inhibits Renin secretion leading to….

A

Decreased:
Ang II
Aldosterone secretion
Systemic vascular resistance

46
Q

ANP causes decreased DCT Na reabsorption leading to water

A

I Water secretion leading to pressure diuresis > Decreased ECF volume

47
Q

ANP generally antagonises what?

A

Angiotensin II actions

Renal (15 decks)

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