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Phase 1 Medicine (JA) > Renal Phys > Flashcards

Renal Phys Flashcards

1
Q

When urine leaves the medulla, name the structures by which urine leaves the kidney.

A

Medulla > Minor calyx > major calyx > renal pelvis > ureter

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2
Q

Name the journey of a blood cell the abdominal aorta towards the nephron.

A

1) Renal artery
2) Segmental artery
3) Interlobar artery
4) Arcuate artery
5) Coronal radiate artery
6) Afferent arteriole
7) Glomerulus
8) Efferent arteriole
9) Peritubular capillaries

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3
Q

What are the capillaries that enter the medulla from the arcuate artery?

A

Vasa Recta

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4
Q

Which cells can be found within the afferent arterioles?

A

Juxtaglomerular cells

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5
Q

Which cells can be found within the DCT?

A

Macula densa

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6
Q

What is the glomerular filtration rate, and how much is this, and what 3 factors affect GFR?

A

The plasma volume that passes from the glomerulus to the bowman’s capsule per minute. 125 ml/min (180L/day)

1) NFP
2) Surface area of glomerulus
3) Permeability of glomerulus

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7
Q

What is renal clearance relative to and why?

A

Inulin clearance. Because it is freely filtered by the glomerulus, and not secreted or reabsorbed in the tubules.

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8
Q

What percent of cardiac output is found in renal blood flow, and what is this value?

A

20%. 1200 ml/min.

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9
Q

How is renal blood flow measured?

A

Renal plasma flow/(1-hematocrit) = 1200 ml/min

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10
Q

What is glomerular hydrostatic pressure?

A

Pressure within the capillary in the glomerulus that is trying to force the filtrate into the bowman’s space (55 mmHg)

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11
Q

What is the colloid oncotic pressure?

A

The pressure of plasma proteins to drag water towards it, e.g. albumin. 30 mmHg.

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12
Q

What is bowman’s capsule hydrostatic pressure?

A

The pressure generate when too much filtrate is in the bowman’s capsule causes a back pressure force toward the glomerulus. 15 mmHg.

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13
Q

What is net filtration pressure?

A

(Glomerular hydrostatic pressure + Capsule osmotic pressure) - (Colloid oncotic pressure + Capsular hydrostatic pressure) = 10 mmHg

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14
Q

What is the relationship between GFR and NFP?

A

Increase in GFP is proportional to the increase in NFP

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15
Q

What does the permeability of the glomerulus and the surface area of the glomerulus create?

A

KF - Filtration coefficient

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16
Q

What is an equation for GFR?

A

NFP x KF

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17
Q

Name two renal intrinsic feedback mechanisms of GFR autoregulation, and what do they respond to?

A

1) Myogenic reflex (systemic BP)

2) Tubuloglomerular reflex (GFR)

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18
Q

How does the myogenic autoregulation mechanism regulate GFR in the afferent arteriole in response to high BP?

A

1) Causes stretch in the smooth muscle
2) Depolarises the smooth muscle
3) Vasoconstriction of the arteriole
4) Reduction in blood flow to glomerulus
5) Lowers GFR

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19
Q

How does the myogenic autoregulation mechanism regulate GFR in the afferent arteriole in response to low BP?

A

1) No stretch dectected
2) Causes the smooth cells to relax
3) Increases the blood flow through the glomerulus
4) Increases GFR

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20
Q

How does the tubuloglomerular reflex autoregulate high GFR?

A

1) High GFR = high NaCl in filtrate
2) High NaCl detected by the macula densa (DCT)
3) Macule densa releases adenosine into the afferent arteriole
4) Adenosine stimulates mesangial cells to release Ca2+
5) causes smooth muscles in the afferent arteriole to constrict
6) Lowers GHP and Lowers GFR

21
Q

How does the tubuloglomerular reflex autoregulate low GFR?

A

1) Low GFR = low NaCl in filtrate
2) Low NaCl detected by macula densa
3) Macula densa does not secrete adenosine, but will secrete NO and PGE2 to vasodilate the afferent arteriole
4) JG cells continue to secrete renin
5) Angiotensin II cause vasoconstriction of efferent arteriole and increases GFR

22
Q

What is the fluid osmolality in the glomerulus and the proximal convoluted tubule?

A

300 mosmols

23
Q

What 3 things are completely reabsorbed in the PCT?

A

1) Glucose
2) Lactate
3) Amino acids
(all set up with Na+/K+ ATPase, all contransported with Na+)

24
Q

How much bicarbonate is reabsorbed in the PCT?

A

90%. Co2 enters the PCT via the blood and gets converted into H+ and HcO3-. H+ enters the lumen and combines with H+ ions to create Co2 and H2O. HCO3- created in the PCT is then ejected into the blood again.

25
Q

How much sodium and potassium is reabsorbed in the PCT?

A

65%. Obligatory water reabsorption dictates that 65% H2O is also reabsorbed.

26
Q

What is the descending limb of the loop of Henle permeable to, and via which channel?

A

H2O. Aquaporin 1.

27
Q

How much of the filtered H2O is reabsorbed in the descending limb?

A

20%

28
Q

Where is the osmolality of the filtrate highest in the loop of Henle?

A

At the tip/bottom (1200 mosmol)

29
Q

What is the ascending limb highly impermeable to?

A

H2O

30
Q

How much K+ Na+ and Cl- is reabsorbed in the ascending limb, and via which channel?

A

~25%. Via the Na+/K+/2Cl- transporter.

31
Q

What is the process by which the loop of henle produces concentrated urine?

A

Counter current multiplier mechanism

32
Q

What is the counter current exchange?

A

Occurs in the vasa recta. Maintains the medullary interstitial gradient, and rpeventing the removal of NaCl, to allow the counter current multiplier to concentrate urine.

33
Q

How does the counter current exchange work in the vasa recta?

A

1) Osmolality in the medulla interstitium is higher at the tip of the loop of henle
2) In the descending vasa recta, H2O is dragged into the interstiium and NaCl is taken up.
3) In the ascending limb, H2O is taken in and NaCl is pushed back out.
This maintains the gradient within the medulla and prevents NaCl being lost.

34
Q

How is calcium and magnesium pulled into the medullary interstitium from the ascending limb?

A

K+ is retained in the ascending limb and depolarises the ascending limb. Calcium and magnesium are reabsorbed via paracellular filtration.

35
Q

What is furosemide, and how does it act?

A

A loop diuretic. Inhibits the Na+/K+/2Cl- transporters in the thick ascending limb which will keep Na, K, and Cl in the urine. This will prevent H20 from being reabsorbed in the descending limb, causing more H2O to be lost in the urine.

36
Q

How much Na and H20 is remaining as the filtrate gets to the early DCT?

A

10% Na

20% H2O

37
Q

How is Na and Cl reabsorbed in the early DCT, and how much Na is reabsorbed at this point?

A

Na+/K+ ATPase creates a gradient. Na+/Cl- symporter takes in Na+ and Cl- from the filtrate to be reabsorbed.. Approximately 5% Na+ is reabsorbed here.

38
Q

How is Ca2+ reabsorbed in the early DCT?

A

PTH. PTH stimulates cells of the early DCT to reabsorb Ca2+ from the filtrate. A Na+/Ca2+ antiporter will then reabsorb in the blood.

39
Q

Where do thiazide diuretics works? Give an example?

A

They work by inhibiting the Na+/Cl- symporter in the the early DCT. Bendroflumethiazide.

40
Q

What is aldosterone stimulated in response to, and what does it do in response?

A

Secreted from the zona glomerulosa of the adrenal glands in response to:
1) Angiotensin II (and low BP)
2) Hyponatraemia
3) Hyperkalaemia
Which stimulate the cells of the late DCT to produce Na+/K+ ATPase on the basal side, and Na+ and K+ transporters on the apical side.

41
Q

Which cells in the late DCT are sensitive to aldosterone?

A

Principle cells

42
Q

Name two examples of a K+ sparing diuretic and where they act.

A

1) Amiloride - Epithelial Na+ channel blocker (ENaC)

2) Spironolactone - Aldosterone antagonist

43
Q

Where is vasopressin secreted from and how does it work in the late DCT?

A

DCT is impermeable to water. ADH will stimulate aquaporins in the epithelial cells to bring water into the blood. Water will follow the movement of Na+.

44
Q

How do intercalated A cells in the collecting duct work when there is acidosis?

A

1) High CO2 in the blood enters cell
2) Gets converted to H+ and HCO3- via CA
3) H+ with K+ (H+/K+ ATPase) secreted into lumen
4) HCO3- reabsorbed into blood to buffer acidosis (H+/Cl- antiporter)
5) Ammonia secreted into the lumen, combines with H+ to create ammonium

45
Q

How do intercalated B cells in the collecting duct work when there is alkalosis?

A

1) High pH in the blood
2) CO2 + H2O = H+ and HCO3-
3) HCO3- is secreted in exchange for Cl- (HCO3-/Cl- antiporter)
4) H+ ions are reabsorbed into the blood in exchange for K+ (H+/K+ ATPase)
5) Decreases the pH in the blood

46
Q

Which cells in the late DCT and collecting duct does ADH work on and how?

A

1) ADH secreted in response to high plasma osmolality, and angiotensin II
2) ADH stimulates principle cells to increase aquaporin 2 on the luminal surface to reabsorb water
3) AQP3 and 4 then releases it in the blood
4) brings osmolality down and increases blood pressure

47
Q

How do Conn’s syndrome and Addisons disease affect potassium levels in the blood?

A

1) Conn’s syndrome - produces too much aldosterone which will act to secrete more potassium. Will cause hypokalaemia
2) Addison’s disease - produced too little aldosterone. Not much K+ is being secreted and stays in the blood, causing hyperkalaemia

48
Q

How does acidosis and alkalosis affect potassium levels in the blood?

A

1) Acidosis - too much H+ in the blood. H+/K+ exchanger will allow H+ to leave the blood in exchange for K+. causes Hyperkalaemia
2) Alkalosis - Too little H+ in the blood. H+/K+ exchanger will allow H+ to enter the blood in exchange for K+. Causes hypokalaemia.

Phase 1 Medicine (JA) (8 decks)

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