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PPP- kidneys Flashcards

1
Q

What products does the kidney produce?

A

renin, vitamin D, erythropoietin, prostaglandins and alpha-klotho

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2
Q

What does the renal corpuscle consist of?

A

glomerulus and bowman’s capsule

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3
Q

What type of endothelium is in the glomerulus capillaries?

A

fenestrated

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4
Q

What are the slit proteins in podocytes?

A

nephrin and podocin

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5
Q

What does the renal tubule drain into?

A

renal pelvis

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6
Q

What are the different types of nephron?

A

cortical - 85%

juxtamedullary - 15%

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7
Q

What is the difference between cortical and juxtamedullary nephrons?

A

cortical are in outer 2/3rds of cortex & have a short loop of henle

Juxtamedullary are in the inner 1/3rd & have a long loop of henle

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8
Q

What are the contents of the juxtamglomerular apparatus?

A
  • Juxtaglomerular cells
  • macula densa cells
  • mesangial cells
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9
Q

What is the vasa recta

A

capillaries that run parallel to the loop of henle

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10
Q

How do you calculate the amount of a substance in urine?

A

amount filtered + amount secreted - amount reabsorbed

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11
Q

Name a substance that is filtered and secreted but not reabsorbed?

A

PAH

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12
Q

Name a substance that is filtered and partially reabsorbed?

A

water and electrolytes

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13
Q

Name a substance that is filtered and completely reabsorbed?

A

glucose

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14
Q

What substance isn’t freely filtered in the glomerulus?

A

proteins

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15
Q

What does glomerular filtration depend on?

A

molecular size and charge

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16
Q

What would a plasma:filtrate ratio of 1 mean?

A

the substance is freely filtered

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17
Q

How does charge affect filtration?

A

basement membrane is negatively charged, so attracts cations

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18
Q

What can cause proteinuria, haemogloinuria and haematuria?

A

infection, glomerulus damage and very high BP

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19
Q

What does GFR mean?

A

the volume of fluid filtered per minute

- ml/min

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20
Q

What is the normal GFR?

A

125ml/min

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21
Q

What does GFR depend on?

A
  • starling forces
  • surface area
  • hydraulic permeability of capillaries
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22
Q

What is the net pressure in the glomerulus due to starling forces?

A

16mmHg

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23
Q

What are starling forces?

A

opposing hydrostatic and oncotic pressure

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24
Q

How can surface area of the glomerulus be controlled?

A

mesangial cells contains actin which is contracted in low BP to reduces SA -> reduces GFR

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25
What effect does constricting afferent arteriols or dilating efferent arterioles have?
reduces GFR
26
What is the normal urine output?
1.5L/day
27
What features does the proximal tubule have for reabsorption?
- brush border - folds in epithelium - lots of mitochondria
28
Where does most reabsorption occur?
in the proximal tubule
29
How is glucose reabsorbed?
- energy comes from Na/K pump - Glucose enters cell via Na co-transport - enters lumen via GLUT transporters
30
What is the renal threshold for glucose filtration?
plasma conc of 200mg
31
What happens if glucose conc is above the renal threshold?
no more glucose is reabsorbed as all the Na co-transporters are saturated
32
How are amino acids rebsorbed?
in the proximal tubule by specific transporters - 8 different types - 6 are Na+ dependent
33
How are acids/anions secreted?
1. enter cells in exchange for DC- via OAT1/3 | 2 enter lumen via ATP-dependent transporters
34
What are some secreted acids/anions?
bile salts, fatty acids, prostaglandins, drugs, PAH
35
How are bases/cations secreted in the proximal tubule?
1. enter cell via OCT2 facilitated diffusion | 2. enter lumen in exchanged for H+ via MATE antiporters
36
What are some secreted bases/cations?
creatinine, dopamine, choline, adrenaline, histamine, atropine, morphine, cimetidine
37
What is the formula for renal clearance?
(U.V)/P
38
What is renal clearance?
volume of plasma cleared of a substance in a given time
39
Why is inulin used to measure clearance experimentally?
- exogenous - not absorbed or secreted - not metabolised - easily measured
40
What is used to measure clearance clinically?
creatinine
41
what does a clearance of >120ml/min indicate?
the substance is secreted
42
what does a clearance of <120ml/min indicate?
the substance is reabsorbed
43
What is the effective renal plasma flow?
600ml/min
44
what is renal blood flow?
600/0.55 = 1100ml/min | - 25% of CO
45
how do you calculate renal blood flow?
plasma flow/1-haematocrit
46
What is the osmolality of plasma?
285-295mosm/L
47
What is the osmolality of urine?
50-1400 mosm/L
48
What is the main osmotically active solute?
Na+
49
Where does sodium reabsorption occur?
mainly in proximal tubule and thick ascending limb - passive in thin ascending - none in descending limb
50
How is sodium reabsorbed in the proximal tubule?
via Na-H+ exchanger and Na-glucose symporter
51
How is sodium reabsorbed in the thick ascending limb?
NKCC transporter | - creates positive charge in lumen -> paracellular cation movement
52
How is sodium reabsorbed in the distal tubule?
Na-Cl cotransporter
53
How is sodium reabsorbed in the collecting duct?
ENaC channel
54
How is urea recycled by the kidneys?
1. passive reabsorption in proximal tubule -> 50% of original 2. secreted by UT-A2 in LOH -> 110% of original 3. reabsorbed by UT-A1 in collecting ducts -> 40% of original
55
How does ADH control water reabsorption?
binds basolateral V2 receptors causes insertion of AQA-2 on luminal side Water moves out of cell by constitutively active AQP3/4
56
How is ADH released?
released from posterior pituitary when plasma osmolality is increased (dehydration)
57
Where are the osmoreceptors that signal ADH release?
hypothalamus
58
What 2 factors maintains plasma osmolality?
urine formation and thirst
59
What is the obligatory water loss per day?
0.4L
60
What is oliguria?
when urine output is less than the obligatory water loss
61
What is the max urine output?
23L/day
62
How is osmolar clearance calculated?
(Uosm x V)/Posm
63
What is osmolar clearance?
the clearance of all osmotically active particles
64
what is the fasting osmolar clearance?
2-3ml/min
65
How do you calculated free water clearance?
V - (Uosm x V)/Posm
66
What are the values of free water clearance?
``` >0 = dilute urine 0 = isosmotic urine <0 = concentrated urine ```
67
What is the main control of ADH secretion?
osmolality
68
What factors can control ADH?
- osmolality (main) - blood volume/pressure (requires greater change) - Alcohol inhibits release - nicotine, pain and stress increase release
69
What is diabetes insipidus characterised by?
polyuria, polydipsia and nocturia
70
What are the 2 types of diabetes insipidus?
neurogenic and nephrogenic
71
What can cause neurogenic diabetes insipidus?
- no secretion of ADH | - congenital or by brain injury
72
What can cause nephrogenic diabetes insipidus?
- inherited mutation e.g. V2 receptor | - acquired by infection or lithium use
73
What is osmotic diuresis characterised by?
polyuria and polydipsia
74
What causes osmotic diuresis?
- increased blood glucose - increases filtrate osmolarity - decreased water absorption in PT, later parts can't compensate
75
How is potassium levels maintained?
- renal excretion - GI losses - cellular shifts
76
How is K+ reabsorbed?
- passivly in PT (65%) - by NKCC2 in thick ascending limb - K-H+ exchange in distal tubule - secreted in principle cells by ROMK and BK
77
What factors affect principle cell K+ secretion?
- ENaC factors - aldosterone (increases secretion) - tubular flow rate (rate increases secretion) - acidosis decreases secretion alkalosis increases secretion
78
What are the concentrations of potassium in hypokalemia?
``` mild = 3-3.5mM moderate = 2.5-3 mM severe = <2.5mM ```
79
What can cause hypokalemia?
- increased external loses - redistribution into cells - low intake
80
What causes increased external loss of potassium?
diuretics, transporter mutations, hyperaldosteronism, alklaosis, vomitting, diarrhoea, skin burns, osmotic diuresis
81
What causes redistribution of potassium into cells?
insulin excess and metabolic alkalosis
82
What happens to the RMP in hypokalemia?
becomes more negative, so takes more to drive to threshold, and repolarises more slowly
83
What concentration indicates hyperkalemia?
Plasma [K+] > 5.5mM
84
What causes decreased external loss of potassium?
renal failure hypoaldosterone drugs
85
What causes redistribution of potassium out of cells?
acidosis cell lysis tissue destruction
86
What happens to the RMP in hyperkalemia?
increased, so more likely to depolarise
87
Is polyuria seen in hyperkalemia or hypokalemia?
hypokalemia
88
What is the treatment for hypokalemia?
- Potassium rich foods - administration of KCl - use of K+ sparing diuretics - alkalosis correction
89
What is the treatment for hyperkalemia?
short term: stabilise heart with Ca2+ medium term: insulin treatment to shift K+ into cells long term: increase excretion with diuretics

FBS1 (9 decks)

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