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Semester 4 (NME) > Kidneys > Flashcards

Kidneys Flashcards

1
Q

What does fenestrated mean?

A

Large pores in endothelium (like in glomerular capillaries)

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2
Q

Which type of nephron is responsible for making concentrated urine?

A

Juxtamedullary

Their long limbs into medulla can create high solute concentrations in peritubular fluid

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3
Q

Where are NKCC2 cells found?

A

Na-K-Cl cotransporter cells

Found only in the thick ascending loop of Henle

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4
Q

What % of glucose should a normal healthy kidney reabsorb?

A

100%

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5
Q

What are the osmolarity differences between the top and bottom of the loop of Henle?

A

Top: 300 mOsm/L
Bottom: 1200 mOsm/L

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6
Q

What is the role of ROMK channels?

A

Move potassium back into urine

K channels

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7
Q

What % of K+ within the body is inside cells? Where is it excreted?

A

98% found inside cells
8% lost from the colon
92% lost via kidneys

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8
Q

How is calcium reabsorbed in the kidney?

A

91%- Prox conv tubule/ loop Henle via paracellular route

6-7%- Distal convoluted tubule via TRPV5 channel

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9
Q

What is the TRPV5 channel?

A

Moves Ca2+ out of urine in dist conv tubule

Responds to levels of PTH/ vitamin D and sex hormones

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10
Q

What are paracellular and transcellular routes?

A

Para- Through interstial spaces beside a cell

Trans- Passes through the cell

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11
Q

What is the role of TRPM6?

A

Moves Mg2+ back into cells (reabsorbes) in distal convoluted tubule

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12
Q

How is magnesium reabsorbed in the kidney?

A

89%- Prox conv tubule/ loop Henle via paracellular route

6-7%- Distal convoluted tubule via TRPM6 channel

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13
Q

Name two factors that can regulate water reabsorbtion and where they act?

A

ADH/ vasopressin (on aquaporin channels)

Aldosterone (on Na reabsorption)

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14
Q

How do glomerular capillaries allow water and small solutes to pass through but not larger ones?

A

Fenestrations between the feet of podocytes allow things to get through
The basement membrane beneath the endothelium stops larger proteins etc from passing through

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15
Q

What is the myogenic stretch reflex (in relation to the kidney)

A

When an arteriole is stretched it automatically contracts (to maintain constant GFR)

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16
Q

What is tubuloglomerular feedback?

A

Distal tubular flow regulates vasoconstriction of afferent arteriole

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17
Q

Which arteriole is most involved in regulating GFR by constricting in response to changes?

A

Afferent arteriole (constricts to lower GFR)

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18
Q

What are the two cell types in the kidney collecting ducts?

A

Principal cells- Mediate sodium and potassium

Intercalated cells- Regulate acid-base homeostasis (also swapping K+)

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19
Q

What is the effect of aldosterone on principal cells in the collecting ducts?

A

Aldosterone increases no of sodium/potassium ATPase pump (so more sodium in, more potassium out)

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20
Q

What is the effect of ADH on principal cells in the collecting ducts?

A

Increases number of aquaporin channels

Increased water reabsorbtion

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21
Q

What is the action of aldosterone in the kidney?

A

Acts on prinicipal cells to increase sodium (and therefore water) reabsorbtion

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22
Q

What would increased aldosterone levels do to the concentration of potassium in urine?

A 
Increase it
(Aldosterone promotes K+ secretion)
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23
Q

What would a decrease in Na+ within the filtrate do to the pH of the tubular fluid?

A

Increase

Fewer hydrogen ions in as they come in cotransported with Na+

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24
Q

How would a lack of juxtamedullary nephrons affect urine concentration?

A

You would be unable to create concentrated urine

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25
Q

What would a decreased Na+ level in the DCT do to blood pressure?

A

Increase it

Macula densa detects low osmolarity then stimulates renin release from JG cells

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26
Q

Where is the majority of HCO3- reabsorbed? How much comes out in urine?

A

80% in proximal convoulted tubule

Less than 0.01% is lost

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27
Q

What is the AE2 transporter?

A

Cl- and HCO3- antiporter

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28
Q

Where would V-ATPase be found?

A

Apical membrane of intercalated cells (H+ pump)

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29
Q

What are the apical and basolateral membranes?

A

Apical: Side towards the lumen
Basolateral: Side towards base

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30
Q

What is Proximal renal tubular acidosis (RTA)?

A

Impaired ability to reabsorb HCO3-
Rare autosomal-recessive disease
NOT treatable by HCO3- supplimentation

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31
Q

What is Distal renal tubular acidosis (dRTA)?

A

Impaired ability to acidify urine

Treatable by HCO3- supplementation

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32
Q

What is the function of the NKCC1 channel?

A

Cotransport of 2Cl-, 1Na+, 1NH4+

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33
Q

What is the function of the ROMK2 channel?

A

Absorbtion NH4+

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34
Q

What are the two ways H+ is secreted in the kidney?

A

As titrateable acid (filtered)

As NH4+ (synthesised)

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35
Q

Which channels are most involved in H+ secretion?

A

NHE3
V-ATPase
H+/K+-ATPase

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36
Q

Which two channels are most important in replenishing plasma HCO3- from kidney reabsorbtion?

A

Basolateral HCO3- exit via:
kNBCe1
AE2

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37
Q

What is a PAK transplant?

A

Pancreas after Kidney Transplant
P first receives a kidney transplant from a living or deceased donor. This is then followed by a pancreas transplant from a deceased donor.

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38
Q

What is a PAT transplant?

A

Pancreas Alone Transplant
This is a treatment for patients with very poorly controlled type 1 diabetes who have hypoglycaemic attacks without warning, and which may threaten their life.

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39
Q

What is the outlook for SPK transplants?

A

90% still function at 1yr

50% at 10yrs

40
Q

What are the exclusion criteria for SPK transplants?

A

T2DM (only type 1 can receive as T2 is resistant)
Malignancy
Chronic infection
Not compliant with treatment

41
Q

What are the main causes of chronic renal failure?

A

Hypertension
Diabetes
Pyelonephritis / glomerulonephritis

42
Q

What causes itching in CKD?

A

High levels of urea

43
Q

What is shown by raised creatinine?

A

Marked damage to functioning nephrons

44
Q

What is the alternative name for a urea test?

A

BUN (Blood urea nitrogen test)

45
Q

What two non-disease factors can affect urea levels?

A

Age= increased urea
High protein diet= Increased urea
Low protein diet= Decreased urea

46
Q

Ureters are retroperitoneal. T or F?

A

True

47
Q

Why do F tend to have more UTI’s than males?

A

Shorter urethra’s

48
Q

What effect would a high protein diet have on the composition of urine?

A

Urea comes from metabolism of AA’s
Therefore urine will contain a higher conc of urea
There may also be increased urine vol (to flush more urea out)

49
Q

What is the main muscle you need to be able to control in order to control the micturation reflex?

A

External urethral sphincter

ring of skeletal muscle formed by urogenital diaphragm

50
Q

Glomerular capillary membranes have what 3 layers?

A

Endothelium- Perforated by fenestrae
Basement membrane- Collagen mesh with spaces to allow water and small solutes to filter
Podocyte layer- With gaps between feet to allow fluid in

51
Q

How does the glomerular capillary use charge to prevent movement of large proteins?

A

Fenestae in endothelium, proteoglycans in BM and podocytes all have -ve charge so help repel proteins

52
Q

What effect does SNS activation have on GFR?

A

Decreases GFR

As SNS causes constriction of renal arterioles, this decreases blood flow

53
Q

What effect does angiotensin II have on GFR and kidney arterioles?

A

Constricts efferent arteriole

This reduces blood flow (and therefore GFR) but raises glomerular hydrostatic pressure

54
Q

What does the juxtaglomerular complex consist of?

A

Juxtaglomerular cells and macula densa cells

55
Q

How do macula densa cells help regulate GFR?

A

MD cells detect NaCl composition to distal tubule, if GFR is decreased, movement is slowed, reabsorbtion of electrolytes increases and tubual fluid has low osmolarity. When they detect this MD cells stim dilation of afferent arteriole + stim JG cells to release renin

56
Q

How do macula densa cells stimulate juxtaglomerular cells?

A

They release prostaglandins which cause JG cells to release renin (JG cells can also use baroreceptors to release renin independantly)

57
Q

What effect does a reduced blood pressure have on GFR?

A

Lowered BP = lowered peritubular capillary pressure = lower capillary hydrostatic pressure = decreased GFR

58
Q

What effect does lowered GFR have on urine concentration?

A

Low osmolarity in urine and it’s passing slower through the tubular system allowing more absorption

59
Q

What is myogenic autoregulation?

A

BV’s respond to stretch or increased wall tension by contraction of vascular smooth muscle
(Stretch allows increased movement of calcium ions into the cells)

60
Q

What effect does a high protein diet have on GFR?

A

Increased AA’s in blood, increased AA reabsorbtion which also increases Na reabsorbtion. This lowers Na at macula densa so increased GFR (makes sense as you want to clear more urea if eating more protein)

61
Q

Why is PAH (para-aminohippuric acid) used to calculate renal plasma flow?

A

Secreted so rapidly that you can clear 90% of PAH from plasma into the urine

62
Q

Glucosuria is an important clinical sign for what?

It begins around what serum glucose level?

A

Diabetes mellitus

Starts at plasma conc around 160-200mg/dL

63
Q

How is the solubility of water changed in the ascending and descending loops of Henle?

A

Descending loop- Very permeable to water

Ascending loop- Virtually impermeable to water

64
Q

How is the solubility of water changed in the ascending and descending loops of Henle?

A

Descending loop- Very permeable to water

Ascending loop- Virtually impermeable to water

65
Q

The permeability of the late distal tubule and cortical collecting duct to water is controlled by concentration of what?

A

ADH

66
Q

What are the two main components which contribute to creating concentrated urine?

A

High levels of ADH

High osmolarity of renal medullary interstitial fluid

67
Q

What is uremia?

A

Raised serum urea level (indicating renal failure)

68
Q

What is prerenal uremia?

A

Caused by decreased perfusion of kidneys with blood

shock, hemorrhage, heart failure

69
Q

What effect does kidney function have on serum potassium?

A

Impaired renal function causes hyperkalaemia

70
Q

What is postrenal uremia?

A

Uremia results from obstruction of tract from renal calyces to urethral orifice

71
Q

What are the classifications of acute renal failure?

A

Depressed excretory function due to reduced GFR. Raised serum urea is classed as pre-renal, renal or post-renal

72
Q

Which region of the nephron reabsorbs 2/3 of Na ions?

A

Prox convoluted tubule

73
Q

Which 3 structures form the filtration membrane?

A

Capillary epithelium, basement membrane, and podocytes

74
Q

Which type of innervation causes micturition?

A

PNS

75
Q

What type of channel is NKCC1 and what does it transport?

A

Cotransporter (Na, K, Cl)

76
Q

Which hormone increases reabsorption of water from the collecting ducts?

A

ADH

77
Q

At what vertebral level are the kidneys found?

A

Left: T11-L2
Right: T12-L3
Right is lower than left due to liver
L kidney is longer and closer to midline

78
Q

Are the kidneys intraperitoneal or retroperitoneal?

A

Retroperitoneal

79
Q

What is at the inferior pole of each kidney?

A

R and L coliec flexures

80
Q

Where would an intercalated cell be found?

A

Collecting ducts

81
Q

What is the role of ATPsynthase enzyme?

A

Uses H+ from ETC to phosporylate ADP creating ATP

uses H+ gradient for energy

82
Q

What dictates whether a nephron is cortical or juxtamedullary?

A

The location of it’s glomerulus

83
Q

When a micturation reflex has occurred but not succeeded what happens?

A

It remains inhibited for a few mins

Then will start again if enough pressure

84
Q

What is the role of the higher brain centres in micturation?

A

Keep the reflex inhibited except for when you want to urinate

85
Q

How is voluntary urination initiated?

A

Person contracts abdo muscles (increases pressure on bladder which stimulates stretch receptors)

86
Q

What is tuberoglomerular feedback?

A

Macula densa monitors Na+ conc and when it’s low sends a signal to the afferent arteriole to relax (and therefore increase GFR)

87
Q

What effect does a lowered GFR have on the Na+ concentration in the tubule?

A

Low GFR = slower movement = more time for reabsorption = lower Na+ conc in tubule
(So macula densa will stimulate GFR increase)

88
Q

What is myogenic autoregulation?

A

BV’s respond to increased tension by contracting

Stretch of the wall allows increased movement of Ca2+ causing the contraction

89
Q

What does high protein intake do to GFR?

A

Increases AA’s which are reabsorbed in the PCT and also stimulate Na+ reabsorption. Lower Na+ stimulates a raise in GFR

90
Q

What is glomerulotubular balance?

A

The ability of the tubules to increase their reabsorption rate in response to increased tubular load (increased tubular inflow)

91
Q

What effect does increases renin release do to GFR?

A

Increased renin = increased angiotensin II = constriction of efferent arterioles = reduced blood flow = increased GFR

92
Q

What is the difference between alpha and beta intercalated cells in the collecting ducts?

A

Alpha- Secretes H+ and reabsorbs bicarbonate

Beta- Secretes bicarbonate and reabsorbs H+

93
Q

What is filtration fraction (FF)?

A

The proportion of the fluid reaching the kidneys which passes into the renal tubules.
Normally about 20%
Ratio of GFR to RPF (renal plasma flow)

94
Q

What equation is used to work out filtration fraction?

A

FF = GFR/RPF

95
Q

What are mesangial cells and what sort of molecules stimulate them (3)?

A

Support cells which can constrict/ dilate BV’s

- Target for angiotensin II/ ADH and histamine

Semester 4 (NME) (24 decks)

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