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Human Systems and Anatomy > Kidney Tubular Function > Flashcards

Kidney Tubular Function Flashcards

1
Q

how much filtrate is produced every day in a healthy individual

A

180 litres

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2
Q

what proportion of total daily filtrate is reabsorbed in the renal tubules

A

99%

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3
Q

describe the filtration barriers main function

A

selects molecules to be filtered from blood plasma into the nephron based on their size and charge to form filtrate

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4
Q

how many times a day is the fluid in our body filtered through the kidneys

A

3-4 times a day

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5
Q

what are the components of the renal tubule

A

proximal convoluted tubule
loop of henle
distal convoluted tubule

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6
Q

what is the function of the renal tubule

A

reabsorption and secretion for conserving the water and electrolytes in the body

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7
Q

how much filtrate is immediately reabsorbed through the proximal convoluted tubule

A

two thirds

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8
Q

what does the transport of sodium in the proximal convoluted tubule also facilitate the reabsorptiono f

A

nutrients
water
ions

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9
Q

how much sodium is reabsorbed in the proximal convoluted tubule

A

65%

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10
Q

how much of the sodium in the filtrate is reabsorbed in the ascending loop of henle

A

25%

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11
Q

how much sodium is reabsorbed in the distal convoluted tubule

A

up to 8%, but this value depends on the hormonal regulation

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12
Q

how is sodium reabsorption in the distal convoluted tubule regulated

A

depending on the body’s requirements and therefore it is through hormonal regulation

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13
Q

how much of the sodium in the filtrate is reabsorbed in total

A

around 98%

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14
Q

how much of the kidneys energy requirement is dedicated to the reabsorption of sodium

A

80%

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15
Q

what is the role of proximal convoluted tubule

A

reabsorption and secretion

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16
Q

what is the role of the loop of henle

A

counter current multiplier

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17
Q

what is the role of the distal convoluted tubule

A

reabsorption and secretionw

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18
Q

what is the role of the collecting duct

A

urine collection

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19
Q

what is the function of the renal corpuscle

A

filtration

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20
Q

how is the proximal convoluted tubule designed

A

in order to facilitate its function: it is long, and is convoluted. this means it bends in on itself to maximise surface area for reabsorption

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21
Q

how does the glomerulus appear in the masson trichrome stain

A

black

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22
Q

where are the glomerular capillaries in the kidneys

A

the renal cortex

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23
Q

what are the vasa recta

A

these are the peritubular capillaries that are very closely associated with the nephrons to allow direction of movement of substances from the blood to the tubular lumen and vice versa

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24
Q

what specialisation is present in the epithelial lining of the proximal convoluted tubule

A

microvilli

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25
Q

what type of transport does sodium travel via

A

active transport

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26
Q

is urea reabsorbed

A

yes

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27
Q

is creatinine absorbed

A

no, this is why it is the value used in urine samples to measure the efficiency and health of the kidneys

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28
Q

describe the concentration gradient in the proximal convoluted tubule

A

the filtrate has a high concentration of solutes and water relative to the concentration in the peritubular capillaries.
this is what regulates the passive diffusion in the proximal convoluted, where half of the filtrate is reabsorbed immediately upon entering the proximal convoluted tubule

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29
Q

how many litres of filtrate are absorbed passively due to the laws of physics

A

90%

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30
Q

how is water reabsorption facilitated

A

using pores and carrier proteins to allow for the diffusion

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31
Q

what are aquaporins

A

these are protein pores in the bilayer that allow for free movement of water down its concentration gradient from the lumen across the epithelium into the peritubular capillaries

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32
Q

what is passive diffusion

A

the movement of molecules from high to low concentration until equilibrium is reached

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33
Q

what are the molecules commonly found in filtrate

A

sodium ions
water
chloride ions
glucose
amino acids
urea
creatinine

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34
Q

how do glucose and amion acids move across the apical surface for reabsorption

A

via sodium cotransporters: sodium is pumped and they hitch a ride

35
Q

which molecules are important for facilitating the passive diffusion occurring in the proximal convoluted tubule

A

aquaporins and carrier proteins

36
Q

how much of the filtrate urea can be reabsorbed

A

up to 50%

37
Q

why does creatinine not get reabsorbed

A

it has no transporter protein

38
Q

where are the sodium potassium pumps found in the proximal convoluted tubule

A

on the basolateral membrane

39
Q

why does water follow sodium wherever it goes

A

osmosis

40
Q

how do chloride and other negative ions get reabsorbed

A

they also follow sodium

41
Q

how is sodium reabsorbed into the bloodstream

A

the sodium potassium pump disrupts equilibirum by moving sodium into the interstitial space
this causes an accumulation in the interstital space
as blood flows, the sodium moves down its concentration gradient into the peritubular capillaries

42
Q

how many of the nutrients in the filtrate are reabsorbed

A

up to 100%

43
Q

when might it be the case that not all nutrients are reabsorbed in the kidneys

A

diabetics with an excess of glucose in the blood

44
Q

how many litres reabsorbed immediately

A

120

45
Q

how does water reabsorb

A

follows sodium via osmosis

46
Q

how does chloride reabsorb

A

follows electrical gradient

47
Q

list all that the active transport of sodium facilitates

A
  • nutrient reabsorbtion
  • water reabsorption
  • negative ions follow the electrical gradient
48
Q

does sodium transport affect waste removal

A

no, urea is reabsorbed via passive diffusion and creatinine is not reabsorbed

49
Q

how much remaining filtrate is in the loop of henle

A

60 litres

50
Q

where does the counter current multiplication system occur

A

in the juxtamedullary nephrons

51
Q

what are the sections in the loop of henle

A

thin descending limb
thin ascending limb
thick ascending limb

52
Q

what are the loop rules

A

the idea that each limb in the nephron has different permeability and transport properties

53
Q

what do aquaporins do

A

they allow for free movement of water out of the filtrate

54
Q

which part of the loop of henle has aquaporins

A

the thin descending limb

55
Q

describe the thin descending limbs loop rules

A
  • aquaporins
  • freely permeable to water
  • does not contain active sodium pumps
56
Q

describe the loop rules of the thin ascending limbs

A
  • no aquaporins
  • impermeable to water
57
Q

describe the loop rules of the thick ascending limb

A
  • site of active sodium reabsorption
  • no aquaporins
  • impermeable to water
58
Q

what drug is used to inhibit the action of the NKCC2 pump

A

furosemide

59
Q

what conditions are created in the medulla as sodium is actively reabsorbed from the filtrate

A

it becomes salty as there is an increase in sodium concentration

60
Q

what happens to water in the filtrate as it enters the loop of henle

A

the medulla is salty, so the water wants to follow the sodium and is drawn out from the filtrate into the medulla as well

61
Q

what happens to the concentration of the filtrate as it descends the thin ascending limb

A

it becomes more concentrated as the sodium ions are retained and water diffuses out

62
Q

what is the typical concentration of our bodily fluids

A

300 mini osmoles per litre

63
Q

how does the concentration of the filtrate change as you go from the medulla up through the ascending limbs

A

it decreases because sodium is being pumped out but the water is remaining

64
Q

what is the concentration of sodium ions at the top of the loop of henle

A

around 100 mini osmols

65
Q

what is the importance of the counter current multiplication

A

to save water and sodium from excretion - primary function of the loop of henle is water retention

66
Q

what is the counter current multiplication

A

the mechanism in the loop of henle for water reabsorption
counter current because the filtrate flows in two opposite directions
multipilication because the concentrtion is multiplied as you go deeper into the medulla

67
Q

how do the vasa recta work to ensure the concentration gradient is not washed away

A

the blood flow is slow, and at each level the blood concentration gradient will equalise with the medulla

68
Q

what supports the concentration gradient of the medulla

A

blood flow from the vasa recta

69
Q

what is the function of the distal convoluted tubule

A

site of fluid volume and electrolyte regulation

70
Q

which three hormones are involved in regulating the distal convoluted tubule

A

anti diuretic hormone
aldosterone
atrial natriuretic hormone

71
Q

what does ADH do

A

increase water reabsorption

72
Q

what does aldosterone do

A

increase sodium reabsorption

73
Q

what does ANH do

A

promote sodium secretion

74
Q

what is the by product of the kidneys main function

A

production of urine

75
Q

are there aquaporins in the distal convoluted tubule

A

no

76
Q

is filtrate hypotonic or hypertonic in the absence of hormone regulation

A

hypotonic

77
Q

describe the pathway that ADH follows

A
  • lost fluids detected by a change in blood pressure or increased serum osmorality
  • detected by the pituitary gland which will produce ADH
  • one ADH target is the epithelial lining of the distal convoluted tubule and cells of the collecting duct
  • cells insert aquaporins in the cell membrane
78
Q

describe urine production when ADH acts on the distal convoluted tubule

A

smaller volume, more concentrated

79
Q

what is the vasopressin receptor

A

a cell surface membrane receptor called AVPR2

80
Q

describe how ADH/vasopressin leads to production of aquaporin channels

A

activates a signal transduction pathway in the target cell when it binds to its extracellular receptor
this regulates transcription factors to lead to transcription and translation of proteins
aquaporin channels inserted into the membrane to allow water to flow passively

81
Q

describe the action of aldosterone on the distal convoluted tubule

A

upregulates the activity and insertion of the sodium potassium pumps and channels
steroid hormone so it enters the cell and acts directly on the transcription factors

82
Q

which two hormones work together to increase the internal fluid volume

A

adh and aldosterone

83
Q

describe the action of ANH on the distal convoluted tubule

A

counteracts the effects of ADH and aldosterone to produce large volumes of diluted urine

body gets rid of excess fluid if blood pressure is too high, and acts on the cells in the same place as others

aquaporins are removed from the cell membrane of the sites, and activity of sodium potassium pumps are removed

salt and water are retained in the tubule, and excreted in the body

Human Systems and Anatomy (57 decks)

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