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Genitourinary System > Kidney physiology > Flashcards

Kidney physiology Flashcards

1
Q

what are some examples of problems thatmess with homeostasis of water and electrolytes?

A

-haemorrage
-unusual eating or drinking behaviour
-severe dehydration, rapid fluid loss from the gut or after burns
-unintended consequences of drug actions

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2
Q

what is the water and electrolyte homeostasis?

A

-intake/loss must be in balance

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3
Q

what is the typical input of water?

A

2.5L day
1200ml water
1000ml food
300ml metabolic

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4
Q

what is the typical output of water?

A

2.5L per day
1500ml urine
100ml swear
200ml faeces
700ml insensible loss

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5
Q

what can affect the output of water?

A

temperature
humidity
activity

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6
Q

what happens during periods of heavy exercise or in hot/humid conditions?

A

sweat loss can >2L/hour, >10L/day
urine output reduced in these conditions

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7
Q

what are the daily recommendations of salt?

A

6g/day
3.75g/day if 51 or older or have high BP, diabetes or chronic kidney disease

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8
Q

how much CO goes to kidneys?

A

25% supplies the 200g of tissue
625ml/100g/min

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9
Q

what is the blood pressure in glomerular capillaries?

A

50-60mmHg

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9
Q

how do we achieve high BP in glomerular capillaries?

A

renal artery is short and has a relatively large radius

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10
Q

what are the sequence of blood vessels in the glomerular capillaries?

A

afferent arteriole
glomerular capillaries
efferent arteriole
tubular capillaries
venule

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11
Q

what are the 2 types of nephrons?

A

superficial and juxtamedullary

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12
Q

which type of nephron is water reabsorption more effective?

A

longer jjuxta-medullary nephrons

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13
Q

what are the 4 sections of the nephron?

A

PCT
loop
DCT
collecting duct

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13
Q

what is reabsorption?

A

active pumping from filtrate in tubules
(substances that are retained are water, glucose, amino acids and electrolytes)

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14
Q

what is secretion?

A

active pumping into tubules
for substances to be eliminated faster than filtration alone allows (H+, ammonia, uric acid and some drugs)

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15
Q

what else can affect pumping rates?

A

hormones
eg aldosterone can adjust the rates of Na and K excretion

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16
Q

where does filtration of small molecules and water occur?

A

between podocytes
cut off is 67KD

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17
Q

what are some small molecules that can filter through podocytes?

A

ions, urea, glucose, amino acids and small proteins

18
Q

what is the normal glomerular filtration rate?

A

90-140ml/min

19
Q

what is the brush border?

A

-active resporption of glucose, amino acids, NA and K ions
-co transporters, aqueous channels, membrane pumps
-substantial water reabsorption

20
Q

what has happened by the end of the PCT?

A

-complete reabsorption of glucose and amino acids
-substantial reabsorption of Na and water
volume of filtrate reduced by 2/3rds

21
Q

which wall of the loop of henle is thicker?

A

thinner wall descending into the medulla
thicker wall ascending from the medulla

22
Q

why is the wall ascending thicker?

A

so it can pump the solute up

23
Q

what occurs at the loop of henle?

A

Solute diffuses into descending tubule: Counter-current mechanism ‘recycles’ solutes.
Ion pumping develops high osmotic pressure at the tip of the loop.
No net re-absorption here.

24
Q

what happens in the Distal Convoluted Tubule?

A

Similar structure and function to Proximal Tubule. Compare A and C. No need for glucose transporters
Less intense electrolytes and water re-absorption
DCT ion pumping can be controlled by hormones like aldosterone to ‘fine tune’ Na + and K + exchange

25
Q

what happens in the collecting duct?

A

concentration of urine
CDs pass close to tips of Loop
If CDs are permeable to water, then moves out of the duct to concentrate filtrate.
Duct permeability set by ADH/AVP.
When ADH/AVP is present Aquaporins are inserted into the luminal membrane to allow water movement.
Rapid insertion/removalallows quick responses

26
Q

what is the normal plasma osmolarity?

A

300mOsm

27
Q

what happens when water intake is restricted?

A

When water intake is restricted, plasma osmolarity ↑.
More ADH/AVP is secreted by the hypothalamus.
ADH ↑ the water permeability of Collecting Ducts.
More water is reabsorbed.
Concentrated urine is produced.

28
Q

what is the max conc of urine?

A

1200 mOsm.

29
Q

what is the minimum urine output?

A

1ml/min

30
Q

what happens when excess water is consumed?

A

If excess water is consumed, plasma osmolarity falls
Hypothalamus secretes less ADH/AVP.
Collecting Duct walls loose permeability to water.
Dilute urine is produced.

31
Q

what is the max urine output?

A

20ml/min

32
Q

how is filtration pressure controlled?

A

Hypo-filtration initiates secretion of Renin by the Juxtaglomerular apparatus.
Renin splits Angiotensinogen to makeAngiotensin I which is converted to Angiotensin II a powerful vasoconstrictor.
This system regulates renal blood flowand glomerular filtration rate (low BP, low renal flow, hypofiltration, etc)

33
Q

what enhances the system that increases BP?

A

sympathetic NS

34
Q

where is renin released from?

A

juxtaglomerular cells

35
Q

what is angiotensin II a?

A

a powerful vasoconstrictor

36
Q

what triggers the RAAS system?

A

hypofiltration

37
Q

what happens when electrolyte concentrations fall?

A

aldosterone levels increase

38
Q

where is aldosterone released from?

A

secreted by golmerulosa cells of the adrenal cortex

39
Q

what is reabsorbed in the proximal tubule?

A

water
NaCl
amino acids
glucose
potassium
bicarb

40
Q

what moves into the proximal tubule?

A

H+
ammonium

41
Q

which part of the nephron is rich in aquaproins?

A

descending loop
water reabsorbed

42
Q

what is reabsorbed in the distal tubule?

A

NaCl, water and bicarb

43
Q

what is absorbed into the tubule in the distal tubule?

A

H+
ammonium
potassium

44
Q

what is the structure of transitional epithelium?

A

lower cells - cuboidal/ columnar
apical cells - cuboidal when not stretched

Genitourinary System (4 decks)

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