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Renal and Urology > Physiological Functions of the Kidneys > Flashcards

Physiological Functions of the Kidneys Flashcards

1
Q

roles of the kidneys

A

regulating fluid volume
regulating conc. of electrolytes
regulation of acid-base balance
excreting waste
conserving nutrients
hormone secretion

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2
Q

which hormones and enzymes are secreted by the kidneys

A

erythropoetin - hormone
calcitriol - hormone
renin - enxyme

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3
Q

when is erythropoeitin released and what is its function

A

in response to hypoxia in the renal circulation
it stimulates erythropoiesis (RBC production) in the bone marrow

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4
Q

what is the role of calcitriol

A

it is the activated form of vitamin D and it promotes intestinal absorption of calciu,

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5
Q

what is the role of calcitriol

A

it is the activated form of vitamin D and it promotes intestinal absorption of calcium

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6
Q

what is the role of renin and where and when is it released?

A

released from juxtaglomerular apparatus
released in response to reduction in tubular flow or sodium content
regulates angiotensin and aldosterone levels which control blood pressure

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7
Q

what functions of the kidney play a crucial role in blood pressure control?

A

renin release
regulation of fluid volume and plasma electrolytes

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8
Q

what muscle needs to relax to allow urine to drain through the urethra and is it voluntary or involuntary

A

sphincter muscle
voluntary

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9
Q

what two layers surround the kidneys

A

renal fascia - tough connective tissue
capsule of peri-renal fat

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10
Q

what structures are found in the renal hilum

A

first part the ureter
nerves
arteries and veins

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11
Q

what is the basic functional unit of the kidney

A

nephron

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12
Q

how many nephrons are in a kidney

A

~1 million

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13
Q

what is urea

A

the nitrogen containing end product of protein metabolism

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14
Q

what part of the body has the most control over the hydration status of the body

A

the kidneys

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15
Q

what is the glomerulus and what is it enclosed within

A

a bundle of specialised capillaries with a permeable membrane
enclosed within Bowman’s capsule

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16
Q

which type of arteriole supplies the glomerulus and which type returns contents to the systemic circulation

A

afferent supplies
efferent drains

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17
Q

what percentage of sodium and chloride are reabsorbed in proximal convoluted tubule

A

65%

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18
Q

what is recovered in the PCT

A

sodium, potassium, calcium, magnesium
phosphate and chloride ions
bicarbonate
glucose
amino acid
urea
water

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19
Q

how are sodium, potassium and chloride reabsorbed in the PCT

A

by passive transport

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20
Q

how is glucose reabsorbed in the PCT

A

cotransported with sodium

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21
Q

how are calcium and magnesium reabsorbed in the PCT

A

they compete for exchange with sodium ions

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22
Q

how is phosphate reabsorbed in the PCT

A

reabsorbed with sodium

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23
Q

how is water reabsorbed in the PCT

A

osmotically with solutes through aquaporin channels
water follows movement of solutes

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24
Q

what is actively excreted in the PCT

A

creatinine, uric acid and many drugs

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25
Q

where does the loop of henle descend into and what is a key characteristic of this region

A

the renal medulla
it is highly concentrated

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26
Q

what is reabsorbed in the descending limb of LoH

A

water

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27
Q

how is water reabsorbed in the DL or LoH

A

by osmosis as the extratubular concentration is high

28
Q

how is the high concentration maintained in the renal medulla

A

by countercurrent exhange process where urea is recycled between the tubules and interstirium

29
Q

what is reabsorbed in the ascending limb of LoH

A

sodium, potassium and chloride ions
calcium and magnisum ions

30
Q

how is sodium, potassium and chloride reabsorbed in the LoH

A

by a specialised symporter protein which transports a sodium ion, two chloride ions and a potassium ion

31
Q

how is calciuma and phosphate reabsorbed in the ascending limbd og LoH

A

passive transport

32
Q

what percentage of sodium and chloride are reabsorbed in the DL of LoH

A

0%

33
Q

what percentage of sodium and chloride are reabsorbed in the AL of LoH

A

25%

34
Q

what percentage of sodium and chloride are reabsorbed in the DCT

A

10%

35
Q

what is reabsorbed in the DCT

A

sodium and chloride ions
calcium

36
Q

how are sodium and chloride ions reabsorbed in the DCT

A

in first part - by symporter protein
in second part - sodium reabsorbed in exchange for excretion of potassium or hydrogen

37
Q

what stimulates the reabsorption of sodium in exchange for excretion of potassium or hydrogen in the distal part of the DCT

A

aldosterone

38
Q

what is the function the reabsorption of sodium in exchange for excretion of potassium or hydrogen in the distal part of the DCT

A

regulation of pH of the urine and body

39
Q

what stimulates calcium reabsorption in the body

A

parathyroid hormone

40
Q

what is reabsorbed in the collecting duct

A

sodium
water

41
Q

what is osmolality

A

the relative proportions of salt and water in the body

42
Q

what structure detects significant rises in plasma osmolality

A

hypothalamus

43
Q

how does the body respond to a significant rise in plasma osmolality

A
  1. hypothalamus detects it
  2. communicates with posterior pituitary gland
  3. vasopressin/ADH released
  4. vasopressin causes aquaporins to translocate to the membrane of the collecting duct cells
  5. this allows water to cross the normally impermeable membrane and be reabsorbed in the body by the vasa recta
  6. this increases the plasma volume of the body
44
Q

what lies next to the afferent arteriole in each glomerulus and why

A

ascending limb of LoH
allows for specialised tubular cells called the macula densa to provide feedback regulartion in response to changes in the tubular content of water and electrolytes

45
Q

when is the renin angiotensin system activated

A

hypotension
hypovolaemia

46
Q

where is the macula densa found

A

between LoH and DCT

47
Q

what type of cells make up the macula densa

A

juxtaglomerular cells

48
Q

what are juxtaglomerular cells sensitive to

A

the concentration of sodium chloride in tubular fluid
the pressure in the afferent arteriole
signals from sympathetic nervous system

49
Q

an increase/decrease of sodium chloride concentration stimulates release of renin

A

deccrease

50
Q

what reaction does renin catalyse

A

angiotensinogen -> angiotensin I

51
Q

what enzyme catalyses angiotensin I -> angiotensin II

A

angiotensin converting enzyme

52
Q

what type of drug inhibits the formation of angiotensin II

A

ACEi (e.g. ramipril)

53
Q

how does angiotensin increase blood pressure

A

constricts efferent arteriole to increase glomerular capillary pressure and filtration
systemic vasconstriction
stimulates thirst
stimulate release of vasopressin which conserves water
stimulates release of aldosterone which conserves sodium

54
Q

what hormone is in charge of sodium conservation and where is it released from

A

aldosterone
adrenal cortex

55
Q

what hormone is in charge of water conservation and where is it released from

A

vasopressin
posterior pituitary

56
Q

what is the GFR a measure of

A

the performance of the kidneys
volume of plasma filtered at the kidneys every minute

57
Q

what is a typical GFR of a healthy adult

A

120mL/minute

58
Q

how much kidney function is lost with healthy ageing

A

can be up to 50% in 80 year old

59
Q

what are the consequences of reduced kidney function due to disease

A

reduced clearance of waste products, ions, drugs, water and acid
uraemia and reduced erythropoietin formation -> anaemia
phosphate retention and failure to convert precursors to vitamin D -> renal bone disease

60
Q

what are the three categories of acute renal impairment

A

pre-renal
renal
post renal

61
Q

why does pre-renal renal impairment occur

A

failure of sufficient blood flow getting to the kidneys

62
Q

common causes of pre renal renal impairment

A

systemic dehydration due to illness or diuretics
low arterial blood pressure due to drugs or haemorrhage
blockage of major renal arteries due to atherosclerosis or thrombosis
vasoconstriction of cortical vessels because of drugs (e.g. NSAIDs)

63
Q

what are renal causes of renal impairment

A

intrinsic renal disease or damage due to drugs or other toxins

64
Q

what are post renal causes of renal impairment

A

renal impairment due to obstruction of the urinary tract commonly due to
- compression of ureter between kidney and bladder as a result of tumour
- obstruction of bladder outflow (e.g. due to prostate disease)

65
Q

is damage caused by AKI reversible

A

yes, usually
but may result in permanent reduction in baseline GFR

Renal and Urology (16 decks)

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