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Systems Physiology > Renal Physiology and Urine Production > Flashcards

Renal Physiology and Urine Production Flashcards

1
Q

What is the purpose of urine production?

A

To get rid of urea and creatinine

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2
Q

What is found in urine?

A

Normal metabolic waste products

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3
Q

What waste products are made in the liver?

A

Urea, creatinine, bilirubin

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4
Q

Where is urea reabsorbed?

A

Small amount in medullary collecting duct and 30-40% in PCT

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5
Q

Where is urea concentration the highest?

A

Collecting duct

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6
Q

What is creatinine made from?

A

Muscle breakdown

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7
Q

How much creatinine is reabsorbed in kidneys?

A

None

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8
Q

What is bilirubin made from?

A

Breakdown of RBC

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9
Q

What osmolarities are considered hypotonic?

A

Less than 300

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10
Q

What osmolarity is considered isotonic?

A

300

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11
Q

What osmolarities are considered hypertonic?

A

More than 300

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12
Q

What are the five steps of urine production?

A
  1. filtration
  2. reabsorption
  3. counter-current concentration
  4. secretion
  5. excretion
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13
Q

Where does filtration occur?

A

Glomerulus

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14
Q

What is the osmolarity at the glomerulus?

A

300

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15
Q

What is the equation for net glomerular filtration pressure?

A

Glomerular hydrostatic pressure - Bowman’s capsule hydrostatic pressure - glomerular osmotic pressure

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16
Q

What percentage of blood is in the kidneys at any time?

A

20%

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17
Q

What is glomerular filtration based on?

A

Size

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18
Q

What is the glomerulus composed of?

A

Fenestrated capillaries

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19
Q

What is the glomerulus reinforced by?

A

Basement membrane and podocytes

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20
Q

What is the normal glomerular filtration rate?

A

125 ml/min

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21
Q

What is different about filtrate compared to plasma?

A

No protein in filtrate

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22
Q

What is the equation for filtered load?

A

Plasma concentration x GFR

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23
Q

What does filtered load resemble?

A

How much of something can enter filtrate in a minute

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24
Q

What is the second step of urine production?

A

Tubular reabsorption

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25
Q

Where does tubular reabsorption occur?

A

Proximal convoluted tubule

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26
Q

What type of cells are found in the proximal convoluted tubule?

A

Columnar epithelial with microvilli

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27
Q

What percentage of all water and ions are reabsorbed in the PCT?

A

65%

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28
Q

Can percentage of water and ions reabsorbed in the PCT be altered?

A

No

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29
Q

Name five things reabsorbed in the PCT

A
  1. sodium
  2. chloride
  3. potassium
  4. bicarbonate
  5. all small molecules
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30
Q

What percentage of glucose and amino acids are reabsorbed in the PCT?

A

100%

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31
Q

What percentage of urea is reabsorbed in the PCT?

A

30-40%

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32
Q

Is urea reabsorption active or passive transport?

A

Passive

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33
Q

What is the transport system for glucose?

A

Secondary active sodium co-transport

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34
Q

What is the transport system for amino acids?

A

Secondary active sodium co-transport

35
Q

What is the transport system for water and small ions?

A

Osmosis

36
Q

What is the transport system for sodium at the luminal surface?

A

Diffusion

37
Q

What is the transport system for sodium at the anti-luminal surface?

A

Primary active transport

38
Q

What can reach a transport maximum?

A

Glucose, amino acids, sulfate, phosphate

39
Q

What does it mean when transport threshold is reached?

A

Some nephrons can no longer reabsorb and some molecules end up in the urine

40
Q

What does it mean when transport maximum is reached?

A

All nephrons can no longer reabsorb

41
Q

What is the third step of urine production?

A

Counter-current concentration

42
Q

Where does counter-current concentration occur?

A

Loop of Henle/ early DCT

43
Q

What is the descending loop of Henle permeable to?

A

Water only

44
Q

What is the ascending loop of Henle permeable to?

A

Salt only

45
Q

What is the transport system for NaCl at the thin ascending loop of Henle?

A

Passive transport

46
Q

What is the transport system for NaCl at the thick ascending loop of Henle?

A

Active transport

47
Q

What else is reabsorbed at the thick ascending loop of Henle besides NaCl?

A

Calcium and magnesium

48
Q

What is the osmolarity at the bottom of the loop of Henle?

A

1200

49
Q

What is the osmolarity at the thick ascending loop of Henle?

A

100

50
Q

What is the fourth step of urine production?

A

Tubular secretion

51
Q

Where does tubular secretion occur?

A

Late distal convoluted tubule and cortical region of the collecting duct

52
Q

What is the osmolarity at the late distal convoluted tubule and cortical region of the collecting duct?

A

300

53
Q

What five things are secreted from the peritubular capillary into the filtrate at tubular secretion?

A
  1. hydrogen ions
  2. ammonium ions
  3. phosphate ions
  4. drugs
  5. toxins
54
Q

By the end of the DCT, 99% of what is reabsorbed?

A

All water and dissolved solutes

55
Q

What is the reabsorption of water and dissolved solutes determined by?

A

Combined action of aldosterone and ADH

56
Q

Where does aldosterone mainly act?

A

Principal cells

57
Q

Where does aldosterone bind?

A

The nucleus

58
Q

What does aldosterone do at the nuclei of principal cells?

A

Increases the transcription of the sodium/potassium ATPase pumps

59
Q

What effect does increased transcription of NaK ATPase pumps have on absorption and secretion?

A

Increases sodium reabsorption and potassium secretion

60
Q

What does an increased sodium reabsorption and potassium secretion lead to?

A

Increased sodium concentration and decreased potassium in blood (opposite in urine)

61
Q

What is the “other” role of aldosterone?

A

Increases bicarbonate buffer system

62
Q

What is the effect of an increased bicarbonate buffer system?

A

Increased hydrogen ion secretion and bicarbonate reabsorption

63
Q

What does increased hydrogen ion secretion and bicarbonate reabsorption lead to?

A

Decreased pH of the urine, increased pH of the blood

64
Q

Where does ADH act?

A

Principal cells

65
Q

Where is ADH made?

A

Supraoptic nuclei of hypothalamus

66
Q

What is ADH made in response to?

A

Increased sodium concentration in the blood

67
Q

Where is ADH released from?

A

Posterior pituitary

68
Q

Where does ADH bind?

A

Anti-luminal surface of the cell

69
Q

What does ADH do?

A

Increases the transcription of aquaporins which are then inserted into the membrane

70
Q

How does ADH increase transcription of aquaporins?

A

Intracellular signalling

71
Q

What do aquaporins allow for?

A

Reabsorption of water into the DCT and collecting duct

72
Q

What does reabsorption of water in the DCT and collecting duct lead to?

A

Decreased concentration of sodium in the blood

73
Q

What is the fifth and final step of urine production?

A

Excretion

74
Q

Where does excretion occur?

A

Collecting duct

75
Q

What is the collecting duct permeable to?

A

Water with ADH only

76
Q

With ADH, the collecting duct holds the most ___ filtrate.

A

concentrated

77
Q

Without ADH, the collecting ducts holds the most ___ filtrate.

A

diluted

78
Q

What is the distal medullary portion of the collecting duct permeable to in addition to water with ADH?

A

Urea

79
Q

What is the osmolarity at the end of the collecting duct?

A

1200

80
Q

At what point does filtrate become urine?

A

Once in the renal pelvis

81
Q

What is the equation for excretion?

A

Filtration - reabsorption (filtered load) - transport maximum

82
Q

What is there no reabsorption of?

A

Creatinine

83
Q

What is the only site of active urea reabsorption?

A

Medullary collecting duct

Systems Physiology (11 decks)

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