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PL2022: Introductory Physiology II > Kidneys > Flashcards

Kidneys Flashcards

1
Q

What are the SIX functions of the kidneys?

A
  1. Regulation of extracellular fluid, volume and blood pressure
  2. Regulation of ECF osmolarity (280mOsm)
  3. Maintenance of ion balance
  4. Regulation of pH (7.4)
  5. Excretion of wastes (creatine and urea)
  6. Production of hormones (erythropoietin)
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2
Q

How many renal pyramids are in the kidney medulla?

A

8-15

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3
Q

What is the functional unit of the kidneys?

A

The nephron

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4
Q

How many nephrons are in each kidney and what are their functions?

A
  • 1 million nephrons per kidney
  • Deliver urine into the renal pelvis and into the bladder
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5
Q

What are the TWO principle types of nephrons?

A
  1. Cortical nephron (outer section of cortex)
  2. Juxtamedullary nephron (inner section of cortex)
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6
Q

Which nephron plays a central role in concentrated urine production?

A

Juxtamedullary nephron

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7
Q

What is the percentage of cardiac output that the renal artery receives?

A

20-25%

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8
Q

What does the Glomerular Capsule consist of?

A

A capillary bed (glomerulus) surrounded by a Bowman’s capsule

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9
Q

From what arteriole does the capillary bed receive blood?

A

From the AFFERENT arteriole and drains into the EFFERENT arterioles

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10
Q

What are the THREE barriers plasma passes through during glomerular filtration?

A
  1. Capillary fenestrations
  2. Glomerular basement membrane
  3. Inner layer of Bowman’s capsule
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11
Q

What are Pedicels?

A

Cytoplasmic extensions

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12
Q

What is Proteinuria?

A

Damage to slit diaphragms resulting in leakage of plasma protein into urine

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13
Q

What is filtration driven by and opposed by?

A

Driven by capillary hydrostatic pressure and opposed by plasma oncotic pressure (Starling forces) and Bowman’s capsule pressure

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14
Q

What is Glomerular Filtration Rate (GFR)?

A

Volume of filtrate produced by both kidneys per minute
(115ml for females and 125ml for males)

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15
Q

How much filtrate is produced every day?

A

180 litres a day

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16
Q

What is Renal Clearance?

A

The glomerular filtration rate

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17
Q

What proteins are used in nephrology clinically and in research?

A

Clinically - Creatine

Research - Insulin

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18
Q

How do vasoconstriction and vasodilation of afferent arterioles affect GFR?

A
  • Vasoconstriction REDUCES GFR
  • Vasodilation INCREASES GFR
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19
Q

What is the constant range that GFR is maintained to?

A

70-180mmHg

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20
Q

What is the Myogenic Response?

A
  • INCREASE in blood pressure leads to reflex CONSTRICTION of afferent arterioles
  • DECREASE in blood pressure leads to reflex DILATION of afferent arterioles
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21
Q

What are the specialised cells of the Juxtaglomerular Apparatus?

A

Macula densa

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22
Q

What is the function of the Macula Densa cells?

A

Detect elevated tubular NaCl concentrations and release ATP to trigger constriction of afferent arterioles, which reduces GFR

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23
Q

What is Tubularglomerular Feedback?

A

Homeostasis of GFR within each nephron

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24
Q

How much urine is produced daily?

A

1-2 litres

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25
Q

What is the percentage of filtrate reabsorbed and returned to the vasculature?

A

99%

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26
Q

What part of the nephron reabsorbs the filtrate?

A

The epithelial cells lining the inner wall of nephrons

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27
Q

How is Na+ reabsorbed in the Proximal Tubule?

A

Active transport

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28
Q

How do Cl- and water follow Na+ from filtrate in lumen into cells?

A

Passive transport
(electrostatic and osmotic gradient)

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29
Q

What are the specific transporters expressed in the Apical Membrane?

A
  • Na+/H+ exchanger
  • Na+/PO4- co-transporter
  • Na+/glucose co-transporter
  • Na+/Amino Acid co-transporter
  • Aquaporin 1 (water channel)
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30
Q

What is the osmolarity of plasma and glomerular filtrate?

A

300mOsm
(isosmotic)

31
Q

What is the percentage of salt and water reabsorbed in the PROXIMAL TUBULE?

A

65%

32
Q

What is the percentage of salt and water reabsorbed by the LOOP OF HENLE?

A

20%

33
Q

Where does urine concentration occur?

A

Collecting duct

34
Q

What is the Countercurrent Multiplier System?

A

Determines the osmolarity of urine

35
Q

How is Countercurrent Multiplier System related to interstitial fluid and tubular fluid?

A

CMS keeps osmolarity of interstitial fluid in medulla high and tubular fluid low

36
Q

Are the reabsorption of NaCl and water coupled?

A

No

37
Q

Are there aquaporins in the ASCENDING loop of Henle?

A

No
Just co-transporters for NaCl

38
Q

What happens in the ascending limb of the loop of Henle?

A

Tubular filtrate becomes hypotonic (more diluted) and interstitial fluid becomes hypertonic (less diluted)

39
Q

What is the DESCENDING loop of Henle permeable to?

A
  • Water but not salts
  • Cells here express AQP-1
40
Q

What happens in the DESCENDING loop of Henle?

A

Due to high osmolarity in interstitial fluid, water enters it and tubular fluid becomes more concentrated

41
Q

What is the osmolarity of the tubular fluid at the TOP of the loop?

A

1200-1400 mOsm

42
Q

What are Vasa Recta?

A

Long blood vessels that are parallel to the loop of Henle

43
Q

Is the medullary interstitial fluid more hypertonic or more hypotonic as it gets closer to the centre of the kidney?

A

Hypertonic

44
Q

What is the percentage of glomerular filtrate reabsorbed in the early nephron?

A

85%

45
Q

What is the percentage of glomerular filtrate that enters the distal nephron?

A

15%

46
Q

What happens to tubular fluid in the distal tubule?

A

It becomes more hypotonic
(100mOsm)

47
Q

What happens in the collecting duct?

A
  • Further salt and water is reabsorbed
  • Fluid leaving the collecting duct is urine
48
Q

How is the permeability of the collecting duct activated?

A

By the release of ADH which moves AQP-2 to apical membrane

49
Q

What is the blood plasma osmolarity during dehydration?

A

Over 300mOsm

50
Q

What does dehydration activate?

A

Osmoreceptors in the hypothalamus which releases ADH/Vasopressin

51
Q

What does ADH bind to?

A

Vasopressin receptors

52
Q

Are there any water transporters in the loop of Henle?

A

No

53
Q

What is the normal concentratoin of Na+ in plasma?

A

135-145mOsm

54
Q

What is the percentage of filtered Na+ reabsorbed?

A

90%

55
Q

What hormone regulates the reabsorption of the remaining 10% of Na+ in the collecting duct?

A

Aldosterone

56
Q

How is Aldosterone released?

A

Released by low blood pressure or low Na+ plasma concentration by adrenal glands

57
Q

What is RAAS and what does it do?

A

Renin-Angiotensin-Aldosterone-System
Reduces blood volume/pressure and low Na+ intake

58
Q

What do reduction of blood pressure/volume and low Na+ intake cause?

A
  1. Reduction in renal afferent arteriolar pressure
  2. Reduced Na+ concentration in tubular filtrate
  3. Renal sympathetic nerves are activated by baroreceptors
59
Q

What do the causes of the reduction of blood pressure/volume and low Na+ stimulate?

A

Granular cells in the juxtaglomerular apparatus to release renin into circulation

60
Q

What does Renin do?

A

Converts plasma protein angiotensinogen to a smaller protein; angiotensin-1

61
Q

What is Angiotensin-1 converted to in the lung capillaries?

A

Angiotensin-2

62
Q

What is Natriuresis?

A

Increased excretion of Na+ into urine

63
Q

What are the functions of Atrial Natriuretic Peptide?

A
  • Increase GFR
  • Inhibit Na+ and water reabsorption in collecting duct
  • Inhibition of renin excretion
64
Q

What hormone helps to maintain K+ concentration and what is the normal range?

A

Aldosterone maintains K+ concentration at 3.5-5 meq/L

65
Q

What do hyperkalemia and hypokalemia cause?

A

Hyperkalemia - Cardiac arrhythmias

Hypokalemia - Muscle weakness

66
Q

What is the percentage of HCO3 reabsorbed by the proximal tubule?

A

80%

67
Q

What is acidosis and alkalosis?

A

Acidosis - Drop in pH

Alkalosis - Increase in pH

68
Q

What cells correct acidosis and alkalosis?

A

Proximal tubule cells

69
Q

Where are glucose and amino acids filtered?

A

At glomerulus

70
Q

How does glucose and amino acid reabsorption occur?

A

Via proximal tubule via Na+/glucose co-transporter and Na+/amino acid co-transporter

71
Q

What is the normal concentration of glucose in plasma?

A

100-150 mg/100ml

72
Q

What is Glucosuria?

A

Glucose in urine

73
Q

What is the transport maximum of glucose transporters?

A

200 mg/100ml

PL2022: Introductory Physiology II (6 decks)

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