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Physiology > 11-13 - The Renal System > Flashcards

11-13 - The Renal System Flashcards

1
Q

The majority of blood flow to the kidneys goes to the…

A

Renal cortex

(93%)

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2
Q

Which type of nephron is responsible for the production of concentrated urine?

A

Juxtamedullary nephrons

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3
Q

Name the 6 main parts of the nephron…

A
  • Bowman’s capsule
  • Proximal tubule
  • Loop of Henle
  • Distal tubule
  • Collecting tubules
  • Collecting duct
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4
Q

The vasa recta surround the…

A

Nephron

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5
Q

Describe the vasculation of the nephrons…

A
  1. Afferent arterioles
  2. Capillaries (at glomeruli)
  3. efferent arterioles
  4. peritubular capillaries (vasa recta)
  5. renal veins
  6. inferior vena cava
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6
Q

Outline the 3 functions of the kidneys…

A
  1. Homeostatic regulation of water/ion content of blood
  2. Excretion of metabolic waste (urea, creatinine, urobilinogen etc)
  3. Production of hormones
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7
Q

Name 4 hormones produced or activated in the kidneys…

A
  • erythropoietin
  • renin
  • prostaglandins and kinins
  • vitamin D (activated)
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8
Q

Which 3 processes occur at the nephron?

A
  • Glomerular filtration
  • Tubular reabsorption
  • Tubular secretion
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9
Q

All plasma constituents are filtered through the glomerulus, except…

A

Larger proteins

(>67kDa)

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10
Q

GFR stands for…

A

Glomerular filtration rate

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11
Q

The average GFR is…

A

180L/day

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12
Q

__% of cardiac output is recieved by the kidneys and __% of plasma filters into the nephron (this is known as the _______ ___________)

A

25% of cardiac output is recieved by the kidneys and 20% of plasma filters into the nephron (this is known as the filtration fraction)

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13
Q

Podocytes are cells in the Bowman’s capsule in the kidneys that wrap around the capillaries of the…

A

Glomerulus

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14
Q

The renal corpuscle is the bundle of ___________ ___________ within _____________ ___________

A

The renal corpuscle is the bundle of glomerular capillaries within Bowman’s capsule

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15
Q

Glomerular capillaries are ___________, allowing blood to be filtered out

A

Glomerular capillaries are fenestrated, allowing blood to be filtered out

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16
Q

The basement membrane between the fenestrated capillary and the podocyte feet forms the main…

A

Filtration barrier

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17
Q

99% of filtrate is…

a) Excreted
b) Reabsorbed
c) Secreted
d) Filtered

A

99% of filtrate is…

a) Excreted

b) Reabsorbed

c) Secreted
d) Filtered

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18
Q

1% of filtrate is…

a) Excreted
b) Reabsorbed
c) Secreted
d) Filtered

A

1% of filtrate is…

a) Excreted

b) Reabsorbed
c) Secreted
d) Filtered

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19
Q

A small amount of secretion contributes to the excreted urine, which mainly occurs at the…

A

Proximal convoluted tubule

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20
Q

Reabsorption involves the movement of solutes out of the __________ and back into capillaries via _________ ___________ mechanisms.

A

Reabsorption involves the movement of solutes out of the filtrate and back into capillaries via epitheleal transport mechanisms.

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21
Q

What is the difference between epithelial transcellular transport and paracellular transport…

A

Epipethelial transcellular transport = through cells/ across cell membranes

Paracellular transport = via cell-cell junctions (doesn’t cross cell membranes)

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22
Q

Summarise the cellular mechanisms by which solutes move from the filtrate across the epithelial cells to the peritubular capillary…

A
  • Co-transporters
  • Transporters
  • Membrane pumps
  • Membrane carriers
  • Membrane channels
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23
Q

Summarise the passive mechanisms by which solutes move from the filtrate across the epithelial cells to enter the peritubular capillaries…

A
  • Leak channels
  • Diffusion (if membrane permeable solute)
  • Paracellular transport (via cell-cell junctions)
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24
Q

The route taken by solutes to cross the epithelial cells depends on ____________ gradient and the ___________ of epitheleal junctions.

A

The route taken by solutes to cross the epithelial cells depends on electrochemical gradient and the permeability of epitheleal junctions.

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25
Q

The structure of the proximal convoluted tubule (PCT) is adapted for 2 functions…

A
  1. Reabsorption
  2. Secretion
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26
Q

Describe the notable structural features of the PCT…

A
  • The apical membrane has microvilli (maximise SA for reabsorption)
  • Presence of ER, golgi, lysosomes and vacuoles (synthesis of membrane proteins)
  • The basolateral membrane has interdigitations (reduce distance to mitochondria to provide energy for active transport)
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27
Q

Reabsorption at the PCT

Name 5 types of substance reabsorbed at the PCT…

A
  1. Ions (Chiefly sodium, but also chloride, potassium and calcium)
  2. Water (Paracellular via osmosis)
  3. Glucose (via co-transport and carriers)
  4. Urate (also secreted)
  5. Low mW proteins and amino acids
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28
Q

In diabetes mellitus the appearence of glucose in the urine is due to the…

A

Saturation of transporters by excessive glucose (plasma concentration exceeds renal threshold)

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29
Q

Sodium is reabsorbed at the PCT…

a) actively
b) passively
c) both actively and passively
d) sodium is not reabsorbed at the PCT

A

Sodium is reabsorbed at the PCT…

a) actively
b) passively

c) both actively and passively

d) sodium is not reabsorbed at the PCT

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30
Q

Describe the ways in which sodium can be reabsorbed at the PCT (and if they are active/passive)…

A
  • Actively via sodium/potassium ATPase pump
  • Passively via
    • Leak channels
    • Ion exchange with H+
    • Cotransport with essential solutes (glucose and amino acids)
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31
Q

The reabsorption of other ions (Cl-, K+, Ca2+) at the PCT can occur both…

A

Paracellularly or transcellularly (by diffusion)

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32
Q

Urate is reabsorbed into the PCT via…

A
  • Organic anion transporters
  • Paracellularly
  • Transcellularly
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33
Q

Urate is secreted via…

A

Organic anion transporters

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34
Q

Secretion at the PCT is a(n) (passive / active) process which transfers molecules from the __________ __________ back into the tubule.

A

Secretion at the PCT is an active process which transfers molecules from the peritubular capillary back into the tubule.

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35
Q

List anionic endogenous compounds secreted from peritubular capillaries to tubules…

A
  • Urate
  • cAMP
  • Bile salts
  • Prostaglandins
36
Q

List examples of anionic drugs secreted from peritubular capillaries to tubules…

A
  • Penicillin
  • Aspirin
  • Diuretics
37
Q

List cationic endogenous compounds secreted from peritubular capillaries to tubules…

A
  • Noradrenaline
  • Adrenaline
  • Dopamine
  • Creatinine
38
Q

List examples of cationic drugs secreted from peritubular capillaries to tubules…

A
  • Atropine
  • Morphine
  • Quinine
  • Amiloride
39
Q

The composition of tubular fluid leaving the PCT…

List the reabsorption rates for:

  • Sodium ions, potassium ions and water
  • Urea and urate
  • Hydrogen carbonate ions
  • Glucose and amino acids
A
  • Sodium ions, potassium ions and water - 66%
  • Urea and urate - 50%
  • Hydrogen carbonate ions - 80%
  • Glucose and amino acids - 100 %
40
Q

The tubular fluid leaving the PCT is…

a) Isoosmotic with plasma (300mOsm)
b) Hyperosmotic with plasma (>300mOsm)
c) Hypoosmotic with plasma (<300mOsm)

A

The tubular fluid leaving the PCT is…

a) Isoosmotic with plasma (300mOsm)

b) Hyperosmotic with plasma (>300mOsm)
c) Hypoosmotic with plasma (<300mOsm)

41
Q

The descending limb of the loop of Henle is:

a) permeable to water and solutes
b) permeable to water not solutes
c) permeable to solutes not water
d) impermiable to water and solutes

A

The descending limb of the loop of Henle is:

a) permeable to water and solutes

b) permeable to water not solutes

c) permeable to solutes not water
d) impermiable to water and solutes

42
Q

The ascending limb of the loop of Henle is:

a) permeable to water and solutes
b) permeable to water not solutes
c) permeable to solutes not water
d) impermiable to water and solutes

A

The ascending limb of the loop of Henle is:

a) permeable to water and solutes
b) permeable to water not solutes

c) permeable to solutes not water

d) impermiable to water and solutes

43
Q

The collecting duct is:

a) permeable to water and relatively impermiable to urea
b) permeable to water and urea
c) permeable to urea and relatively impermiable to water
d) permeable to water not to solutes

A

The collecting duct is:

a) permeable to water and relatively impermiable to urea
b) permeable to water and urea

c) permeable to urea and relatively impermiable to water

d) permeable to water not to solutes

44
Q

The osmolarity of the tubular fluid at the bottom of loop of Henle is…

a) 300
b) 1200
c) 100
d) 75

(mOsM)

A

The osmolarity of the tubular fluid at the bottom of loop of Henle is…

a) 300

b) 1200 (hypertonic to the plasma)

c) 100
d) 75

(mOsM)

45
Q

The osmolarity of the tubular fluid at the distal tubule (after loop of Henle) is:

a) 300
b) 1200
c) 100
d) 75

(mOsM)

A

The osmolarity of the tubular fluid at the distal tubule (after loop of Henle) is:

a) 300
b) 1200

c) 100 (hypotonic to the plasma)

d) 75

(mOsM)

46
Q

( Increased / decreased ) water reabsorption leads to the formation of concentrated urine.

A

Increased water reabsorption leads to the formation of concentrated urine.

47
Q

Which hormone enables the production of concentrated urine (and by what mechanism)?

A

Anti-diuretic hormone (ADH/ vasopressin) increases the permeability of the collecting duct to H2O.

More H2O is then reabsorbed, increasing the OsM

48
Q

What maintains the osmotic gradient in the medullary interstitium?

A

Counter-current systems

49
Q

Describe the 3 properties of countercurrent systems…

A
  1. 2 flows in opposing directions
  2. 2 vessels in close proximity
  3. passive transfer of molecules between vessels
50
Q

A countercurrent multiplier system is the use of _______________ to enhance countercurrent flow

A

A countercurrent multiplier system is the use of active transport (of solutes) to enhance countercurrent flow

51
Q

Name the two types of nephron found in the kidneys…

A
  • Cortical
  • Juxtamedullary
52
Q

(In the presence of ADH/vasopressin) water is reabsorbed from the collecting duct and removed from the medulla by the…

A

Ascending vasa recta

53
Q

In the absence of ADH/vasopressin, the wall of the collecting duct is…

A

Impermiable to water

54
Q

Concentrated urine has ( high / low ) osmolarity

A

Concentrated urine has high osmolarity

55
Q

Dilute urine has ( high / low ) osmolarity

A

Dilute urine has low osmolarity

(osmolarity is concentration expressed as the total number of solute particles per litre. Less concentrated urine has fewer solute particles per litres, so the osmolarity is lower)

56
Q

Plasma pH is tightly regulated between a normal range of…

A

pH 7.38 - 7.42

57
Q

Name 4 buffers present in the plasma which help to regulate pH…

A
  • Cellular proteins
  • Haemoglobin
  • HPO42- (hydrogen phosphate)
  • HCO3- (hydrogen carbonate)
58
Q

Other than buffers present in the plasma, which 2 other mecanisms contribute to the maintainence of plasma pH?

A
  • Respiratory adjustment (via CO2)
  • Renal adjustment (via H+, HCO3- secretion/absorption)
59
Q

In response to low pH (Acidosis), Type A intercalated cells in the collecting duct excrete:

a) H+ and absorb HCO3-
b) HCO3- and absob H+
c) HPO42- and absorb HCO3-
d) urea and absorb H2O

A

In response to low pH (Acidosis Type A), intercalated cells in the collecting duct excrete:

a) H+ and absorb HCO3

Thus increasing the pH of the plasma

60
Q

In response to high pH (Alkalosis), type B intercalated cells in the collecting duct excrete:

a) H+ and absorb HCO3-
b) HCO3- and absob H+
c) HPO42- and absorb HCO3-
d) urea and absorb H2O

A

In response to high pH (Alkalosis), type B intercalated cells in the collecting duct excrete:

b) HCO3- and absob H+

Thus increasing H+ in plasma and lowering the pH

61
Q

Diuretics are drugs that promote…

A

Urine excretion (formation of urine)

62
Q

ADH/vasopressin increases the permeability of the ____________ to _____ resulting in ____________ _______

A

ADH/vasopressin increases the permeability of the collecting duct to H2O resulting in concentrated urine

63
Q

Describe the cellular action of ADH in 3 steps…

A
  1. ADH binds to V2 receptors
  2. Adenyl cyclase generates cAMP and activates protein kinases
  3. More aquaporin 2 channels inserted into apical membrane (which increases water permeability)
64
Q

Name 3 inputs which control the release of ADH…

A
  1. Hypothalamic osmoreceptors
  2. Atrial stretch receptors
  3. Carotid and aortic baroreceptors
65
Q

Signals from the hypothalamic neurones trigger release of ADH/vasopressin from the

a) anterior pituitary
b) thalamic neuclei
c) posterior pituitary
d) vasa recta

A

Signals from the hypothalamic neurones trigger release of ADH/vasopressin from the

a) anterior pituitary
b) thalamic neuclei

c) posterior pituitary

d) vasa recta

66
Q

Name the two types of control over ADH/vasopressin secretion…

A
  • Plasma osmolarity (via hypothalamic osmoreceptors) - this is osmolar control
    • Set point 280mOsM
  • Blood volume/pressure (via atrial stretch receptors and carotid & aortic baroreceptors) - this is non-osmolar control
    • Responsible for MUCH LARGER output of ADH
    • 10% decrease in BV = activated!
67
Q

Alcohol ( stimulates / inhibits ) ADH release

A

Alcohol inhibits ADH release

68
Q

Name some normal and inappropriate stimuli that may lead to ADH release…

A
  • Physiological stimuli
    • High temp, exercise, pain, stress
  • Inappropriate stimuli
    • Tumours, opiates, nicotine MDMA
69
Q

Outline how MDMA can result in hyponatremia (low blood sodium)

A
  • MDMA stimulates ADH secretion, reducing fluid out
  • MDMA stimulates thirst reflex, increasing fluid in
70
Q

Diabetes insipidus is the result of…

A

ADH deficiency

71
Q

Diabetes insipidus can be either central or nephrogenic, differentiate between these two types…

A
  • Central - deficiency of ADH secretion
  • Nephrogenic - nephron is insensitive to secreted ADH
72
Q

Summary of sodium ion handling by the nephron

Most Na+ is reabsorbed by the _____________(67%).

No reabsorption occurs at the _______________.

Some reabsorption occurs at the ___________________ (25%).

A further 5% is reabsorbed at the distal convoluted tubule and finally 3% at the ______________.

0.4% of Na+ is excreted in ________ urine.

A

Summary of sodium ion handling by the nephron

Most Na+ is reabsorbed by the proximal convoluted tubule (67%).

No reabsorption occurs at the loop of Henle.

Some reabsorption occurs at the thick ascending limb (25%).

A further 5% is reabsorbed at the distal convoluted tubule and finally 3% at the collecting duct.

0.4% of Na+ is excreted in dilute urine.

73
Q

The Renin-Angiotensin-Aldosterone axis is responsible for maintaining ____________ by increasing reabsorption of __________

A

The Renin-Angiotensin-Aldosterone axis is responsible for maintaining blood volume by increasing reabsorption of sodium ions

74
Q

Renin is released by juxtaglomerular (JG) cells in response to 3 stimuli…

A
  • Decreased blood pressure (afferent arteriole stretch receptors)
  • Decreased central blood pressure (renal sympathetic nerve stimulation)
  • Decreased sodium chloride (in macula densa* cells)

*Macula densa cells line the wall of the distal tubule in the area where it meets the collecting duct.

75
Q

Renin released by the JG cells goes on to catalyse the conversion of…

A

Angiotensiongen

to

Angiotensin I

(in the plasma)

76
Q

Angiotensis I is converted to Angiotensin II by…

A

Angiotensin-converting enzyme (ACE)

(in the plasma)

77
Q

Angiotensin II is converted to…

A

Aldosterone

(in the adrenal cortex)

78
Q

Aldosterone increases the reabsorption of sodium ions in the kidneys, which subsequently increases the volume of…

A

the ECF

79
Q

On a cellular level how does aldosterone promote the reabsorption of Na+?

A
  • Aldosterone binds to a cytoplasmic receptor
  • This increases:
    • ENaC channels on apical surface
    • Na+/K+ pumps on basolateral surface
80
Q

How does the increased reabsorption of Na+ triggered by aldosterone result in increased blood volume?

A

Increased Na+ reabsorption (Cl- follows) -> water follows

81
Q

Angiotensin II has a variety of effects, including…

A
  • Stimulation of aldosteron release
  • thirst sensation
  • vasoconstriction
  • increases noradrenaline release
  • inhibits baroreceptor reflex
82
Q

The formation of renal caculi (kidney stones) is known as ______________ and is due to the supersaturation of filtrate.

A

The formation of renal caculi (kidney stones) is known as nephrolithiasis and is due to the supersaturation of filtrate.

(nephro - kidney, lithiasis - formation of calculi. Gall bladder stones are cholelithiasis)

83
Q

Micturition (peeing)

The internal sphincter is (smooth muscle / skeletal muscle) contracted passively.

The external sphincter is (smooth muslce / skeletal muscle) contracted by tonic stimulation.

A

Micturition (peeing)

The internal sphincter is smooth** **muscle contracted passively.

The external sphincter is skeletal** **muscle contracted by tonic stimulation.

84
Q

ANP stands for…

A

Atrial Naturetic Peptide

85
Q

The release of ANP is triggered by the increase in atrial stretch resulting from increased blood volume.

Name 3 impacts of ANP…

A
  • Hypothalamus decreases ADH release
  • Kidneys decrease renin release, increased GFR and decreased NaCl/H2O reabsorption
  • Adrenal cortex inhibits aldosterone release

Physiology (17 decks)

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