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SUGER > Renal physiology > Flashcards

Renal physiology Flashcards

1
Q

what is the function of the kidneys?

A
  • endocrine function
  • maintain H2O, NaCland pH balances
  • excrete waste
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2
Q

how much blood does the kidney receive per minute?

A

1L - 20% of the cardiac ouput

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3
Q

what determines whether something can cross the filtration barrier?

A
  • pressure exerted on blood
  • size of molecule
  • charge or molecule
  • rate of blood flow
  • whether or not a substance is bound to a plasma protein or not
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4
Q

what makes up the filtration barrier?

A
  • capillary endothelial cells (fenstrated in kidney)
  • basement membrane
  • slit diaphragm between podocyte foot processes
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5
Q

define GFR.

A

Glomerular filtrate rate - the filtration volume per unit time

GFR = K(Pgc-Pbs) - (osmotic pressureGC - osmotic pressureBS)

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6
Q

describe autoregulation of GFR.

A
  • pressure within afferent arteriole rise
  • stretches the vessel wall
  • triggers contraction of smooth muscle
  • arteriole vasoconstriction

happens to prevent an increase in systemic pressure reaching glomerular capillaries

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7
Q

what are the components for the juxtagolmerular apparatus?

A
  • macula densa cells in the DCT which lie close to the bowmans capsule of the same nephron
  • juxtaglomerular granular cells
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8
Q

what is the purpose of the juxtaglomerular apparatus?

A

to control GFR of an individual nephron by tubuloglomerular feedback

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9
Q

how does thejuxtaglomerular apparatus work?

A
  • Macula densa cells detect the arrival of NaCl
  • they release prostaglandins in response
  • prostaglandins cause granular cells to release renin activating RAAS
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10
Q

how do we measure GFR?

A

calculated by measuring a substance that is

  • freely filtered (same conc in blood and tubular fluid)
  • not secreted or absorbed in the tubules
  • not metabolised

GFR = (conc of m in urine x urine flow rate)/conc of m in plasma

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11
Q

clinically what substance do we measure in blood and urine for GFR?

A

creatinine

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12
Q

what is the filtration fraction? how is it worked out?

A

the ratio of blood passing through the glomerulus and plasma filtered

Filtration fraction = GFR/renal plasma flow

usually = aprrox 0.2

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13
Q

define osmolality and osmolarity.

A 
osmolality = measure of the number of particles dissolved per Kg of fluid  
osmolarity = measure of the number of dissolved particles per L of fluid
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14
Q

what takes place in the PCT of the nephron?

A

bulk reabsorption of

  • NaCl
  • glucose
  • amino acids
  • HCO3-
  • PO4-

secretion of organic ions

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15
Q

how is glucose and phosphate reabosrbed?

A

with Na+ via a symporter

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16
Q

How is bicarbonate reabsorbed?

A
  • H+ is transported into the lumen via an antiporter with sodium
  • H+ reacts with HCO3- giving H2O and CO2
  • CO2 diffuses into the cell and carbonic anhydrase converts it back into bicarbonate
  • HCO3- is transported into the capillary with Na+ via a symporter
17
Q

what drives bulk absorption?

A

Na+/K+ ATPase removing Na+ to maintain a concentration gradient

18
Q

what parts of the loop of henle are permeable to water? what parts aren’t?

A
  • thin descending limb is permeable

- thin and thick ascending limbs are impermeable

19
Q

how is the countercurrent multiplication factor generated?

A
  • solutes (Na+, Cl- and K+) are actively pumped out of the lumen into the interstitium lowering luminal osmolality and increasing medullary osmolality
  • this draws out H2O out of the descending limb increasing luminal osmolality
  • continuous flow causes fluid from descending to move to ascending limb

the process repeats generating a hypertonic medullary interstitum

20
Q

what takes place in the DCT of a nephron?

A

continues diluting the urine by reabsorption of Na+ in an impermeable setting

21
Q

what are the 2 cell types in the collecting duct?

A
  • principal cells

- intercalated cells

22
Q

what takes place in the collecting duct?

A
  • hormone regulation of Na+ reabsorption
  • hormone regulated water reabsorption
  • acid secretion
23
Q

where does aldosterone act? what does it do?

A
  • acts on principal cells in the collecting duct
  • it binds to nuclear receptors
  • increases the transcription of ENaC channels and NaKATPase produced and inserted into the luminal membrane
  • this increases Na+ reabsorption and K+ excretion do to the change of charge inside the sell when Na+ influxes
24
Q

Where does ADH act? what does it do?

A
  • acts on the principal cells in the collecting duct
  • Binds to adenyl-cyclase coupled vasopressin receptor
  • this activates cAMP which causes a cascade of enzyme controlled reactions causes the insertion of vesicles containing aquaporin 2 chennels in the apical membrane

this increases water permeability in the collecting duct

25
Q

what happens in the intercalated cells of the collecting duct?

A
  • Acid secretion
  • H+ is secreted by an ATPase and a K+ antiporter
  • the action of carbonic anhydrase generates the H+ molecules for excretion
26
Q

what affect does atrial natriuretic peptide have?

A
  • renal vasodilator
  • inhibits aldosterone release
  • closes ENaC channels in collecting duct

reduces blood volume and therefore blood pressure

27
Q

what affect does angiotensin 2 have?

A
  • causes the release of aldosterone
  • vasocontricts (esp. efferent arteriole)
  • Na reabsorption of the proximal tubule
  • causes the release of ADH
  • causes thirst

SUGER (8 decks)

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