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BRS Term 2 > The Genitourinary System (38) > Flashcards

The Genitourinary System (38) Flashcards

1
Q

What are the functions of the kidney?

A
  • excretion of useless metabolic products: urea, uric acid, creatinine
  • excretion of foreign substances: drugs
  • regulation of body fluids, electrolytes and acid-base balance
  • control of blood pressure
  • secretion of hormones: erythropoietin, renin
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2
Q

What is the structure of the kidney?

A 
cortex- outer layer
medulla- middle region
renal artery- blood in
renal vein- blood out
ureter- urine out
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3
Q

What is the passage of blood into and out of the kidney?

A

renal artery–> segmental artery–> interlobar artery–> arcuate artery–> interlobular artery–> afferent arteriole–> glomerular capillaries–> efferent arteriole–> peritubular capillaries–> interlobular vein–> arcuate vein–> interlobar vein–> renal vein

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4
Q

What is the function of the detrusor muscle in the bladder?

A

contracts to build pressure in the urinary bladder to support urination

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5
Q

What is the function of the trigone in the bladder?

A

stretching of this triangular region to its limit signals the brain about the need for urination

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6
Q

What is the function of the internal sphincter in the bladder?

A

involuntary control to prevent urination

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7
Q

What is the function of the external sphincter in the bladder?

A

voluntary control to prevent urination

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8
Q

What is the function of the bulbourethral gland?

A

produces thick lubricant which is added to watery semen to promote sperm survival

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9
Q

What is the structure of the nephron?

A
  • glomerulus
  • Bowman’s capsule
  • proximal convoluted tubule
  • loop of Henle
  • distal convoluted tubule
  • collecting duct
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10
Q

What is reabsorbed into the bloodstream at the proximal convoluted tubule?

A

Na+
Cl-
most solutes
water follows bc dec. osmolarity in tubule (higher w.p.)

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11
Q

What occurs at the loop of Henle?

A
  • countercurrent flow
  • pump salt out at the top of the thick, ascending loop
  • salt gradient generated
  • lots of mitochondria here in epithelial cells bc pumping activity
  • water leaves at thin descending limb bc interstitial fluid = hyperosmolar (N.B. ascending limb impermeable to water)
  • epithelial cells here have low density of mitochondria bc passive movement
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12
Q

What occurs at the distal convoluted tubule?

A
  • impermeable to water

- salt pumped, so epithelial cells rich in mitochondria

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13
Q

What cells are rich in mitochondria at the collecting duct of the nephron?

A

intercalated cells, whereas principal cells have low mitochondrial

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14
Q

What are the 2 types of nephron?

A
  • superficial/cortical nephron: glomeruli in outer portions of renal cortex, short loops of Henle
  • juxtamedullary nephrons: glomeruli in juxtamedullary region of cortex, long loops extending down into medullary pyramids
  • only 15% of human’s nephrons have long loops
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15
Q

What is the juxtaglomerular apparatus?

A
  • between glomerulus and DISTAL convoluted tubule
  • macula densa (distal convoluted tubule)
  • extraglomerular mesangial cells
  • juxtaglomerular cells (afferent arteriole)
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16
Q

What are the functions of the juxtaglomerular apparatus?

A
  • GFR regulation through tubulo-glomerular feedback mechanism
  • renin secretion for regulating blood pressure
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17
Q

What is glomerular filtration?

A
  • passive process
  • fluid is ‘driven’ through the semipermeable glomerular capillaries into the Bowman’s capsule space by the hydrostatic pressure of the heart
  • the filtration barrier (size and charge dependent)= highly permeable to fluids and small solutes; impermeable to cells and proteins
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18
Q

What features enable glomerular filtration?

A
  • fenestrated endothelium of glomerular capillaries, surrounded by glomerular basement membrane
  • podocytes w/ numerous pseudopodia that interdigitate to form filtration slits
19
Q

What is hydrostatic pressure?

A

a force that compels a fluid to move out of a vessel

fluid exerts this pressure

20
Q

What is oncotic pressure?

A

type of osmotic force exerted on fluids by presence of proteins in blood and tissues

21
Q

What are the participating pressures involved in glomerular filtration?

A
  • blood hydrostatic pressure exerted–> drives fluid into
  • lower oncotic pressure from interstitial fluid bc no proteins vs. there are proteins in blood–> attempts to draw fluid molecules in
  • HPgc drives fluid into primary urine
  • HPbw works against this = -ve pressure
  • πgc of plasma proteins in gc = -ve pressure
22
Q

What is the equation for net ultrafiltration pressure (Puf)?

A

Puf= HPgc - HPbw - πgc

23
Q

What is glomerular filtration rate?

A
  • amount of fluid filtered from the glomeruli into the Bowman’s capsule per unit time (ml/min)
  • sum of filtration rate of all functioning nephrons
  • GFR= Puf X Kf ultrafiltration coefficient (membrane permeability and SA available for filtration)
24
Q

What is a healthy GFR?

A
  • 90-140ml/min in males
  • 90-125ml/min in females
  • a low GFR is the cardinal feature of renal disease–> buildup of excretory products in plasma
25
Q

How do we regulate GFR?

A
  1. myogenic mechanism: arterial pressure inc.–> afferent arteriole stretches–> arteriole contracts to resist stretch–> vessel resistance rises–> blood flow reduces–> GFR stays the same
  2. tubulo-glomerular feedback mechanism: inc./dec. GFR–> inc./dec. NaCl in loop of Henle–> change detected by macula densa–> inc./dec. ATP and adenosine discharged–> afferent arteriole constricts/dilates–> GFR stabilises
26
Q

What is renal clearance?

A 
the number of litres of plasma that are completely cleared of the substance per unit time
C= (U x V)/P 
ml/min
U= conc. of substance in urine
V= rate of urine production
P= conc. of substance in plasma
27
Q

What is the ideal molecule to use to practically determine GFR?

A
  • ideal molecule: inulin
  • plant polysaccharide
  • freely filtered and neither reabsorbed nor secreted
  • not toxic
  • measurable in urine and plasma
    N.B. not found in mammals, so needs to be infused
28
Q

Why is creatinine commonly used to determine GFR?

A
  • waste product from creatine in muscle metabolism, so amount of creatinine released= fairly constant (if muscle mass= constant)
  • if renal function is stable–> creatinine amount in urine is stable bc freely filtered and not reabsorbed (BUT a small amount is secreted)
  • high plasma creatinine/ low creatinine clearance may indicate renal failure
29
Q

What substance do we use to measure renal plasma flow (RPF)?

A

PAH (para aminohippurate) bc all is removed from plasma passing through kidney by filtration and secretion

30
Q

What is the filtration fraction (FF)?

A

the ratio of the amount of plasma which is filtered and which arrives via the afferent arteriole

  • 0.15-0.20 (15/20% of plasma has been filtered)
  • FF= GFR/RPF
31
Q

What is 2y active/coupled transport?

A
  • a type of active transport
  • movement of 1 solute down its electrochemical gradient provides energy for the other solute to move against it
  • symport e.g. Na+- glucose symporter
  • antiport e.g. Na+- H+ antiporter
32
Q

What is a paracellular pathway?

A
  • transfer of substances across an epithelium by passing through the intercellular space BETWEEN cells (gap junctions)
  • water moves like this, bringing ions w/ it e.g. Ca2+, K+,Cl-, urea etc…
33
Q

What is a transcellular pathway?

A
  • transfer of water THROUGH cells using aquaporins
  • Na+/K+ ATPase transporter for transcellular Na+ reabsorption (bc 3 sodium out, 2 potassium in)–> leads to downhill movement of sodium coupled to other things
34
Q

How are sodium and bicarbonate reabsorbed in the early proximal convoluted tubule?

A

carbonic anhydrase converts H+ and HCO3—> CO2+H20–> then back in cell–> H+ brings a sodium in w/ Na+ H+ antiporter–> Na+ and HCO3- move out into blood w/ symporter

35
Q

What is 100% reabsorbed in the PCT?

A

glucose

36
Q

How does angiotensin regulate Na+ reabsorption in the PCT?

A

increases the number of Na+- H+ antiporters

37
Q

How is glucose reabsorbed in the early proximal convoluted tubule?

A
  • Na+ - glucose symporter brings in sodium and glucose (bc low sodium in cell due to Na+/K+ ATPase pump)
  • glucose then dissolves from cell through GLUT2 transporter into blood down gradient
38
Q

How are Na+ and Cl- actively pumped/reabsorbed in the loop of Henle?

A
  • at thick ascending limb (vs. passively moved in thin ascending limb)
  • Na+ K+ 2Cl- symporter into cell and K+ Cl- symporter out into blood
  • cations Na+, Ca2+ etc… reabsorbed by paracellular pathway
39
Q

How are Na+ and Cl- reabsorbed in the early distal convoluted tubule?

A
  • Na+ Cl- symporter (dependent on Na+/K+ ATPase pump) and K+ Cl- symporter out into blood
40
Q

How is Ca2+ actively reabsorbed at the distal convoluted tubule?

A
  • Na+ Ca2+ antiporter bring sodium into cell (bc Na+/K+ ATPase pump takes sodium out) and Ca2+ goes into blood
41
Q

How does ADH regulate water reabsorption at the distal DCT and collecting duct?

A

causes aquaporins to move to membrane–> inc. water reabsorption

42
Q

How does aldosterone increase sodium reabsorption at the collecting ducts?

A

increases apical Na+ channels and basolateral Na+K+ ATPase pumps

43
Q

How doe we maintain acid-base balance in the collecting ducts?

A
  • alpha intercalated cells: HCO3- reabsorption and H+ secretion
  • beta intercalated cells: HCO3- secretion and H+ reabsorption

BRS Term 2 (36 decks)

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