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biology 153 > urinary system (physiology) > Flashcards

urinary system (physiology) Flashcards

1
Q

how is urine formed?

A

by filtering blood, approximately 1.2 L per day

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2
Q

normal components of urine?

A

95% water

5% solutes- electrolytes, urobilin, hormones, nitrogenous waste (urea, creatinine, uric acid)

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3
Q

abnormal components of urine?

A
  • glucose (glycosuria)
  • proteins (albuminuria)
  • ketones (ketonuria)
  • blood cells (hematuria)
  • bile pigments (bilirubinuria)
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4
Q

what are the 3 steps of urine formation?

A
  1. glomerular filtration
  2. tubular reabsorption
  3. tubular secretion
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5
Q

what is glomerular filtration?

A

-hydrostatic pressure in glomerular capsule forces a filtrate of blood into the glomerular capsule

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6
Q

what is filtrate?

A

water, urea, uric acid, creatinine, electrolytes, nutrients

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7
Q

filtrate contains everything in plasma EXCEPT?

A

blood cells and proteins

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8
Q

filtration occurs where?

A

across the filtration membrane

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9
Q

what is the filtration membrane?

A

membrane of renal corpuscle that filters blood to form filtrate
-formed from endothelium of fenestrated capillaries + basement membrane + podocytes of glomerular capsule

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10
Q

podocytes in filtration membrane?

A

wrap their feet (pedicels) around capillaries

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11
Q

the filtrate moves through the pores of ____?

A

capillaries, across basement membrane and through filtration slits between pedicels

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12
Q

what is GFR?

A

glomerular filtration rate= volume of filtrate formed per min

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13
Q

what is GFR affected by?

A

renal blood pressure

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14
Q

for GFR to occur, what must happen?

A

glomerular hydrostatic pressure (GHP) must be greater than > capsular hydrostatic pressure (CsHP) + blood colloid pressure (BCOP)

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15
Q

how is glomerular filtration regulated?

A

by regulating renal blood pressure and blood flow

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16
Q

what are the 3 main mechanisms of regulation of GF?

A
  1. autoregulation
  2. neural regulation
  3. hormonal regulation
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17
Q

what is autoregulation?

A

kidneys adjust its own BP and blood flow to maintain GFR

-efferent arteriole diameter is < afferent to maintain pressure

18
Q

what is the myogenic mechanism of autoregulation?

A

smooth muscle contracts when stretched and relaxes when not stretched
-decreased BP–> decreased GFR —> decreased stretch so relaxation of smooth muscle —> vasodilation of afferent arteriole —-> increased GFR

19
Q

tubular mechanism of autoregulation?

A 
macula densa (modified epithelial cells in DCT that monitor Na+ concentration in filtrate) release chemicals that cause vasoconstriction when Na+ conc is high 
-increased GFR---> increased Na+----> vasoconstriction of afferent arteriole ----> decreased GFR
20
Q

what is neural regulation (from ANS)?

A

-flight/flight/fight/vigorous exercise diverts blood to muscle
-blood loss diverts blood to heart/brain
so…
ANS—> release norepinephrine —-> vasoconstriction of afferent arteriole —> decreased blood flow to kidney, decreased GFR

21
Q

what is hormonal regulation (RAAS)?

A

renin angiotension aldosterone system

  • involves juxtaglomerular complex
  • macula densa (modified epithelial cells in DC monitor Na+ conc) and JG cells (modified smooth muscle cels in afferent arteriole secrete renin and monitor pressure)
22
Q

what is tubular reabsorption?

A

reabsorption of substances in filtrate back into blood

23
Q

where is most reabsorption?

A

PCT; cuboidal epithelium has microvilli with large surface area

24
Q

reabsorption has 4 main ways?

A
  1. active transport (Na+)
  2. facilitated transport (glucose, amino acids, vitamins)
  3. cotransport with Na+ and diffusion (electrolytes), down chemical gradients
  4. osmosis- water
25
where does reabsorption occur besides the PCT?
nephron loop, DCT, collecting ducts
26
hormones that affect tubular reabsorption?
parathyroid hormone increases calcium reabsorption from DCT | aldosterone increases sodium reabsorption from DCT
27
what is a transport maximum?
occurs for every substance, if renal threshold (plasma concentration at which carriers become saturated) is exceeded, substances normally reabsorbed will appear in urine
28
what is tubular secretion?
secretion of substances from peritubular blood into tubular filtrate (removal of undesirable solutes)
29
where does active transport of 'waste' into filtrate occur in tubular secretion?
along renal tubule
30
what is obligatory water reabsorption (urine concentration)?
-water follows solute, 85% recovery this way
31
what is facultative water reabsorption (urine concentration)?
can recover up to 99% of water to produce very concentrated urine
32
why does concentration of urine happen? (3 components)
1. the medullary gradient 2. countercurrent mechanism 3. ADH
33
what is the medullary gradient?
progressive increase in solute concentration in interstitial fluid from cortex--> medulla -gradient is due to active transport of sodium and chloride out of ascending nephron loops of juxtamedullary nephrons and diffusion of urea from collecting ducts
34
what are the countercurrent mechanisms?
flow of fluids in opposite directions - blood in vasa recta flows in opposite direction to filtrate - filtrate in descending loop flows in opposite direction of filtrate in ascending loop
35
the opposite direction of flow maintains?
establishes and maintains the medullary gradient and enhances reabsorption of water
36
what is the descending loop like?
- thin, water permeable | - water leaves due to the medullary gradient
37
what is the ascending loop like?
- thick, impermeable to water | - NaCl actively transported out (creating medullary gradient)
38
what is ADH? where is it produced, stored? causes what?
antidiuretic hormone or vasopressin - peptide hormone produced in hypothalamus, stored in posterior pituitary - causes aquaporins to appear in collecting ducts (makes permeable to water), h20 leaves filtrate - concentrates urine!
39
well hydrated & ADH?
decreases ADH, duct is impermeable, no water leaves, dilute urine
40
dehydrated & ADH?
increases ADH, duct is permeable, water leaves filtrate, concentrated urine

biology 153 (17 decks)

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