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biology 153 > urinary system (physiology) > Flashcards

urinary system (physiology) Flashcards

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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
Q

where does reabsorption occur besides the PCT?

A

nephron loop, DCT, collecting ducts

26
Q

hormones that affect tubular reabsorption?

A

parathyroid hormone increases calcium reabsorption from DCT

aldosterone increases sodium reabsorption from DCT

27
Q

what is a transport maximum?

A

occurs for every substance, if renal threshold (plasma concentration at which carriers become saturated) is exceeded, substances normally reabsorbed will appear in urine

28
Q

what is tubular secretion?

A

secretion of substances from peritubular blood into tubular filtrate (removal of undesirable solutes)

29
Q

where does active transport of ‘waste’ into filtrate occur in tubular secretion?

A

along renal tubule

30
Q

what is obligatory water reabsorption (urine concentration)?

A

-water follows solute, 85% recovery this way

31
Q

what is facultative water reabsorption (urine concentration)?

A

can recover up to 99% of water to produce very concentrated urine

32
Q

why does concentration of urine happen? (3 components)

A
  1. the medullary gradient
  2. countercurrent mechanism
  3. ADH
33
Q

what is the medullary gradient?

A

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
Q

what are the countercurrent mechanisms?

A

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
Q

the opposite direction of flow maintains?

A

establishes and maintains the medullary gradient and enhances reabsorption of water

36
Q

what is the descending loop like?

A
  • thin, water permeable

- water leaves due to the medullary gradient

37
Q

what is the ascending loop like?

A
  • thick, impermeable to water

- NaCl actively transported out (creating medullary gradient)

38
Q

what is ADH? where is it produced, stored? causes what?

A

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
Q

well hydrated & ADH?

A

decreases ADH, duct is impermeable, no water leaves, dilute urine

40
Q

dehydrated & ADH?

A

increases ADH, duct is permeable, water leaves filtrate, concentrated urine

biology 153 (17 decks)

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