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Human Physiology > lecture 7: urinary system (excretory system) > Flashcards

lecture 7: urinary system (excretory system) Flashcards

1
Q

why are kidneys important

A

maintain homeostasis

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2
Q

how many functions of the excretory system are there

A

5

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3
Q

name all 5 functions of excretory system

A

excretion
osmoregulation
produces erythropoietin
produces renin
activates vitamin D

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4
Q

describe excretion (functions of excretory system)

A

removal of nitrogenous waste products (urea)

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5
Q

describe osmoregulation (functions of excretory system)

A

regulating solute and water balance
maintains osmotic pressure

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6
Q

describe produces erythropoietin (functions of excretory system)

A

production of rbcs

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7
Q

describe produces renin (functions of excretory system)

A

enzyme that regulates blood pressure by activating angiotensin

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8
Q

which functions of excretory system regulate blood pressure

A

osmoregulation
produce renin

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9
Q

what is urea

A

nitrogenous waste

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10
Q

describe urea

A

made in liver by combining NH3 with CO2
~ 100 000x less toxic than ammonia
can be transported and stored at high concentrations
has a large impact on water balance (osmoregulation)

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11
Q

describe body’s strategy for osmoregulation

A

kidneys —> regulate composition of blood —> regulate composition of ISF —> regulate composition of cells

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12
Q

describe anatomy of urinary system

A

pathway of urine
kidneys —> ureters —> urinary bladder —> urethra

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13
Q

describe urinary bladder

A

stores urine
rugae for stretching
internal urethral sphincter (involuntary)
external urethral sphincter (voluntary)

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14
Q

describe kidneys

A

2 distinct regions =
outer renal cortex
inner renal medulla
contain nephrons and associated blood vessels

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15
Q

describe blood supply to kidneys

A

enters via renal artery and leaves via renal vein
20% of resting cardiac output passed through kidneys every minute
entire plasma volume is filtered 60 times per day

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16
Q

what are kidneys filled with

A

nephrons and collecting ducts are lined by transport epithelium that is specialized to reabsorb water and solutes to control composition of urine

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17
Q

what is a nephron

A

functional unit of kidney

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18
Q

how many nephrons does a kidney contain

A

around 1 million

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19
Q

name the 2 parts of a nephron

A

renal corpuscle
renal tubule

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20
Q

describe renal corpuscle

A

bowman’s capsule (nephron)
glomerular capillaries - glomerulus (stuck to nephron)

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21
Q

describe renal tubule

A

proximal convoluted tubule
nephron loop (loop of henle)
distal convoluted tubule

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22
Q

name the 3 processes of formation of urine

A

glomerular filtration
tubular reabsorption
tubular secretion

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23
Q

describe glomerular filtration (gen)

A

fluid is pushed out of glomerular capillaries into bowman’s capsule
mostly non selective (only depends on size)

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24
Q

describe tubular reabsorption

A

H2O and valuable solutes (glucose, amino acids, some salts) are reabsorbed back into blood
much more selective

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25
Q

describe tubular secretion

A

some solutes are selectively pumped by active transport into the nephron (some salts, H+, drugs)

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26
Q

describe collecting ducts

A

where fluid from nephron drains into
extend into medulla and drain into the renal pelvis (which drains into ureter)

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27
Q

describe pathway of blood supply of nephron

A

heart —> renal artery —> afferent arteriole —> glomerular capillaries —> efferent arteriole —> peritubular capillaries (proximal and distal) —> renal vein OR vasa recta (capillaries, loop of henle) THEN renal vein —> heart

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28
Q

describe exchange path (blood supply of nephrons)

A

via interstitial fluid
blood <—> ISF <—> nephron

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29
Q

when kidneys fail describe what to do (step before transplant)

A

dialysis
several times per week
blood flows out of body and is filtered by external device
you won’t pee
must be very aware about liquid composition

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30
Q

describe filtration (physical description)

A

specialized octopus like cells called podocytes form inner layer of bowman’s capsule and wrap around glomerular capillaries
spaces between foot-processes of podocytes are called filtration slits

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31
Q

describe filtration (specifics of how it works)

A

flow driven by high hydrostatic pressure (blood pressure) in glomerular capillaries
filtration slits act like a sieve that allow the passage of anything below a certain size

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32
Q

what is the composition of filtrate

A

same as blood except no blood cells or proteins

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33
Q

what is filtrate

A

water
salts
sugars
amino acids
nitrogenous waste

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34
Q

why is blood pressure high in glomerular capillaries

A

because the efferent arteriole has a smaller diameter than the afferent arteriole

35
Q

what is reabsorbed from filtrate

A

99% of water
most of glucose, amino acids and vitamins

36
Q

what is initial and final volumes (urinary system)

A

initial filtrate volume = 180L
final urine volume = 1.5L

37
Q

describe what is reabsorbed in proximal tubule

A

NaCl and water
90% of bicarbonate (HCO3-): controls pH
nutrients (glucose, amino acids, etc)
K+

38
Q

describe what is secreted in proximal tubule

A

some drugs and NH3 enter tubules from peritubular capillaries via ISF
H+ (helps control pH)

39
Q

describe loop of henle (descending limb)

A

transport epithelium is permeable to H2O but NOT pet able to NaCl or other solutes
reabsorbs water
filtrate becomes more concentrated

40
Q

describe loop of henle (ascending limb)

A

transport epithelium is NOT permeable to H2O but is permeable to NaCl
NaCl is reabsorbed
filtrate becomes more dilute

41
Q

what can’t pass through the filtration slits

A

blood cells and proteins are too large

42
Q

describe the reabsorption of NaCl and water in proximal tube

A

Na+ is actively transported out of tubule and positive charge is balance by transport of Cl-
water follows by osmosis
65% of volume is reabsorbed

43
Q

describe the reabsorption of NaCl in the loop of henle (ascending limb)

A

as filtrate moves up the thin segment NaCl passively diffuses into ISF
in thick segment NaCl is actively transported into the ISF

44
Q

what is reabsorbed in distal tubule

A

NaCl (actively pumped out to regulate levels in body)
water (reabsorbed passively by osmosis)
HCO3- (controls pH)

45
Q

what is secreted in distal tubule

A

K+ (regulates k+ levels)
H+ (helps control pH)

46
Q

describe collecting duct

A

transport epithelium is permeable to
water
region in inner medulla is also permeable to urea

47
Q

what is reabsorbed in collecting duct

A

NaCl (actively transported across epithelium to regulate levels in body)
water (passively by osmosis, driven by NaCl and urea gradient)

48
Q

describe filtrate in collecting duct

A

filtrate becomes more concentrated as it moves down collecting duct
allows kidneys to excrete hyperosmotic urine and conserve water

49
Q

what is osmolarity

A

concentration of solutes
mOsm/L
for blood = 300mOsm/L

50
Q

why is osmolarity of urine max 1200mOsm/L

A

limited by max concentration of surrounding kidney tissues
max concentration of solutes in inner medulla is 1200mOsm due to NaCl and urea

51
Q

name 2 types of nephrons

A

juxtamedullary nephrons
cortical nephrons

52
Q

describe juxtamedullary nephrons

A

20% of nephrons
loop of henle is long and extends deep into medulla
can create steep osmotic gradient in kidney to produce urine that is hyperosmotic to the body

53
Q

name and briefly describe the 3 steps/parts to creating concentrated urine

A

i - countercurrent multiplier: creates osmotic gradient
ii - countercurrent exchange: preserves osmotic gradient
iii - collecting ducts: adjusts urine osmolarity

54
Q

describe countercurrent multiplier

A

loop of henle
ascending and descending limbs
flow of fluid multiples power of NaCl pumps (pumps out more NaCl)

55
Q

describe countercurrent multiplier (loop of henle - ascending limb)

A

NaCl is pumped out to create osmotic gradient in kidney
filtrate becomes less concentrated as it moves up

56
Q

describe countercurrent multiplier (loop of henle - descending limb)

A

osmotic gradient causes water to leave the filtrate by osmosis
filtrate becomes more concentrated as it moves down

57
Q

describe countercurrent exchange

A

vasa recta - highly permeable to water and solutes
blood flow is very slow to allow enough time for exchange to occur between blood and ISF
blood can deliver nutrients and reabsorb water/solutes without disrupting osmotic gradient in kidney

58
Q

explain countercurrent exchange (exchange between blood and ISF)

A

allows blood to remain isosmotic to ISF
most solutes that move into the blood (as flows downwards) move back out (as flow upwards)

59
Q

describe collecting ducts (creating concentrated urine)

A

adjust osmolarity of urine
nephrons use energy to produce an osmotic gradient in the kidney
NaCl and urea are the primary solutes that create the gradient

60
Q

nephrons using energy to produce osmotic gradient in kidney allows what

A

allows max amount of water to be extracted from urine as it passes through collecting duct

61
Q

describe hormonal control of urine production (gen)

A

composition of urine can be modified based on needs of body
hormones control the osmolarity, salt concentration, volume and hydrostatic pressure of blood

62
Q

name all the hormones that control urine production (4)

A

ADH (antidiuretic hormone)
angiotensin II (RAAS)
aldosterone (RAAS)
ANF (atrial natriuretic factor)

63
Q

name the hormones that cause water retention

A

ADH
angiotensin II
aldosterone

64
Q

name the hormones that cause water loss

A

ANF

65
Q

describe ADH (site of production, target and effect)

A

s - hypothalamus (stores/released by pituitary gland)
t - epithelium of distal tubule and collecting duct
e - increase permeability to H2O (increase reabsorption)

66
Q

name the stimuli that could cause hormone to change something about the urine

A

changes in blood pressure
changes in blood osmolarity

67
Q

describe angiotensin II (site of production, target and effect)

A

s - liver (activated by renin, a kidney enzyme)
t - arterioles, proximal tubule, adrenal glands
e - vasoconstriction, increase NaCl reabsorption (H2O follows), aldosterone production

68
Q

describe aldosterone (site of production, target and effect)

A

s - adrenal glands
t - distal tubules
e - increase NaCl reabsorption (H2O follows)

69
Q

describe ANF (site of production, target and effect)

A

s - walls of atria
t - kidney, collecting ducts, adrenal glands
e - inhibits renin release, inhibits NaCl reabsorption, inhibits aldosterone release

70
Q

describe ADH

A

osmoreceptors in hypothalamus are stimulated when blood rises above 300mOsm/L (set point)
causes more ADH to be released into blood
ADH increases H2O reabsorption at distal tubule and collecting duct to decrease urine volume

71
Q

what can bring osmolarity back to set point

A

ONLY intake of water can bring osmolarity back to set point
ADH only prevents further increase above set point

72
Q

ADH is an example of what type of feedback

A

negative

73
Q

how does ADH work

A

increases H2O reabsorption by incresing number of aquaporins in collecting duct epithelium
aquaporins are integral membrane proteins that allow passage of water by facilitated diffusion

74
Q

what does RAAS stand for

A

renin-angiotensin-aldosterone system

75
Q

describe RAAS (3 steps/statements)

A

i - renin is an enzyme that initiates chemical reactions to convert angiotensin into angiotensin II
ii - angiotensin II is a hormone that increases blood volume and pressure
iii - aldosterone is a hormone that is released by adrenal gland (stimulated by angiotensin II)

76
Q

describe angiotensin II

A

drop in blood pressure triggers release of renin in JGA
angiotensin II increases blood volume and pressure

77
Q

how does angiotensin II increase blood volume and pressure

A

vasoconstriction of arterioles
increase NaCl reabsorption (H2O follows) in proximal tubule
stimulating release of aldosterone

78
Q

what does JGA stand for

A

juxtaglomerular apparatus (in kidney)

79
Q

describe aldosterone

A

increase NaCl reabsorption (H2O follows) in distal tubules
released from adrenal glands (endocrine glands on top of kidneys)

80
Q

describe ANF

A

released by walls of atria in response to high blood volume and pressure
opposes the RAAS mechanism to lower blood pressure and volume

81
Q

what does ANF inhibit

A

renin release
aldosterone release
reabsorption of NaCl in collecting ducts

82
Q

what effect does alcohol have on urine

A

alcohol inhibits ADH (ADH - lowers urine production) so alcohol increases urine production

83
Q

excessive water loss or inadequate intake of water causes dehydration

A

stimuli = increases osmolarity and decreases blood pressure
response = ADH & RAAS

84
Q

excessive loss of body fluids (water and salts) due to blood loss or diarrhea

A

stimuli = decreases blood pressure
response = RAAS

Human Physiology (17 decks)

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