Tubular Reabsorption and Tubular Secretion Flashcards

1
Q

tubular reabsorption

A

returns filtered water and filtered solutes back to the bloodstream

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2
Q

interstitial fluid pressure

A

helps drive water back into peritubular capillaries

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3
Q

blood hydrostatic pressure

A

relatively low in the peritubular capillaries, which reduces resistance to reabsorption

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4
Q

plasma proteins are not filtered

A

which raises blood colloid osmotic pressure in peritubular capillaries

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5
Q

total plasma volume filters through the renal tubules every

A

22 minutes

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6
Q

substances can be reabsorbed from the filtrate along

A

one of two possible routes

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7
Q

transcellular route

A

allows substances to pass from filtrate across epithelial cells of tubule through cytoplasm, into interstitial fluid

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8
Q

paracellular route

A

allows substances to “leak” out of filtrate through “tight” junctions between epithelial cells

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9
Q

substances that get reabsorbed from the filtrate

A

are taken into the peritubular capillaries

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10
Q

blood retains its plasma proteins

A

so water gets drawn into capillaries by osmosis

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11
Q

solvent drag

A

occurs when dissolved solutes enter capillaries by following water

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12
Q

primary active transport

A

uses ATP energy to pump substances into capillaries

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13
Q

secondary active transport

A

uses energy from ionic electrochemical gradient to pump substances into capillaries

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14
Q

symporters

A

can move two or more substances across a membrane in same direction

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15
Q

antiporters

A

can move two or more substances across a membrane in opposite directions

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16
Q

transport maximum (Tmax)

A

describes the reabsorption limit of a renal tubule due to the number of transport proteins that are available

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17
Q

each particular solute has its own Tmax when

A

all of its transporters are occupied

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18
Q

Tmax is high for glucose and

A

other substances that body needs to retain

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19
Q

tubular secretion

A

removes substances form the peritubular capillaries and adds them to the filtrate

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20
Q

most tubular reabsorption occurs in the

A

proximal convoluted tubule

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21
Q

sodium reabsorption creates an

A

osmotic gradient and an electrical gradient to drive the reabsorption of water and other solutes

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22
Q

sodium ions reabsorbed by symporters

A

in first portion of PCT along with glucose, amino acids, phosphate ions

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23
Q

sodium ions reabsorbed by antiporters

A

that transport hydrogen ions out

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24
Q

most abundant cations in filtrate

A

sodium ions

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25
Q

chloride ions get reabsrobed

A

because they follow sodium ions due to electrical attraction

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26
Q

water reabsorption

A

raises chloride concentration in tubular fluid and creates a chloride gradient

27
Q

bicarbonate ions seem to be

A

reabsorbed from the filtrate, but they really aren’t

28
Q

bicarbonate ions are filtered out of the blood

A

but urine is usually free of bicarbonate ions because they do not cross membrane of proximal convoluted tubule

29
Q

bicarbonate ions combine with hydrogen ions

A

present in tubular fluid to form carbonic acid; dissociates into water and carbon dioxide

30
Q

carbon dioxide

A

enters tubule cells and combines with water to again form carbonic acid; dissociates into bicarbnate and hydrogen ions

31
Q

bicarbonate ions are pumped

A

into the blood, and hydrogen ions are pumped back into tubular fluid

32
Q

one bicarbonate ion disappears from the tubular fluid as

A

another appears in the blood

33
Q

glucose is co-transported with sodium ions by

A

sodium-glucose transport proteins

34
Q

glycosuria

A

occurs when excess glucose remains in urine because glucose is not reabsorbed fast enough by symporters

35
Q

nitrogenous wastes

A

are reabsorbed into the capillaries

36
Q

urea

A

40% to 60% of urea formed gets reabsorbed along with water

37
Q

uric acid

A

almost all uric acid gets reabsorbed, but some will be secreted back into tubular fluid later

38
Q

creatinine

A

not reabsorbed at all because it is too lareg

39
Q

water gets reabsorbed into the peritubular capillaries by

A

obligatory water reabsorption

40
Q

about 2/3 of water

A

is reabsorbed through aquaporins in PCT

41
Q

reabsorption of sodium ions and chloride ions and other solutes makes

A

tissue fluid hypertonic to tubular fluid

42
Q

because the PCT reabsorbs proportionate amounts of water and solutes

A

osmolarity of tubular fluid remains relatively constant

43
Q

tubular secretion in the PCT

A

extracts urea, uric acid, ammonia, and other wastes from the blood and transfer them into the tubular fluid

44
Q

secretion of uric acid

A

compensates for its reabsorption and accounts for its presence in urine

45
Q

aspirin, penicillin, and other drugs are

A

secreted into tubular fluid and cleared from the blood

46
Q

bicarbonate ions and hydrogen ions are

A

secreted into tubular fluid to regulate pH of body fluids

47
Q

primary function of the Nephron Loop (of Henle)

A

to create a gradient for urine concentration and water conservation

48
Q

tubular fluid in the nephron loop

A

quite different from glomerular filtrate and blood plasma, because glucose and other solutes have been reabsorbed

49
Q

the descending limb of the nephron loop

A

will reabsorb about 15% of the water present in the glomerular filtrate

50
Q

the thick ascending limb of the nephron loop

A

has symporters that will reabsorb one sodium ion, one potassium ion, and two chloride ions from the tubular fluid

51
Q

potassium ions

A

re-enter tubular fluid, but sodium ions and chloride ions remain in tissue fluid of renal medulla

52
Q

ascending limb

A

is impermeable to water; osmolarity of tubular fluid decreases as tubular fluid flows through it toward distal convoluted tubule

53
Q

sodium ions and chloride ions get reabsorbed by ___________, but the _________ _____________ __________ is relatively impermeable to water

A

symporters; distal convoluted tubule

54
Q

principal cells in the collecting duct

A

reaborb sodium ions and secrete potassium ions

55
Q

intercalated cells in the collecting duct

A

reabsorb potassium ions and bicarbonate ions, but secrete hydrogen ions

56
Q

“proton pumps”

A

so effective at secreting hydrogen ions that urine can be 1000 times more acidic than blood, thereby maintaining pH of body fluids

57
Q

aldosterone

A

secreted by the adrenal cortex when blood levels of sodium fall or when blood levels or potassium rise, causing the DCT and the collecting duct to reabsrobe more sodium ions and secrete more potassium ions

58
Q

chloride ions and water

A

follow sodium ions, which reduces urine volume; salt balance is maintained

59
Q

aldosterone targets principal cells

A

causing them to open so very little sodium leaves urine

60
Q

the increase in blood pressure that results from increased blood volume

A

triggers the release of atrial natriuretic peptide form the heart

61
Q

effects of ANP (atrial natriuretic peptide)

A
  • increases glomerular filtration rate,
  • suppresses the release of ADH by pituitary gland,
  • suppresses release of aldosterone by counteracting effects of angiotensin II
  • inhibits reabsorption of sodium ions by collecting ducts in renal medulla
62
Q

antidiuretic hormone

A

makes the collecting ducts more permeable to water, thereby increasing the reabsorption of water into the tissue fluid and the bloodstream

63
Q

ADH inserts

A

aquaporins into the membranes of principal cells in the collecting ducts