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elimination and detox - wk 2 > renal physiology pt 1 (and small add on from thursday) > Flashcards

renal physiology pt 1 (and small add on from thursday) Flashcards

1
Q

what is filtration

A

conversion of blood plasma into primary tubular fluid, glomerular filtrate

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2
Q

where does filtration occur

A

in the glomerulus, which is a network of capillaries

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3
Q

the driving hydrostatic pressure of filtration in the glomerulus is controlled by:

A

the afferent and efferent arterioles and provided by arterial pressure

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4
Q

what is the golumerular filtration rate (GFR)

A

about 20% of renal plasma is filtered each minute

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5
Q

forces of filtration (2)

A

hydrostatic pressure and oncotic pressure

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6
Q

what is PGC

A

hydrostatic pressure in the glomerular capillary

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7
Q

what is PBS(Pt)

A

hydrostatic pressure in the bowmans space - nonexistent in healthy animals

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8
Q

what is ||GC

A

oncotic pressure in the glomerular capillary

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9
Q

what is ||BS

A

oncotic pressure in the bowmans space - minimal in healthy animals

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10
Q

what determines the hydrostatis pressure in the glomerular capillary and what does it determine

A
  • it determines the rate of filtration as well of the tubular fluids/urine flow to renal pelvis
  • determined by blood input from afferent arterioles and tonus of efferent arterioles
  • primary target of regulatory mechanisms that control GFR
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11
Q

what is plasma oncotic pressure determined by

A

difference of protein concentrations between blood plasma and glomerular filtrate

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12
Q

is plasma oncotic pressure a primary target of regulatory mechanisms that control GFR

A

no

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13
Q

how does plasma oncotic pressure affects the rate of filtration

A

there is a net filtration along the entire length of the glomerular capillaries

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14
Q

hydrostatic pressure in the bowmans space

A
  • BS insignificant for a healthy animal
  • can dramatically rise and prevent filtration upon obstruction of ureters
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15
Q

permeability

A
  • sieve function
  • contributes to the co-efficient of ultrafiltration (Kf) along with filtration surface
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16
Q

what is the co-efficient of ultrafiltration

A

Kf

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17
Q

what are the factors affecting permeability of polypeptides

A
  • size
  • shape
  • charge
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18
Q

how does size affect permeability of polypeptides

A

proteins the size of plasma albumins or larger are not efficiently filtered compared to smaller peptides

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19
Q

how does shape affect permeability of polypeptides

A

long flexible proteins are filtered more efficient than globular proteins

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20
Q

how does charge affect permeability of polypeptides

A

positively charged polypeptides are filtered more efficiently than negatively charged molecules

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21
Q

what is renin

A

a polypeptide hormone, produced by specialized cells of the wall of the afferent arteriole (JG cells)

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22
Q

what is the release of renin stimulated by

A

a decrease in renal perfusion

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23
Q

what is angiotensin II

A

potent peptide vasoconstrictor that acts directly and indirectly

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24
Q

how does angiotensin II act directly

A

contricts arterial blood vessels to increase systemic blood pressure and renal perfusion pressure

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25
Q

how does angiotensin II act indirectly

A

stimulates the release of:
* the mineralocorticoid steroud hormone aldosterone from the adrenal gland
* polypeptide hormone vasopressin (ADH, anti-diuretic hormone) from the pituitary gland

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26
Q

what stops vasocontriction

A

NO

PgE2
PgI2

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27
Q

what is the relationship between glomerular arteriolar resisitance, GFP and renal plasma flow (RPF)

A
  • constriction of the afferent
  • contriction of the efferent
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28
Q

what does contriction of the afferent do

A

arteriole increases renal vascular resistance (therby reducing RPF) and decreases the intraglomular pressure and GFR

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29
Q

what does constriction of the efferent do

A

arteriole also lowers RPF but tends to elevate the intraglomerular pressure and GFR

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30
Q

the intrarenal pressure distal to stenosis should be lower than the arterial pressure. as a result, lowering systemic blood pressure AND preventing ability of AII to compensate for that by constricting the efferent arteriole can dramatically decrease GFR and may lead to:

A

acute renal failure

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31
Q

within the kidney itself, there are mechanisms that directly control the glomerular capillary perfusion (2)

A
  • myogenic reflex
  • tubulo-glomerular feedback
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32
Q

which intrinsic factor regulating GFR is independent of renal innervations but might be influenced by levels of prostaglandings and NO

A

myogenic reflex

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33
Q

what is the myogenic reflex

A
  • glomerular arterioles respond to changes in arteriolar wall tension
  • immediate arteriolar constriction in response to an increase in this wall tenstion
  • a decrease in arteriolar wall tension results in virtually immediate arteriole dilation
34
Q

what is the macula densa

A

a morphologically distinct cluster of epithelial cells, located in the distal portion of the thick ascending limb of the loop of henle

35
Q

what are macula densa cells sensitive to

A

an increase in the tubular flow rate

36
Q

what does an increase in tubular flow rate lead to

A

decrease in the filtration rate of glomerulus of the same nephron by yet poorly characterized mechanism

37
Q

what is inulin

A
  • a zenobiotic
  • an indicator substance of choice because the rate of its disappearance from plasma strictly relates to the rate of GFR
38
Q

in clinical practice, the most widely used indicator substance to measure GFR is

A

creatinine

39
Q

what is creatinine

A

a byproduct of muscle metabolism that is handled by kidney similarly to inulin

40
Q

what test is not applicable in birds as avian renal tubules can both secrete and re-absorb it

A

creatinine

41
Q

what is filtration fraction (FF)

A

the fraction of renal plasma flow that is actually filtered by glomeruli

42
Q

what is fractional excretion (FE)

A

the rate of urinary excretion of a substance X divided by its rate of filtration

43
Q

when creatinine does not help much you can use

A

BUN: blood urea nitrogen

44
Q

what is GFR directly related to

A

renal mass/number of functional nephrons

45
Q

what is an example of a diverse cause for nephrotic syndrome

A

acute glomerulonephritis

46
Q

what is tubular reabsorption

A

a process where the direction of solute transfer is from tubular lumen to the peritubular capillary plasma

47
Q

what is tubular secretion

A

the opposite direction from the peritubular capillary plasma to tubular lumen

48
Q

what is excretion

A

filtration - reabsorption + secretion

49
Q

how is renal tubule function assessed

A

by determining fractional excretion rate (FER) and fractional re-absorption rate (FAR)

50
Q

what is FER

A

the percent of a filtered substance that is ultimately excreted in the urine

51
Q

what is FAR

A

the proportion of filtered substance X that is reabsorbed by the tubule

52
Q

what is the proximal tubule responsible for

A

the reabsorption of the bulk of filtered solutes

53
Q

anatomo-histologic structure of the proximal tubule facilitates the movement of tubule fluid components inro the blood through two pathways:

A
  1. the trans-cellular pathway
  2. paracellular pathway
54
Q

in the paracellular pathway, substances are reabsorbed through this pathway move from tubular fluid across the:

A

tight junctions

55
Q

what is a tight junction

A

a highly permeable structure, which attaches the cells of epithelial sheet to each other and forms the boundary between the apical and basolateral membranes

56
Q

paracellular transport occurs by passible diffusion or by:

A

solvent drag

57
Q

what is solvent drag

A

a mechanism, which is the entrainment of solute by the flow of water

58
Q

the movement of water and solutes from the interstitial fluid into bloodstream is driven by:

A

starling’s forces

59
Q

much of the transport of substances from the tubular fluid to the blood is driven by:

A

active transport of Na+

60
Q

re-absorption of filtered peptides:

A
  • a large proportion of filtered peptides are degraded to amino acids by peptidases present in the proximal tubule brush border
  • AA are reabsorbed in a co-transport with Na+
61
Q

why are a wide variety of organic ions secreted into tubular fluid in the proximal tubule

A

most of them are bound to proteins in the plasma, these substances are not filtered in the glomerulus, so secretion of these substances in the proximal tubule is the major patheay of their excretion

62
Q

what is an example of an organic ion

A

hippurates

63
Q

what is a veterinary importance of proximal tubular secretion

A

monitoring function of the tubule

64
Q

in clinical practice what is one of the most important parameters of renal function

A

GFR

65
Q

how is GFR determined

A

the rate of clearance of the plasma of a particular substance

66
Q

the active transport systems of reabsorption in the renal tubules can have a limit which is called the:

A

transport maximum (Tmax)

67
Q

what does Tmax reflect

A

the amounts of material that can transport per unit time

68
Q

Tmax of glucose is

A

amount of glucose transported per unity time to saturate the membrane transporters in the proximal tubule

69
Q

Tmax equation

A

GFR X concentration of glucose in ultrafiltrate

70
Q

the segments that include the thick ascending limb of henle and the distal convoluted tubule are very important for reabsorption of:

A

Na+, K+, Cl-, Ca+, and Mg2+

71
Q

the thick ascending limb of the loop of henle and the distal convoluted tubule are able to reabsorb solutes against a

A

high gradient

72
Q

the thick ascending limb of the loop of henle and the distal convoluted tubule exhibit poor:

A

permeability to water

73
Q

what is reabsorbed in the thick ascending loop of henle

A

35-40% of the filtered NaCl

74
Q

what does reabsorption of NaCl in the thick ascending loop of henle allow

A

formation of osmotic gradient in the interstitium and dilution of urine in the tubule

75
Q

what are the 5 mechanisms that drive reabsorption in the distal tubule segments

A
  1. Na+-K+ ATPase in basolateral membrane of the cells actively transports Na+ from the cells into interstitial fluid and creates an electro-chemical gradient for Na+ across the apical membrane
  2. gradient drives Na+, K+, 2Cl- co-trasporter in the apical membrane and these ions move from tubular fluid into the cell
  3. Cl- diffuses down its chemical gradient into the interstitial fluid via Cl- channels in the basolateral membrane
  4. K+ moves extracellularly down its concentation gradient through K+ channels across both basolateral and apical membrane
  5. net result of Cl- absorption and K+ secretion: formation of a lumen-to-blood electrical gradient, that moves cations from tubular fluid to blood through paracellular pathway
76
Q

what is the importance of reabsorption in the distal tubule

A

resulting dilution of tubular fluid allows the kidney to regulate water excretion without loosing salt - prevents water overload and plasma hypotonicity

77
Q

what are the two major cell types of collecting ducts

A
  • principal cells
  • intercalated cells
78
Q

what are intercalated cells involved in

A

K+ and Na+ re-absorption

79
Q

what are principal cells involved in

A

K+ secretion

80
Q

the ultimate rate of renal excretion of K+ and its concentration in the urine is determined by:

A

the efficiency of intercalated cells and principal cells

elimination and detox - wk 2 (5 decks)

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