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Renal > Physiology > Flashcards

Physiology Flashcards

1
Q

what is osmolarity

A

concentration of osmotically active particles present in a solution

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2
Q

what are the units of osmolarity

A

osmol/l or mosmol/L (for body fluids as weaker)

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3
Q

how can you calculate osmolarity

A

the molar concentration of the solution x
the number of osmotically active particles present

e.g. 150mM NaCL = 2 x 150m = 300 mosmol/l

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4
Q

what is the units for osmolality

A

osmol/kg

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5
Q

what is tonicity

A

the effect ta solution has on cell volume

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6
Q

what is a isotonic solution

A

a solution that causes no change in cell volume, there is no net movement of water

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7
Q

what is a hypotonic solution

A

solution that causes an increase in cell volume, water moves into cell by osmosis, more water initially outside of the cell
(more water)

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8
Q

what is a hypertonic solution

A

causes a decrease in cell volume, cell loses fluid as initially less water in external environment
(less water, concentrated salt solution)

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9
Q

what can happen if a cell expands with water too much

A

lysis

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10
Q

what is hydrostatic pressure

A

pressure created by fluid- high hydrostatic will push water into lower hydrostatic pressures

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11
Q

what osmolarity are isotonic solutions usually

A

300 mosmol/l
less than 300= hypotonic
more than 300= hypertonic

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12
Q

what other that osmolarity affects tonicity

A

the permeability of the membrane (ability of solute to cross the cell membrane)
e.g. 300 mM or urea will be hypotonic as RBC have transporters for this and leave more water outside the cell

300 mM of sucrose is isotonic as RBC membrane not permeable to this

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13
Q

what is the osmolairty of plasma and extracellular fluid

A

300 mosmol/l

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14
Q

do male or females have more body water

A

males

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15
Q

what are the 2 main compartments of total blody water

A 
intracellular fluid (67%)
extracellular fluid (33%)
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16
Q

what makes up extracellular fluid

A

plasma (20%) (liquid component of blood)
interstitial fluid (80%)
lymph (negligible) and transcellular fluid (negligible)

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17
Q

what makes up transcellular fluid

A

CFS and pleural fluid

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18
Q

how can you measure body fluid

A

tracers can show the distribution volume (allow it to equilibrate with body water then take sample and measure its concentration)
TBW- 3H2O
ECF- inulin
plasma- labelled albumin

(dose/ sample concentration= volume of distribution)

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19
Q

what are the fluid inputs

A

fluid intake
food intake
metabolism

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20
Q

what are the fluid outputs

A 
insensible loss (not controllable) (skin diffusion, lung exhalation) 
sensible loss (controllable) (sweat, faeces, urine)
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21
Q

what is water imbalance mainfested as

A

changes in body fluid osmolarity

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22
Q

what is the normal rate of urine production

A

1ml/min

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23
Q

what does a change in plasma volume affect

A

arterial BP

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24
Q

what happens to lung water loss when its cold

A

increases

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25
Q

can you completely turn off urine production

A

no as some waste products can only be excreted in solution

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26
Q

what is the ionic composition of ECF

A

high Na+
high Cl-
high bicarbonate (HCO3-)

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27
Q

what is the ionic composition of ICF

A

high potassium
high Mg2+
negatively charged proteins

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28
Q

what fluids have similar ionic composition

A

plasma and intersitial fluid

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29
Q

what is the ionic composition of plasma

A

high Na+

high Cl+

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30
Q

what separates ECF and ICF

A

plasma membrane

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31
Q

are the osmotic concentrations of ECF and ICF the same/ different

A

identical- 300 mosmol/l

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32
Q

what is fluid shift

A

movement of water betweem the ICF and ECF in response to an osmotic gradient

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33
Q

what would happen if the osmotic concentration of the ECF increases

A

ECF would become hypertonic meaning water would be lost from the ICF

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34
Q

what would happen if the osmotic concentration of the ECF decreases

A

ECF is now hypotonic so water would go into the ICF

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35
Q

what happens to the volumes of ICF and ECF when there is a loss or gain of NaCl in the ECF

A

(Na excluded from)

ECF NaCl gain= ECF increased, ICF decreases (water leaves)

ECF NaCl loss= ECF decreased, ICF increased (ECF hypotonic)

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36
Q

what are the challenges to fluid homeostasis

A

gain or loss of water- changes fluid osmolarity

gain or loss of NaCl- ^same

gain or loss of isotonic fluid (e.g. saline= 0.9% NaCl)
no change in osmolarity but change in ECF volume ONLY

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37
Q

what alters composition and volume of the ECF

A

kidneys

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38
Q

why is regulation of ECF volume important

A

for long term regulation of blood pressure

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39
Q

what is electrolyte balance

A

when rate of gain= rate of loss

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40
Q

why is electrolyte imbalance important

A

concentrations can affect water balance (via changes in omsolarity)
concentrations can affect cell function

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41
Q

what creates 90% of the ECF’s osmotic concentration

A

sodium salts (as this is mainly present in the ECF is a major determinant of ECF volume)

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42
Q

what follows sodium

A

water

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43
Q

what affects sodium reabsorbtion in the kidneys

A

aldosterone

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44
Q

what is a key role of potassium

A

establishing membrane potential

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45
Q

is potassium intracellular or extracellular

A

intracellular

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46
Q

what can fluctuations in the concentration of plasma potassium cause

A

muscle weakness, paralysis, cardiac arrhythmias, cardiac arrest

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47
Q

where do you lose salt

A

sweat and faeces 0.5 g

urine 10 g

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48
Q

what is salt imbalance manifested as

A

changes in extracellular fluid volume

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49
Q

what are the functions of the kidneys

A 
water and salt balance
maintain plasma volume and osmolarity 
acid base balance 
excretion of metabolic waste and exogenous compounds 
secretion of renin and erythopoietin
conversion of vit D into clcitriol
50
Q

what is the active form of vit D and its role

A

calcitriol- calcium absorption in the GI tract

51
Q

what controls the conversion of vit d to calcitriol

A

parathryoid hormone

52
Q

when is erythropoietin release

A

when hypoxic- stimulates RBC production

53
Q

what muscles line the ureters

A

smooth muscles- peristaltic action to push urine down to baldder- colicky pain

54
Q

does the urine get modified when it enters the ureter

A

no- same as when leaves bladder

55
Q

what is the ‘appearance’ of the inside of the kidney

A

cortex is granular

medulla is striated

56
Q

what is the functional unit of the kidney

A

the nephron

57
Q

what are the functions of the nephron

A 
filtration 
reabsorption (move things back into the blood)
secretion (move from blood into tubular fluid)
58
Q

what makes up the wall of the nephrons

A

single layer of epithelial cells

59
Q

describe the blood supply of a cortical nephron (80% of the nephrons)

A

renal artery- afferent artery- glomerulus- efferent arteriole- pertibular capillary (meshwork closely related to the tubular component of nephron)- venules- renal vein

60
Q

what supplies the tubular nephron and secretes/ recieves reabsorbed particles

A

peritublar capillaries

61
Q

where does the collect duct start and end

A

starts in cortex, goes through medulla connecting with proximal tubules, ends in renal pelvis

62
Q

what is the fluid in the nephron called

A

tubular fluid (still being modified- when it enters collecting duct=urine)

63
Q

what are the parts of the nephron

A

bowmans capsule- proximal tubule- descending then ascending limb of loop of henle- distal tubule- collecting duct

64
Q

describe the blood supply of a juxtamedullary nephron

A

single capillary (vasa recta) which follows the route taken by the loop of henle

65
Q

which type of nephron has a bigger loop of henle

A

juxtamedullary

66
Q

what creates the striated appearance of the medulla

A

the loops of henle ad the collecting ducts (as arranged in a radial fashion)

67
Q

does the afferent or efferent artery have a bigger diameter

A

afferent bigger- maintains pressure

68
Q

what muscles line the afferent arterioles

A

smooth- contraction reduces the amount of blood that flows into the glomerulus

69
Q

what makes up the glomerular membrane

A

capillary endothelium
basal lamina
podocytes

70
Q

what are the roles of the juxtaglomerular aparatus

A

macula densa cells are salt sensitive- monitor salt in tubular fluid

granular cells produce and secrete renin

71
Q

what is urine

A

modified filtrate of blood

72
Q

what are the renal processes

A

glomerular filtration

tubular reabsorption and secretion

73
Q

how much of plasma that enters the glomerulus is filtered

A

20%

74
Q

what does rate of excretion=

A

rate of filtration + rate of secretion - rate of reabsorption

75
Q

what does rate of filtration =

A

concentration of X in plasma x GFR

76
Q

what is a healthy GFR

A

125 ml/min

77
Q

what does rate of excretion =

A

concentration of x in urine x volume of urine produced

78
Q

what does rate of reabsorption =

A

rate of of filtration of X - rate of excretion of X

79
Q

what does rate of secretion =

A

rate of excretion of X - rate of filtration of X

80
Q

what must have happened if rate of filtration > rate of excretion

A

net reabsorbtion

81
Q

what are the filtration barriers

A 
Glomerular Capillary Endothelium (barrier to RBC)
Basement Membrane (basal lamina) (plasma protein barrier) 
Slit processes of podocytes (plasma protein barrier)
(Glomerular epithelium)
82
Q

what makes up the basement membrane

A

collagen and glycoprotein

83
Q

why cant plasma proteins cross the basement membrane

A

as plasma proteins are negatively and so too is the basement membrane

84
Q

should RBC get through into the lumen on bowens capsule

A

no- if RBCs in urine then something is wrong

85
Q

what forces make up the net filtration pressure

A

glomerular capillary blood pressure (largest: 55mmHg)
bowmans capsule oncotic pressure (0 as no plasma proteins in bowens)

bowmans capsule hydrostatic pressure (fluid within capsule- opposes net filtration)
capillary oncotic pressure (plasma proteins within lumen pull water back into capillaries opposing net filtration)

86
Q

is filtration active or passive

A

passive- driven by net filtration pressure

87
Q

how can glomerulae capillary pressure remain constant across the capillary

A

as efferent diameter smaller than afferent

88
Q

what is the usual net filtration pressure

A

10mm Hg

89
Q

what are starling forces

A

the balance of hydrostatic pressure and osmotic (oncotic) pressures

90
Q

what is GFR

A

rate a which protein free plasma is filtered from the glomeruli into bowmans per unit time

= Kf (filtration coefficient- how permeable the glomerular membrane is) x net filtration pressure

91
Q

what is the major determinant of GFR

A

glomerular capillary fluid pressure

92
Q

what is the extrinsic control of GFR

A

sympathetic control via baroreceptor reflex

93
Q

what is the intrinsic control of GFR

A

autoregulation:
myogenic
tubuloglomerular feedback mechanism

94
Q

how does arterial blood flow affect GFR

A

if increases causes increased net filtration pressure, increasing GFR (opposite applies)

vasoconstriction of smooth muscles of afferent arterioles decreases blood supply to glomerulus, decreasing GFR

vasodilation of afferent ateriole increases blood flow, increasing GFR

95
Q

how is GFR controlled by changes in arterial blood pressure

A 
e.g 
fall in blood volume 
decreased ABP
detected by aortic and carotid sinus baroreceptors 
increased sympathetic activity
arteriolar vasoconstriction 
decreased glomerular blood flow 
decreased GFR
decreased urine volume 
helps compensate for lack of blood
96
Q

what allows the GFR to remain fairly constant despite MABG

A

autoregulation- intrinsic control

myogenic and tubuloglomerular feedback

97
Q

what is myogenic intrinsic control

A

if vascular smooth muscle is stretched (increased ABP) then it contracts constricting the arteriole
aims to maintain constant blood flow to the kidneys

98
Q

what is tubuloglomerular feedback

A

involves the juxtaglomerular apparatus (macula densa cells- release vasoactive substances)
if GFR rises more NaCl flows through the tubule leading to the constriction of afferent arterioles
this decreases blood flow and decreases GFR

99
Q

what senses the NaCl content of the tubular fluid

A

macula densa cells in the juxtaglomerular apparatus

100
Q

what cause cause increased bowmans capsule fluid pressure

A

e.g. kidney stone, blockage in drainage

101
Q

what cause cause increased capillary oncotic pressure

A

diarrhoea (losing water but not plasma proteins)

102
Q

what cause cause decreased capillary oncotic pressure

A

severe burns (losing plasma proteins but not water)

103
Q

what can decrease the filtration coefficient

A

a decrease in the surface area available for filtration

104
Q

what is plasma clearance

A

a measure of how efficiently the kidneys can clean the blood of a substance
= the volume of plasma completely cleared of a substance per minute (each substance has specific plasma clearance value)

105
Q

how do you calculate clearance of a subance

A

rate of excretion of X / plasma concentration of X

= [X]urine x Vurine / [X] plasma

106
Q

what substance does plasma clearance = GFR

A

inulin (rate of excretion matches rate of filtration)

107
Q

is inulin secreted or reabsorbed

A

no

108
Q

what can be used instead of inulin

A

creatinine

109
Q

what is the down side to creatinine

A

undergoes small amount of tubular secretion

110
Q

name a substance that is completely reabsorbed and not secreted

A

glucose

clearance= 0

111
Q

name a substance where clearance less than GFR

A

urea- as is partly reabsorbed and not secreted

112
Q

name a substance where clearance is more than GFR

A

H+ as is secreted but not reabsorbed

113
Q

what has happened when clearance

A

substance is reabsorbed

114
Q

what has happened when clearance = GFR

A

substance is neither reabsorbed or secreted

115
Q

what has happened when clearance > GFR

A

substance is secreted into tubule

116
Q

what can be used to calculate renal plasma flow

A

para-amino hippuric acid (is freely filtered at glomerulus and secreted into tubule- is not reabsorbed (completely cleared from plasma)

117
Q

what is a normal renal plasma flow

A

650 ml/min

118
Q

what should a GFR marker be

A

freely filtered

not secreted or reabsorbed

119
Q

what should a RPF marker be

A

filtered and completely secreted

120
Q

what is filtration fraction

A

the fraction of plasma flowing through the glomeruli that is filtered into the tubules

GFR/ renal plasma flow

Renal (27 decks)

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