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GIR Test 2 > B5.036 Renal Physiology I: Glomerular Filtration > Flashcards

B5.036 Renal Physiology I: Glomerular Filtration Flashcards

1
Q

homeostatic functions of the kidneys

A

regulation of extracellular fluid volume
regulation of extracellular fluid electrolyte composition
regulation of extracellular fluid acid base balance

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2
Q

excretory functions of the kidneys

A

metabolic waste products

foreign substances and toxins

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3
Q

endocrine functions of the kidneys

A

regulation of BP
erythropoiesis
calcium metabolism

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4
Q

vertebral level of kidneys

A

T-12 to L3

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5
Q

discuss the structure of the kidney

A

renal artery and vein, nerves, and renal pelvis enter and exit the organ at the hilum
outer zone = cortex
inner portion = medulla
medulla contains 8-18 pyramids (base directed at cortex)
between pyramids are projections called renal columns
apex of pyramid = papilla
each papilla > minor calix > major calix > renal pelvis > ureter

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6
Q

how many nephrons in a kidney

A

1 million

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7
Q

2 types of nephrons

A

cortical- whole structure in renal cortex

juxtamedullary - part of tubular region extends into medulla

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8
Q

what is the renal corpuscle and what is its function?

A

formed by glomerulus surrounding by Bowman’s capsule

filtering component of the nephron located in the cortex

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9
Q

describe the structure of the glomerulus

A

afferent and efferent arterioles

mesangial cells between capillary loops

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10
Q

functions of mesangial cells

A

supporting structures
contractile properties
phagocytic activities
secrete substances can locally regulate glomerular function

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11
Q

describe the structure of Bowman’s space

A

vascular layer and parietal layer

bowman’s space between layers- receives renal filtrate

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12
Q

what is the ultrafiltrate made up of

A

plasma without proteins

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13
Q

structure of the renal tubule

A 
3 sections
proximal tubule
loop of henle
distal convoluted tubule
convert blood filtrate to urine
reabsorb water and some solutes back into blood
secrete some solutes into tubular lumen
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14
Q

what is the juxtaglomerular apparatus

A

interaction between distal tubule and vascular pole of renal corpuscle
tubular epithelial cells + extraglomerular mesangial cells + wall of afferent arteriole

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15
Q

basic functions of the nephron

A
  1. filtration
  2. reabsorption
  3. secretion
  4. excretion
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16
Q

substance handled by the kidneys only in filtration

A

inulin

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17
Q

substances that are primarily reabsorbed

A

AAs
glucose
Na+
Cl-

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18
Q

substances that are primarily secreted

A 
metabolic products and drugs
ex: 
penicillin
furosemide
hippurates
morphine
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19
Q

substances that can be reabsorbed or secreted depending on the segment

A

K+

urate

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20
Q

why is the kidney said to be a polarized organ

A

blood and urine kept very separate

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21
Q

3 factors involved in renal filtration

A
  1. properties of the glomerular filtration membrane
  2. properties of the filtered molecules
  3. forces involved in filtration
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22
Q

capillary endothelium

A

single cell layer that has numerous pores or fenestrae

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23
Q

basement membrane

A

non cellular mesh of negatively charged glycoproteins and proteoglycans

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24
Q

filtration pathway in the renal corpuscle

A

capillary endothelium
basement membrane
podocytes
more selective in each layer

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25
Q

podocytes

A

large cells that face the lumen of Bowman’s space
firmly attached to the basement membrane
filtration slits between them

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26
Q

describe the portion of Bowmans capsule not in contact with the glomerular capillaries

A

flat cells resting on the basement membrane

eventually continues with the epithelium of the renal proximal tubule

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27
Q

what is a slit diaphragm?

A

located between podocyte foot processes
zipper like structure constituted by numerous cross bridges
major components: nephrin & p-cadherin

28
Q

discuss the size of pores within the slit diaphragms between podocytes

A

40 x 140 A
size of albumin
nothing albumin or larger can fit through, thus proteins do not enter into the filtrate

29
Q

properties of filtered molecules that enter into the ultrafiltrate

A

ions and small molecules up to 2 nm (7000 Da)
above 3 nm have increasing difficulty filtering
nothing larger than 4 nm can pass
cationic molecules favored over anionic

30
Q

influence of size and charge on renal filterability

A

cationic molecules with a radius between 2-4 nm filter in a greater extent than anionic molecules of the same size
due to electrostatic interactions with negatively charged glycoproteins on BM

31
Q

what molecule was used to demonstrate the influence of charge on filterability

A

dextrans
exogenous polysaccharides of D-glucose that can be produced in various molecular weights and charges (neutral, cationic, and anionic)

32
Q

what happens when the negative charge of the filtrating membrane is reduced?

A

can happen due to immunological or inflammatory damage

proteins can be filtered solely on size, can lead to proteinuria (lack of charge discrimination)

33
Q

arterial blood flow path through the kidney

A

aorta > renal artery > interlobar arteries > arcuate arteries > interlobular arteries > afferent arteriole > efferent arteriole

34
Q

where do arcuate arteries run

A

between cortex and medulla

35
Q

venous blood flow path through the kidne

A

efferent arteriole > peritubular capillaries/ vasa recta > interlobular vein > arcuate vein > interlobar vein > renal vein

36
Q

function of peritubular capillaries

A

provide nutrient to tubules and retrieve the fluid the tubules reabsorb

37
Q

discuss the pressures of the renal circulation

A

afferent and efferent arterioles are the major resistance sites and thus the major sites for control of flow
hydrostatic pressure > oncotic pressure = filtration in glomerular capillaries
oncotic pressure > hydrostatic pressure = absorption in peritubular capillaries

38
Q

normal renal blood flow

A

1.2 L/min

20-25 % of cardiac output

39
Q

normal renal plasma flow

A

660 mL/min

40
Q

glomerular filtration rate (GFR)

A

125 mL/min

urine excreted = 1, 1.5 L/day

41
Q

normal filtration fraction

A

GFR/RPF = 0.2

42
Q

primary forces involved in ultrafiltration

A

major force causing filtration = hydrostatic pressure in glomerular capillary bed, 60 mmHg
opposed by smaller hydrostatic pressure within the tubule = 20 mmHg
opposed by colloid osmotic pressure of the blood = 30 mmHg
NET = 60-20-30 = 10 mmHg

43
Q

what other factors contribute to ultrafiltration other than pressures?

A

surface area and permeability of the glomerular membrane

make up the ultrafiltration coefficient Kuf = 12

44
Q

GFR=

A

Kuf * Puf

45
Q

effect of afferent arteriole constriction on RBF and GFR

A

increases resistance to blood flow
causes a fall in RBF
fall in glomerular capillary pressure
decreased GFR

46
Q

effect of efferent arteriole constriction

A

increases resistance to blood flow
rise in glomerular capillary pressure tends to increase GFR
decreased RBF

47
Q

autoregulation of RBF and GFR

A

tubuloglomerular feedback mechanism

myogenic response

48
Q

extrinsic regulation of RBF and GFR

A

sympathetic nerves
renin-angiotensin-aldosterone system
humoral factors: angiotensin II, prostaglandins, NO, bradykinin, endothelin, adenosine

49
Q

what is the autoregulatory range of renal blood flow

A

90-180 mmHg
RBF and Pgc do not change significantly when arterial pressure changes within a wide range of values
RBF is fairly independent of renal perfusion pressure

50
Q

what is the myogenic response

A

automatic adjustment of afferent arteriole
for example: when the arterial pressure increases, walls of afferent arteriole are stretched, triggering the contraction of the vascular smooth muscle
subsequent increase in resistance counteracts the increment in RBF and both RBF and GFR remain unaltered

51
Q

what is the tubuloglomerular feedback mechanism

A

RBF and GFR regulated by changes in tubular flow rate and fluid composition
TGF mechanism mediated by cells of macula densa
when an increase in GFR increases fluid flow and NaCl concentration, there is a contraction of the afferent arteriole which returns RBF and GFR to normal levels

52
Q

how do macula densa cells work in the TGF mechanism

A

able to sense changes in NaCl concentration through NA+K+2Cl- transporters present on their membrane
release messengers that target smooth muscle cells to contract afferent arteriole

53
Q

adenosine

A

vasoconstrictor

54
Q

NO

A

vasodilator

55
Q

what are granular cells

A

part of the juxtaglomerular apparatus
modified smooth muscle cells on the wall of the afferent arteriole
responsible for secretion of renin

56
Q

stimuli of renin-angiotensin system

A
  1. increased sympathetic nerve activity
  2. reduction of renal blood pressure
  3. decreased Na+ delivery to macula densa
57
Q

give an overview of the renin-angiotensin system

A

renin converts angiotensinogen to angiotensin I
ACE converts angiotensin I to angiotensin II
angiotensin II stimulates arteriolar vasoconstriction, sodium reabsorption in the proximal tubules, and activation of aldosterone secretion

58
Q

effect of aldosterone secretion

A

increases Na+ reabsorption by the ascending loop of Henle, the distal tubules, and the collecting ducts
increases K+ secretion
increases blood volume and pressure

59
Q

mechanism of action of angiotensin II on vessels

A

stimulates entry of Ca2+ into cell

Ca2+ increases actin-myosin coupling and stimulates vasoconstriction

60
Q

mechanism of action of angiotensin II on adrenals

A

increases entry of Ca2+ into cell
activates transcription factors and aldosterone synthesis
increases aldosterone secretion from cell

61
Q

why is important to determine the GFR

A

diagnosis of renal disease
staging and progression of renal impairment
adjusting the dosage of medications

62
Q

measurement of glomerular filtration rate

A 
GFR = Ux * V / Px
excretion rate / plasma concentration
Ux = urine concentration of substance x
V = volume of urine per minute
Px = plasma concentration of substance x
63
Q

clearance

A

term used to describe the rate of removal or ‘clearing’ of a substance from the blood
measures efficiency of kidney

64
Q

normal GFR

A

125 ml/min

based on inulin rate of clearance

65
Q

advantages of using creatinine to measure GFR

A

end product of protein metabolism
always present in blood at relatively constant concentration
freely filtered and secreted by the proximal tubule
no need for IV infusion
clearance time over long period
no emptying of bladder needed

66
Q

disadvantages of using creatinine to measure GFR

A

filtered and secreted
can be overestimated
overestimation and secretion can cancel each other out

67
Q

GFR variance in the population

A

normal in young adults 100-125
decreases with age
lower in females than males

GIR Test 2 (20 decks)

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