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

B5.036 Renal Physiology I: Glomerular Filtration Flashcards

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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
podocytes
large cells that face the lumen of Bowman's space firmly attached to the basement membrane filtration slits between them
26
describe the portion of Bowmans capsule not in contact with the glomerular capillaries
flat cells resting on the basement membrane | eventually continues with the epithelium of the renal proximal tubule
27
what is a slit diaphragm?
located between podocyte foot processes zipper like structure constituted by numerous cross bridges major components: nephrin & p-cadherin
28
discuss the size of pores within the slit diaphragms between podocytes
40 x 140 A size of albumin nothing albumin or larger can fit through, thus proteins do not enter into the filtrate
29
properties of filtered molecules that enter into the ultrafiltrate
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
influence of size and charge on renal filterability
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
what molecule was used to demonstrate the influence of charge on filterability
dextrans exogenous polysaccharides of D-glucose that can be produced in various molecular weights and charges (neutral, cationic, and anionic)
32
what happens when the negative charge of the filtrating membrane is reduced?
can happen due to immunological or inflammatory damage | proteins can be filtered solely on size, can lead to proteinuria (lack of charge discrimination)
33
arterial blood flow path through the kidney
aorta > renal artery > interlobar arteries > arcuate arteries > interlobular arteries > afferent arteriole > efferent arteriole
34
where do arcuate arteries run
between cortex and medulla
35
venous blood flow path through the kidne
efferent arteriole > peritubular capillaries/ vasa recta > interlobular vein > arcuate vein > interlobar vein > renal vein
36
function of peritubular capillaries
provide nutrient to tubules and retrieve the fluid the tubules reabsorb
37
discuss the pressures of the renal circulation
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
normal renal blood flow
1.2 L/min | 20-25 % of cardiac output
39
normal renal plasma flow
660 mL/min
40
glomerular filtration rate (GFR)
125 mL/min | urine excreted = 1, 1.5 L/day
41
normal filtration fraction
GFR/RPF = 0.2
42
primary forces involved in ultrafiltration
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
what other factors contribute to ultrafiltration other than pressures?
surface area and permeability of the glomerular membrane | make up the ultrafiltration coefficient Kuf = 12
44
GFR=
Kuf * Puf
45
effect of afferent arteriole constriction on RBF and GFR
increases resistance to blood flow causes a fall in RBF fall in glomerular capillary pressure decreased GFR
46
effect of efferent arteriole constriction
increases resistance to blood flow rise in glomerular capillary pressure tends to increase GFR decreased RBF
47
autoregulation of RBF and GFR
tubuloglomerular feedback mechanism | myogenic response
48
extrinsic regulation of RBF and GFR
sympathetic nerves renin-angiotensin-aldosterone system humoral factors: angiotensin II, prostaglandins, NO, bradykinin, endothelin, adenosine
49
what is the autoregulatory range of renal blood flow
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
what is the myogenic response
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
what is the tubuloglomerular feedback mechanism
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
how do macula densa cells work in the TGF mechanism
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
adenosine
vasoconstrictor
54
NO
vasodilator
55
what are granular cells
part of the juxtaglomerular apparatus modified smooth muscle cells on the wall of the afferent arteriole responsible for secretion of renin
56
stimuli of renin-angiotensin system
1. increased sympathetic nerve activity 2. reduction of renal blood pressure 3. decreased Na+ delivery to macula densa
57
give an overview of the renin-angiotensin system
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
effect of aldosterone secretion
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
mechanism of action of angiotensin II on vessels
stimulates entry of Ca2+ into cell | Ca2+ increases actin-myosin coupling and stimulates vasoconstriction
60
mechanism of action of angiotensin II on adrenals
increases entry of Ca2+ into cell activates transcription factors and aldosterone synthesis increases aldosterone secretion from cell
61
why is important to determine the GFR
diagnosis of renal disease staging and progression of renal impairment adjusting the dosage of medications
62
measurement of glomerular filtration rate
``` 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
clearance
term used to describe the rate of removal or 'clearing' of a substance from the blood measures efficiency of kidney
64
normal GFR
125 ml/min | based on inulin rate of clearance
65
advantages of using creatinine to measure GFR
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
disadvantages of using creatinine to measure GFR
filtered and secreted can be overestimated overestimation and secretion can cancel each other out
67
GFR variance in the population
normal in young adults 100-125 decreases with age lower in females than males

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