Renal Physiology Flashcards
What does the glomerular filtration membrane consist of
Glomerular capillary endothelium
Basement membrane
Visceral layer of Bowmans capsule
Which layer of the glomerular filtration membrane is the limiting factor for filtration
Basement membrane
Which is the least filtrable through basement membrane
- 4 nm, -
- 4 nm , positive
- 7 nm, -
- 7 nm, positive
7 nm, negative
Similar to albumin
Net filtration formula in terms of hydrostatic and colloid pressure
And value
Pgc - pigc - Pbc+pibc
45-20-10+0
Equal to 15 mm Hg
Formula for GFR
GFR =Kf (net filtration pressure)
Kf Formula
Ultrafiltration constant
Permeability x surface area
What are the three ways in which increase sympathetic discharge causes decreased GFR
Mesangial cell contraction
Afferent arterial constriction
Increase renin from JG cells
From afferent to efferent arterioles Which of the following increases PGC PiGC PBC Net filtration pressure
PiGC
PBC is unchanged
Net filtration pressure is decreased
Renal bloodflow value
1100-1200 mL per minute
Renal plasma flow value
625-630 mL per minute
GFR value
125 mL per minute
Filtration fraction formula and value
GFR/RPF
=125/625
=0.20 (0.16-0.20)
Or 16–20%
What does freely filtered really mean
20 % is filtered in single circulation
By repeated circulation substance will be completely eliminated by blood
Increased GFR in
a) dilatationn of afferent
b) constriction of efferent
Both
But better answer is dilatation of afferent
Know why -.-
When does filtration fraction increase
a) afferent artery dilatation
b) efferent artery constriction
Efferent artery constriction better answer as FF=GFR/RPF
here GFR increases and RPF decreases
Therefore FF increases more
What is the dual effect on GFR by efferent artery constriction
Mild to mod constriction- increase GFR
Severe constriction-decrease GFR
Effect of angiotensin II on GFR
Angiotensin II (low conc) - increase GFR Eg.physiological,prolonged standing,renal artery stenosis
Angiotensin II (high conc) - decreases GFR Eg.haemorrhage,hypovolemia,dehydration
Which substances freely filtered,not reabsorbed,not secreted by kidney
Inulin
Which substances freely filtered,completely reabsorbed by kidney
Glucose
Amino acid
HCO3- (if normal)
Which substances freely filtered,partly reabsorbed by kidney
Urea
Electrolytes
Water
Which substances freely filtered , completely secreted by kidney
PAH (low concentration)
Which substances freely filtered,partly secreted by kidney
PAH
Creatinine
What is clearance
Clearance of substance is volume of plasma of that substance or free of substance in unit time
Clearance formula
UxV/pl
U-urinary concentration of X
V-rate of urine flow
Pl-plasma concentration of X
Clearance of what substance is used for estimation of GFR
Inulin (more accurate)
Creatinine (slightly increased)
A attacks E
E attacks A
Mnemonic means
Angiotensin II -efferent artery constriction
Epinephrine (sympathetic discharge)-afferent artery constriction
What is free water clearance
Rate of ruins flow - clearance of osmoles
What does it mean when free water clearance = 0
Solute free water in urine wrt solute free water in plasma is equal
What does it mean when free water clearance = positive
Urine is hypotonic wrt to plasma
What does it mean when free water clearance = negative
If urine is hypertonic wrt plasma
Marathon runner who sweats a lot
What is the free water clearance
Max swearing
Max antidiuresis
Therefore urine concentrated
Therefore answer negative
In diabetes insipidus what is the free water clearance
ADH absent in DI
Therefore urine dilute
Therefore positive
Tubular functions
Look at the diagram in your notes
Hormone present in glomerulus and what does it do
ANP
Mesangial cell relaxation
Increase in GFR
Hormones present in PCT and what do they do
Angiotensin II
Increase Na reabsorption
PTH - decreases phosphorus reabsorption
TAL hormones present and their functions
Angiotensin II
Increases Na reabsorption
DCT hormones present and their functions
PTH
Increase calcium reabsorption
What hormone releases when blood volume decreases
Aldosterone through RAAS
Increases in blood volume releases which hormone
ANP
What is free water clearance
Rate of ruins flow - clearance of osmoles
What does it mean when free water clearance = 0
Solute free water in urine wrt solute free water in plasma is equal
What does it mean when free water clearance = positive
Urine is hypotonic wrt to plasma
What does it mean when free water clearance = negative
If urine is hypertonic wrt plasma
Marathon runner who sweats a lot
What is the free water clearance
Max swearing
Max antidiuresis
Therefore urine concentrated
Therefore answer negative
In diabetes insipidus what is the free water clearance
ADH absent in DI
Therefore urine dilute
Therefore positive
Tubular functions
Look at the diagram in your notes
Hormone present in glomerulus and what does it do
ANP
Mesangial cell relaxation
Increase in GFR
Hormones present in PCT and what do they do
Angiotensin II
Increase Na reabsorption
PTH - decreases phosphorus reabsorption
TAL hormones present and their functions
Angiotensin II
Increases Na reabsorption
DCT hormones present and their functions
PTH
Increase calcium reabsorption
What hormone releases when blood volume decreases
Aldosterone through RAAS
Increases in blood volume releases which hormone
ANP
Filtered load formula
GFR x plasma conc
Which parts are Na reabsorbed in nephrons
Na reabsorbed in All parts of nephrons except in DTS
% of Na reabsorbed in each part of nephron
PCT - 60% DTS- nothing TAL- 30% DCT-7% Late DCT and CD -3% (regulated by aldosterone)
Transports in PCT for Na
Na-K ATPase
Na co-transport
Na counter transport
Know the diagram xD
(Notes)
What does PTH inhibit in PCT
Inhibits Na-Pi co-transport
Increase urinary loss of Pi
(Known as phosphaturic action of PTH
TAL which transport helps in Na reabsorption
Na-K-2Cl co transport
Na-K ATPase
LASIX (loop diuretic) acts on which part
Na-K-Cl co-transport channel inhibition in TAL
What are the substances with Na co-transported in PCT
Glucose
Amino acid
Pi
Co-transport for reabsorption of Na in DCT
Na-K ATPase
Na-Cl co-transport
Thiazides act on which part of nephron
Na-Cl co-transport in DCT
Cells present in late DCT and CD responsible for reabsorption and secretion
P cells (principal) I cell (intercalated)
What do P cells do (late DCT and CD)
Na reabsorption
K secretion
H2O reabsorption
What do I cells do (late PCT and CD)
H secretion
Remember ACID and I cells have ‘I’
Channels present on p cells (late DCT and CD)
Na-K ATPase channel
ENaC ( epithelial Na channel)
(Aldosterone stimulates both)
Where is K reabsorbed in nephron and how
PCT and TAL
PCT- passive (solvent drag-leaky tight junctions) and active (pump?)
TAL-Na-K-2Cl co-transport
Where is K secreted in nephron
Late DCT and CD (passive)
Aldosterone
Sites of mechanism of Ca reabsorption
Similar to Na
Maximum Ca reabsorption where (nephron)
PCT
What happened to Ca in DCT
Increased Ca reabsorption due to PTH
% of Ca reabsorbed and secreted
99% filtered
1% excreted
Maximum Mg reabsorption in nephron
TAL
Renal handling of glucose site
PCT
Channels on PCT for glucose reabsorption
Na-K-ATPase
Early PCT-SGLT-2 (co-transport) and GLUT-2
Late PCT-SGLT-1 and GLUT-1
Renal threshold means
Plasma concentration beyond which glucose begins to appear in the urine (180-200 mg/dl)
If PAH concentration is high what happens to the clearance and renal blood flow
Clearance is falsely low therefore RBF is also falsely low
Amount of water reabsorbed in different parts of nephron
(GFR=180L/day)
PCT- 2/3rd (obligatory reabsorption of H2O)
DTS-15-20%
CD-13-15% (facultative reabsorption of H2O)
What is transport maximum of glucose
Maximum rate of glucose reabsorption
Male 375 mg/min
Female 300 mg/min
Where is aquaporin 1,2,3,4 present
Ap1
Ap2-luminal membrane
Ap3 and Ap4- basolateral membrane
Maximum H secretion occurs in
PCT
Acidification of urea occurs in
CD
Channels involved in secretion of H in PCT
HCO3-Cl (basolateral membrane)
Na-H (luminal membrane)
Know diagram -.-
Of everything
What is the pH of tubular fluid after end of PCT
7.3 (same,no acidification present in PCT)
Carbonic anhydrase inhibitor increases what
Na
HCO3-
H2O
Where is the filtered HCO3 reabsorbed
PCT (80%)
TAL
DCT (both together 20%)
Acidification of urine is due to which acid
Phosphoric acid
What are the urinary buffers
HCO3 (most important urinary buffer)
Phosphate buffer
Ammonia buffer
Most important urinary buffer in DCT and CD
Phosphate (in physiological conditions)
Most important urinary buffer in acidosis
Ammonia> phosphate
Ammonia is an inducible buffer
(NH3 production increases)
Factors affecting H+ secretion
Increase pCO2
Aldosterone
CA inhibitor
Hyperaldosteronism can never cause
a) acidosis
b) alkalosis
Acidosis
Regulation of Na excretion of GFR
Myotonic mechanism of autoregulation
Tubuloglomerulat feedback
Glomerulotubular balance
Know them in detail
Parts of juxtaglomerular apparatus
JG cells
Macula densa
Lacis cells
Know where they are and their function
What substance causes vasoconstriction of afferent arteriolar in tubuloglomerulat feedback
Adenosine
What substance causes vasodilation of afferent arteriolar in tubuloglomerular feedback
Nitric oxide
Counter current multiplier and its function
Loop of henle
Creates medullary interstitial hyperosmolality
Counter current exchanger and its function
Vasa recta
Maintains the medullary interstitial hyperosmolality
What is the maximum urinary osmolality
1200 most/L
What are the requirements for concentration of urine
ADH- insertion of Ap-2 on luminal membrane of P cells
Hyperosmolal medullary interstitium
Know the mechanisms pls
What is the range of urine osmolality
Usual-
300-1200 mosm/L
Possible
50-1200 mosm/L
What are the solutes responsible for medullary interstitial hyperosmolality
Na K Cl (From TAL) Urea from medullary CD
What is urea cycling
Pls check diagram in notes
What is the advantage of urea cycling
Increase medullary interstitial osmolality
Parts of nephron permeable to urea
PCT
DTS
Medullary CD
Parts of nephron impermeable to urea
TAL
DCT
Cortical CD
What is the role of vasa recta
Only supply of blood 🩸 therefore oxygen to medulla
2 limbs of VR are counter current with each other and with LOH
Both limbs of VR freely permeable to solute and water
VR receive <5% of RBF,therefore slow rate of blood flow in VR (helps in exchange)
