Fluid and Electrolyte Balance Flashcards
What is the total length of glomeruli in the kidney?
1.5m
What happens to body fluid when the kidneys stop working?
Fluid begins to accumulate
- pulmonary oedema
- interstitial oedema
What electrolyte is increase when kidneys stop working?
Potassium
= hyperkalaemia
ECG
- arrhythmia
- asystole (flat line)
What’s the main ion inside cells?
K+
What’s the main ion ECF
Na+
Which compartment contains most fluid?
IC 60%
How much CO do the kidneys receive?
20%
What is the response of SNS on the kidney?
decrease plasma volume
SNS vasoconstricts the afferent arterioles to restrict blood flow
What is the response of Ang II on the kidney?
decrease BP
Ang II vasoconstricts efferent arterole to maintain eGFR
What is the response of prostaglandins on the kidney?
Dilate afferent arteriole
What charge is the glomerular BM?
Negatively
How much of the filtrate is reabsorbed?
99%
180L/day
What’s the average amount of urine produced per day?
approx. 1.8L
What’s the unit of measure of concentration of a solute?
Osmole
is osmolality temperature-dependent?
No its temperature-independent
What’s the concentration of solutes in plasma?
285-295mOsm/kg
approx. 300mOsm/kg
Where does majority of reabsorption take place?
70% PCT
On the luminal side what is the main exchangers for reabsorption
Mainly
- Na-X co-transporters
- Na+/H+ exchanger
What is the driver of absorption?
Basolateral 3Na+/2K+-ATPase
- creates concentration gradient for Na+
How long is the PCT?
14mm
Which part of the nephron concentrates urine?
LOH and CD
What system does the LOH use?
Countercurrent multiplier system
Which part of the nephron is impermeable to H2O?
TALH
What main channel is found on TALH? And what drug can be used to inhibit this?
NKCC
Loop diuretic
What’s the main function of TALH?
Increases interstitium concentration
Providing a concentration gradient to promote H2O rebasorption from thin DLH
How does the vasa recta work to maintain gradient?
It doesn’t wash away the gradient by using countercurrent exchange
What is the main channel on DCT?
NCC
Na/Cl co-transporter
What drug acts on DCT and on what channel?
Thiazide
NCC
How long is the DCT?
1mm
By the time the filtrate reaches the CD how much of the filtrate is left? And why?
5%
PCT -70%
LOH -20%
DCT -5%
= 5% left
What acts on the CD to decrease volume loss?
- ADH (posterior pituitary gland)
- binds to V2R
- inserts AQs - Aldosterone
- causes translocation of ENaC into cortical CD
- promotes Na+ reabsorption and K+ loss
What diuretics can be used on the CD
K+-sparing
- MR-antagonist: spironolactone
- ENaC blockers: amiloride
Where is aquaporin I and II inserted?
I - TDLH
II - CD
What are the main channels on PCT?
Basolateral: 3Na+/2K+-ATPase
Luminal: Na+/H+ antiporter
What are the main channels on TDLH?
AQ I
What are the main channels on TALH?
NKCC
-inhibited by loop diuretics e.g. flurosemide and bumetinde
What are the main channels on CCD?
AQ II (ADH)
ENaC (aldosterone)
What is the hereditary disorder that effects the PCT?
Fanconi’s syndrome
What is the hereditary disorder that effects the NKCC2?
Bartter’s syndrome
What is the hereditary disorder that effects the NCC?
Gitelman’s syndrome
What is the hereditary disorder that effects the eNaC
Liddle’s
What are the main waste products measured?
Creatinine and urea
What is Hemolytic-uremic syndrome?
Hemolytic-uremic syndrome is a disease characterized by a triad of
- hemolytic anemia (anemia caused by destruction of red blood cells)
- acute kidney failure (uremia)
- low platelet count (thrombocytopenia).
How is urea formed?
byproduct of AA metabolism in the liver
What’s the importance of urea in kidney function?
Urea trapping
- reabsorbed in the inner medullary CD
- involved in countercurrent exchange and maintaining concentration gradient for H2O reabsorption
What is creatinine made from?
Breakdown product of creatinine phosphate
- muscle metabolism
What’s the importance of creatinine in kidney function?
Freely filtered
NOT re-absorbed
- can be used as a reliable marker of kidney function
What is the range of urine concentration?
200-1400mOsm/kg
What is the minimum urine osmolality?
50mOsm/kg
What is the minimum urine output?
0.4L/day
What is the maximum urine output?
12L/day
What is the concentration of waste products excreted/day
600mOsmol
What’s the volume of glomerular filtrate generated from plasma per min and how much if reabsorbed?
100mL/min
99% reabsorbed - 70% PCT
