Intro to Renal Flashcards
1
Q
regulatory functions of the kidney
A
- extracellular fluid volume
- extracellular fluid osmolarity
- extracellular fluid ion composition
- clearance of metabolic end products, toxins and drugs
- endocrine- erythropoietin, active vitamin D, renin
2
Q
body fluid compartments
A
- total body fluid decreases with age from approx 75% of BW to 50%
- ECF contracts from 50% of BW to 33% in adults
- TBW is inversely proportional to % body fat and TBW decreases as a % of BW with an increased % of body fat- puberty increases body fat in women and decreases TBW
- solute comp of ICF/ECF different, osm is the same
3
Q
body fluid balance
A
- kidneys monitor and maintain plasma volume and osm
- in turn maintains total body water and osm due to water and solute exchange between the ECF and ICF compartments
- kidneys are only effector organs of regulated water and salt excretion
- unregulated water and salt loss from TBW occurs in sweat, feces, insensible skin and lung loss
- kidneys are the effector organ compensating for the effects of variable consumption of solutes and water on ECF volume and osm by increasing or decreasing the excretion of solutes and water in the urine
4
Q
fluid and solute distribution between plasma and ISF
A
- fluid distribution between plasma and ISF is driven by the balance between hydrostatic pressure and osmotic pressure differences across the cap wall
- filtration out of intravascular compartment into the extravascular compartment (ISF) and reabsorption is driven by opposing forces
- rate =lp [(Pc-Pi)-(piC-piI)], lp is hydraulic conductivity coefficient
P is hydrostatic, pi is oncotic
-filtration driving is hydrostatic, absorption is driven by oncotic pressure
5
Q
solute distribution
A
- solute concentration is similar between ISF and plasma with the exception of negatively charged plasma proteins
- impermeable to cap wall and remain in intravascular compartment
- therefore, osmotic pressure is higher in plasma than ISF (osm higher)
6
Q
edema
A
- excess accumulation of fluid in the interstitial space due to cardiac, renal, hepatic, or endocrine dysfunction
- localized or generalized imbalance of hydrostatic and osmotic pressure across the cap wall induces a fluid shit from the intra to extravascular space
- CHF, nephrotic syndrome, liver disease can cause an isotonic retention of sodium and water as well as decreased circulating volume, which may decrease renal perfusion pressure and activate the R-A-A system, further increasing the sodium retention and maintaining edema
- an increase or decrease in edema can be assessed clinically by the patients weight
7
Q
fluid and solute distribution between ICF and ECF
A
- net movement of water between ICF and ECF is driven only by osmotic pressure differences across the cell membrane
- permeating and non permeating solute concentrations in ICF and ECF determine water movement
- water moves passively across the cell membrane down its concentration gradient
- water follows solute
8
Q
isosmotic fluid expansion
A
- IV isosmotic fluid gain to ECF
- increase ECF vol
- ECF osm stays
- no DF
- no change in ICF vol/ osm
- dilution of plasma proteins and decrease Hct
9
Q
isosmotic volume contraction
A
- diarrhea, isosmotic fluid loss
- decrease in ECF vol
- no change in ECF osm
- no DF, no change in ICF vol/ osm
- concentration of protein and increased Hct
10
Q
hyperosmotic volume contraction
A
- profuse sweating and/or water deprivation
- decrease in ECF vol and increase in ECF osm
- water moves from ICF to ECF
- decrease ICF vol and inc ICF osm
11
Q
hyperosmotic volume expansion
A
- high NaCl intake without fluids, gain of solute
- increase ECF osm
- water moves to ECF
- decrease ICF vol and increase ICF osm
- increase ECF vol
- ICF Na concentration remains unchanged due to Na-K pump activity balancing Na entry
12
Q
hypoosmotic volume expansion
A
- syndrome of inapproprate ADH (gain of water)
- excess water reabsorption from collecting ducts into ECF causes:
- increased ECF vol and decreased osm
- water moves to ICF
- inc ICF vol and dec ICF osm
13
Q
hypoosmotic volume contraction
A
- aldosterone insufficiency and decreased renal NaCl reabsorption (loss of solute in excess of water)
- dec in ECF osm
- water moves to ICF
- increase ICF vol and dec osm
- decrease ECF vol
14
Q
solute distribution 2
A
- ECF and ICF different due to Na/K pumo
- exchanges intracellular Na and extracellular K
- K high inside and Na low
- K low outside and Na high
- sum is same so osm is still 300
15
Q
cells shrinking
A
- if cells shrink in response to an increase in ECF osm (water to ECF)
- cells activate solute uptake mechanisms to inc ECF osm
- drives water back into cells to restore volume to normal
- regulatory volume increase
