Renal Regulation of water & acid-base balance Flashcards
What is Osmotic pressure dependent on?
number of solute particles
How do you work out Osmolarity?
Concentration X number of dissociated particles.
e.g osmolarity of 100 mmol/L NaCl = 200 mOsm/L
What percentage of body weight is body fluid volume?
60%
How is body fluid volume split between intracellular and extracellular fluid?
2/3 Extracellular
1/3 Intracellular
What percentage of Intracellular fluid is Intravascular?
25%
Where is most extravascular bodily fluid found?
95% Interstitial Fluid
5% Transcellular Fluid
Give examples of Regulated & Unregulated water loss
Regulated - Renal regulation (urine production)
Unregulated - Sweat, Faeces, Vomit, Water evaporation from respiratory lining and skin.
Outline Positive water balance
1 - High water intake
2 - Increased ECF volume, decreased osmolarity and [Na+ ]
3 - Hypoosmotic urine production
4 - Osmolarity normalises
Outline Negative water balance
1 - Low water intake
2 - Decreased ECF volume, increased osmolarity and [Na+]
3 - Hyperosmotic urine production
4 - Osmolarity normalises
What percentage of water is reabsorbed in the proximal convoluted tubule?
67%
What cannot be absorbed in the thin ascending limb of the loop of Henle?
Water
What is passively absorbed in the thin ascending limb of the loop of Henle?
NaCl
What is actively absorbed in the thick ascending limb of the loop of Henle?
NaCl
What is passively absorbed in the descending loop of Henle?
Water
15%
What cannot be absorbed in the descending loop of Henle?
NaCl
What allows the passive absorbtion of water in the descending loop of Henle and collecting duct?
A hyperosmotic medullary interstitium and a gradient across the medulla.
What process creates a gradient in the medullary interstitium?
Countercurrent multiplication
Describe Countercurrent multiplication?
Active salt reabsorption from the ascending loop of Henle into the medullary interstitium increases osmolarity in the descending loop of Henle, leading to passive water reabsorption across the gradient.
Describe Urea Recycling?
Urea is transported into the medullary instertitium via UT-A1&3 in the collecting duct and then enters the descending loop of Henle via UT-A2, thus increasing the instertitium osmolarity and increased water reabsorption.
Urea Concentration occurs and urea excretion requires less water.
What is the role of Vasopressin in Urea Recycling?
Boosts UT-A1 &UT-A3 numbers.