Body fluids Flashcards
What is the average input of fluid a day and by what mechanisms?
2.5L/day - drinking, eating, metabolism of carbohydrates
What is the average urinary output a day?
1.5L/day but may vary depending on regulation
What happens to the remaining volume of water?
0.9L is lost through lungs, skin and faeces - exercise, metabolism, temp, disease
How much fluid is in the intracellular compartment?
28L (inside of cells)
How much fluid is in the extracellular compartment?
14L
Which areas contribute to the extracellular compartment?
Interstitial and plasma
What is transcellular fluid?
Fluid that must cross an epithelial barrier such as CSF, plural, periotneal, synovial
How much water is a 70kg person?
42L
What is the equilibrium of a substance depend on when moving through compartments?
Permeability
pH of the compartment
Binding capacity
Fat solubility
What is the volume of distribution?
Vd = Q / Cp
Q = total amount of substance
Cp = Concentration of substance in plasma
It is the volume of fluid needed to contain the administered substance at the same concentration as in the plasma.
How can the plasma be measured?
Use a substance that binds strongly to plasma proteins - heparin, insulin, Evan’s blue
How is extracellular fluid measured?
Use a strong polar molecule as it can’t cross the membrane
How can fat or water be measured?
Ethanol or radioactive H for water
What is the concentration of Na both intracellular and extracellular?
Intra - 15mM
Extra - 140mM
What is the concentration of K both intracellular and extracellular?
Intra - 140mM
Extra - 4mM
What is the concentration of Ca extracellular?
2.4mM as half being bound and half free
What is the concentration of Cl both intracellular and extracellular?
Intra - 4mM
Extra - 110mM