In a typical male who has a total body water of 42L, how much intracellular fluid is there?
In a typical male who has a total body water of 42L, how much extracellular fluid is there?
In a typical male who has a total body water of 42L, how much interstitial fluid is there?
Proteins and Calcium
Much less in interstitial fluid
Most calcium is protein bound - if there is less protein, there is less calcium
Concentrations between plasma and interstitial fluids are similar apart from 2. What are the two solutes that differ? ...How do they differ? ...Why is this?
-Known quantity of a marker substance known to be restricted to a particular compartment is injected
-Allowed to distribute
How are body fluid volumes measured?
(Amount given - Amount lost) / Concentration through body
What is the calculation for volume using dilution methods?
What compounds are used in dilution techniques to calculate extracellular fluid volume? (2)
Isotopically labelled plasma proteins
What compounds are used in dilution techniques to calculate plasma volume?
Must be excluded from all cells but free to distribute throughout extracellular space
What is the requirement of a compound being used to measure extracellular fluid volume?
Must remain within the vascular system
What is the requirement of a compound being used to measure plasma volume?
How much osmotic pressure does 1 gram of a non dissociating substance dissolved in 1 kg of water exert?
THe sum of the osmolalities due to each of the constituents in a solution
What is the total osmolality for a solution?
The influence os its osmolality on the volume of cells
What does the tonicity of a solution refer to?
Iso-osmotic and Isotonic
Because cell volume remains stable - implying two fluid have same osmolality
What are two solutions with same osmolality described as? ...Why?
(hydrostatic pressure of capillary - hydrostatic pressure of interstitum)
(oncotic pressure of capillary - oncotic pressure of interstitium
(hydrostatic pressure of interstitial - hydrostatic pressure of capillary)
(oncotic pressure of interstitial - oncotic pressure of capillary)
What is the formula for net filtration pressures from a capillary to interstitial fluid? ...How would this formula be different if net reabsorption was being calculated?
On average how many litres of fluid move from capillaries into interstitial fluids a day? ...How many are reabsorbed?
-Reduced hydrostatic pressure in capillary due to blood loss causes less fluid to be filtered
-Reduced plasma increases the concentration of proteins in the plasma - causes increased oncotic pressure, which causes increased absorption
Why does haemorrhage lead to increase fluid reabsorption from interstitial fluids into plasma?
-Increased hydrostatic pressure in capillary causes more fluid to be filtered out of the kidney and less to be reabsorbed
-Causes accumulation of fluid in the tissues
How does ingestive heart failure lead to oedema?
-Reduced concentration of proteins in plasma causes decreased oncotic pressure
-So more plasma filtered out into tissues, less reabsorption
-Leads to accumulation of fluid in tissues
How does liver failure cause odema?
Drains into lymphatics
What happens to the excess fluid filtered into the interstitial fluid (and not reabsorbed into capillaries)?