L03a: Body Fluids Flashcards
What are the 4 ways out excreting water
Lungs
Skin
Urine
Faeces
What are the compartments of water
Plasma water Intracellular Interstitial Transcellular Fat
What site is the extracellular fluid found
Plasma water
Intersitial
Fat
How does water move from the plasma water
1) ingested into the plasma
2) passes to intersitial space
3) can cross to intracellular compartment
4) then to transcellular if possible
Where is most of the water found
Intracellular compartment
What is the total body fluid of an average 70kg person
42 litres
List the largest to smallest water depending on its compoartmwern
Intracellular
Interstitial
Plasma
Transcellular
What are the examples of transcellular compartments
Peritoneal space
CSF
Pleural cavity
Synovial fluid
How to we measure body fluid
Volume of distribution
How do we carry out volume of distribution
Inject a known amount of drug
Then measure its concentration in plasma
What is the volume of distribution equation
VD= known amount injected/ concentration in plasma
What happens to the volume of distribution if the concentration of a drug is higher outside the plasma
Volume of distribution is higher
How to we measure total body water
We used labelled water Inject a volume volume Allow it to equilibrate Take a blood sample Measure normal water to labelled water ratio
What does blood contain
Plasma: the fluid component of blood
Haematocrit: cells in the blood
What are substances are in body fluids
Sodium Potassium Calcium Chloride Bicarbonate Glucose
Which ion is the highest intracellular
Potassium
Which ion is the highest extracellular
Sodium
Chloride
What happens to half of the calcium when it is the circulation
Binds to albumin
How do we measure the free calcium (the half of the calcium not bound to albumin)
Calculate a corrected calcium concentration
What is an osmole
The number of molecules that a compound dissociated into when in dissolved solution
What is unit of osmole represented as
Osm or osmol
If there is 100 millimol of sodium chloride what would its miliosmole be in solution
200 mOsm
Why is the mili osmole of sodium chloride not 100 but 200
Because sodium chloride which is one molecule dissociates into 2 molecules of na+ and cl- so there is 200 mOsm of sodium chloride in solution
What is the mili osmole of 4 mmol of glucose in solution
4mosm because glucose does not dissociate in solution
What is the definition of osmolality
The number of osmoles per unit mass of solvent
What is the unit of osmolality
Osm per kg
What is osmolarity
The number of osmoles per unit volume of solution
What is the unit of osmolarity
Osm per litre
What is osmotic pressure
The pressure that occurs between 2 solutions with different molecules = osmotic pressure
What happens to water when there is a compartment with high solutes
Water moves to that compartment by osmotic pressure
What does it mean if 2 solutions are isosmotic
They share the same osmolality
What does it mean if a solution is isotonic
There will not be a net fluid movement usually in RBC
What is oncotic pressure
The pressure generated by proteins that draws water
What is the hydrostatic pressure
The pressure generated by the heart
What does osmotic pressure cause
Draws water towards it
What is the emergency treatment for intracrainal haemorrhage
Inject mannitol
How does mannitol draw water from the intracellular and transcellular space to reduce intracrainal pressure
Mannitol in the plasma increases osmolality and osmotic pressure
Water is drawn into the plasma from the intracellular and transcellular space
