Body Fluid Compartments; osmolality Flashcards
Body fat content varies inversely with what?
Water content
*this is why females have less water content than males*
What percent of water is interstitial fluid?
What percent of our boddy water is intracellular?
interstitial fluid = 15% body weight
intracellular fluid = 40% body weight
How much fluid makes up our Total Body fluid?
42 Liters - makes up 60% body weight overall
What do extra and intracellular fluids contain?
mainly water and electrolytes -as well as small quantities of non-electrolytes like amino acids, glucose etc.
In the extra cellular fluid, what ion is mainly present?
Na+ is the main positively charged ion
Cl - is the mian negatively charged ion
There is very little K+ in the ECF
What is the main ion present in the Intracellular fluid?
K+ is the main positively charged ion in the ICF
PO4- and proteins are the main negatively charged ion s
The process of maintaining the extracellular fluid through control mechanisms in the body is called…?
homeostasis
Describe one mechanism of ECF homeostastic control in the body related to glucose
After a meal when the glucose conc. is increased- body releases insulin to remove the glucose from the ECF - thus maintaining the body homeostasis
Big picture, are the ECF and ICF contents similar in ionic strength? Or do they vary?
They are near equal - there is only a slight difference that allows for action potentials
Does water freely move across cell membranes?
Yes - osmosis
What determines whether osmosis will occur or not?
there must be a difference in water concentrations
Describe what high osmotic pressure means
The higher the osmotic pressure of a solution, the lower the water concentration and the higher the solute concentration in the solution
The osmotic pressure exerted by particles in a solution is determined by ….?
the number of the particles per unit volume of fluid … not by the mass of the particles themselves
What is an osmole?
osmole refers to the number of osmotically active particles in a solution rather than molar concentration.
so a solution of 1 mole of glucose/liter has an osmolar concetnration of
1 osmole/L
What is the difference between osmolarity and osmolality?
osmolarity - used when the osmotically effective concentration of a solution is expressed in osmoles/Liter solution
osmolality - used when the osmotically effective concentration of a solution is expressed in osmoles/Kg solvent
*for dilute solutions like body fluids, osmolarity equals osmolality
Diabetes insipidus is characterised by what?
deficiency in Vasopressin (antidiuretic hormone) which would normally reduce urinary output and conserve water in the body
With diabetes insipidus, patients can produce up to 20L of very dilute urine daily
Why is it dangerous to be dehydrated or underhydrated?
Water can leave the cells by osmosis through the membranes thus increasing the osmolarity of the intercellular fluid and disrupting cellular function
mild cases = dry skin/tongue/sunken eyeballs
moderate cases = mental confusion/irrationality
sever = delirium, convulsions, coma
Why is water retention/overhydration possibly dangerous?
any free surplus H2O is promptly excreted so overhydration generally does not occur. In patients with renal failure, they cannot excrete dilute urine and they thus become hypotonic upon consuming more H2O.
This leads to decreased osmolarity (saltiness) of the ICF = disrupts cellular function
symptoms mainly effect neurological function - confusion, lethargy, headache, dizziness, vomiting, severe cases of coma or death
What is Diabetes Mellitus type 1 and 2 characterized by?
results from absolue or functional deficiency of circulating insulin - characterized by hyperglycemia
*because glucose is osmotically active, hyperglycemia leads to increased osmolarity in the ECF -causing intracellular dehydration.
What are the classic symptoms of diabetes mellitus?
polyuria (glucose in urine)
intracellular and extracellular dehydration
increased thirst
What does Tonicity measure?
tonicity is a measure of the osmotic pressure gradient of two solutions separated by a semipermeable membrane - it is influenced only by solutes that cannot cross the plasma membrane
i.e) hypertonic, isotonic, or hypotonic
What occurs when a RBC is placed in a hypertonic solution?
a hypertonic solution has an osmotically effective concentration which is greater than that of ECF - therefore the RBC loses water
What are the three principle forms of intravenous solutions given?
Colloid solution = hypertonic to reduce edema
crystalloid solutions = (can be isotonic to replace salt loss, hypotonic to correct hyperosmolar state, or hypertonic to correct overhydration and expland plasma volume)
blood products
What class intravenous fluid is most commonly used?
Crystalloids
Isotonic saline is administered to patients with… ?
low ECF volume (dehydrated) - it will distribute throughout the ECF increasing the ECF volume without altering the ECF osmolarity
hypertonic solutions are given to patients who…?
to patients whose plasma osmolarity is low and as a result, water has moved into cells (overhydration)
Hypotonic solutions are given to whom?
patients whose body fluids are hyperosmotic -
Why might a colloid be used instead of a hypertonic crystalloid solution?
They have a high molecular weight so they do not cross semipermeable membranes
b/c of their high osmolarity, they can exert an osmotic force across the wall of capillaries
initially they stay almsot entirely in the intravascular space for longer periods of time - reducing the ICF that has build up in edema patients
