Fluids compartments and solutes Flashcards
What are anions and examples?
- Organic phosphate is the main intracellular anion
- proteins
What are cations?
e.g.
Na+ - main in plasma
K+ - main intracellular
What is osmolarity?
a measure of the concentration of all the solute particles in a solution
final state: intracellular osmolarity = outside osmolarity the “strength” of a solution as it affects the final cell volume.
What is tonicity?
-the “strength” of a solution as it affects the final cell volume.
- depends on both:
1) cell membrane permeability
2) the solution composition
What is hypertonic solution?
the osmolarity of the impermeant solutes outside the cell > than those inside the cell
i.e. cell shrinks
What is a hypotonic solution?
osmolarity of the impermeant solutes outside the cell < than those inside the cells
i.e. cell swells
What is an isotonic solution?
the osmolarity of the impermeant solutes outside the cell = inside the cell
i.e. cell volume remains unchanged
Why don’t cells burst?
- Na+k+ATPase maintains conc of Na+ ions much lower inside cell than outside
- ATPase makes membrane “effectively impermeable” to Na+ because any Na+ that diffuses down Na+ gradient is pumped out again so no net movement of Na+.
What is important to consider in transplantation?
- cooling of the tissue/organ to slow ischaemic changes
- tissues are perfused with cold solutions so that it reduces its deterioration + hypothermia cell swelling
What are the three main factors to reduce cell swelling in UW-infused tissues?
1) Lack of Na+ or Cl- (therefore no influx possible).
2) Presence of extracellular impermeant solutes (lactobionate ions, raffinose).
3) Presence of a macromolecular colloid (starch)
What is exchanged across capillary wall like?
- plama proteins cause an osmotic pressure known as the colloid osmotic pressure (COP) inside a capillary so water drawn in
- flow of blood through the vessel also generates a hydrostatic pressure inside the vessel which is greater than that in the tissues surrounding
- balance of these opposing forces cause molecues to be pushed out i.e. if HP > OP
What is an oedema?
“accumulation of fluids within tissues”
leakage of plasma into the interstitium (e.g. due to leaky walls) too fast for the lymph system to clear it out → fluid accumulates in the interstitial space
What is an inflammatory oedema?
Swelling occurs because the rate of leakage from the vessels is greater than the rate at which the lymphatics can drain it
What is a hydrostatic oedema?
high bp = high hydrostatic pressure = more fluid pushed out of the vessels = accumulation of fluids = swelling
what happens to the lymph system in elephantiasis?
parasitic worms can block lymphatic vessels = preventing drainage of the lymph = swelling
