Fluid Compartments and Solutes Flashcards
What is the difference between plasma and interstitial fluid?
Plasma has higher protein content
Which ions does plasma contain the most of?
- Na+
- Cl-
Which ions does cytoplasm contain the most of?
- K+
- Organic phosphates —> demand for ATP, signalling, cell activation
Which ions does plasma contain the least of?
- Free Ca2+
- Protein (anion)
Which ions does cytoplasm contain the least of?
- Free Ca2+
- Protein (anion)
What are the 7 differences between plasma and cytoplasm?
Plasma:
1. Higher Na+
2. Lower K+
3. Higher Ca+
4. Higher Cl-
5. Lower organic phosphates
6. Lower protein
7. Higher pH (lower H+ conc)
What unit is used for ion concentrations in body fluids?
mmol/L
What is the difference between plasma and cytoplasm Na+ concentration?
Higher in plasma
- 150 vs 10
What is the difference between plasma and cytoplasm K+ concentration?
Higher in cytoplasm
- 5 vs 150
What is the difference between plasma and cytoplasm free Ca2+ concentration?
Higher in plasma
- 2 vs 10^-4
What is the difference between plasma and cytoplasm Cl- concentration?
Higher in plasma
- 110 vs 5
What is the difference between plasma and cytoplasm phosphate concentration?
Higher in cytoplasm
- 5 vs 130
What is the difference between plasma and cytoplasm protein concentration?
Higher in cytoplasm
- 1 vs 2
What is the difference between plasma and cytoplasm pH?
Higher is plasma
- 7.4 vs 7.1
What is osmolarity?
Measure of concentration of all solute particles in a solution
How do you calculate osmolarity?
Σ osmoles
= Σ (concentration x no. ions in compound)
What is the unit of osmolarity?
mosm/L (milliosmoles per litre)
What is the osmolarity of plasma?
285 mosm/L
What is the osmolarity of cytoplasm?
285 mosm/L
In which organ is the cytoplasm osmolarity different from plasma?
Kidney —> filtration
What is diffusion?
Movement of solutes down conc grad till equilibrium
What is osmosis?
Movement of water down own grad (to higher osmolarity)
What are osmoles?
Moles of solute contributing to osmotic pressure
How does osmolarity affect cells?
Affects cell volume —> affect cell function and survival
How does membrane permeability affect cytoplasm volume?
More impermeable to solutes —> more swelling
- because water still in
What is the limitation of osmolarity?
Doesn’t consider membrane permeability (too simple)
What is tonicity?
Relative strength of a solution
What are the 3 types of tonicity?
- Hypertonic
- Hypotonic
- Isotonic
What are hypertonic solutions?
Extracellular solution conc > intracellular
What are hypotonic solutions?
Extracellular solution conc < intracellular
What are isotonic solutions?
Extracellular solution conc = intracellular
What does a larger difference in intra vs extracellular fluid tonicity lead to?
More cell volume change —> more damage
Which enzyme prevents cells bursting and how?
Na+K+ATPase
- Maintains Na+ conc in cells lower than out (pumps excess Na+ out)
What are the 4 methods used by solutes to pass the plasma membrane?
- Simple diffusion
- Channel-mediated diffusion
- Transporter-mediated diffusion
- Active transport
Which solutes can pass the membrane via simple diffusion? (2)
- Gases (eg. O2, N2, CO2)
- Hydrophobic molecules (eg. steroids)
When is active transport used?
Transport solute against concentration gradient
- Uses ATP hydrolysis energy
What are the 2 conditions transplant tissue is stored in and why?
- Perfused with UW solution
- Maintains intracellular concentrations —> maintain cell volumes - 4°C
- Preventhypoxic injury
- but —> inactivates NA+K+ATPase —> stops Na+ out cells —> stops Cl- and H2O out cells —> would cause swelling + death —> need UW solution
What is UW solution?
University of Wisconsin solution
- Solution perfused into transplant tissues to prevent cell swelling
What are the 4 main features of UW solution?
- Lack Na+ and Cl-
- Extracellular impermeant solutes present
- Presence of marcomolecular colloid (starch)
- Antioxidants (allopurinol and glutathione present)
How does exchange into/out of blood vessels occur?
Via pores between endothelial cells
What volume of plasma leaves the blood per day?
8L
How often does all the blood plasma leave and return to the blood?
Every 9 hours
What is COP?
Colloid Osmotic Pressure
- Maintainance of osmotic pressure by larger molecules (eg. plasma proteins)
What is hydrostatic pressure?
Pressure exerted by the fluid’s weight
What is important about plasma proteins in exchange?
Too large to leave blood —> concentration regulates fluid entry/exit
What maintains blood osmotic pressure?
Plasma proteins
What is oedema?
Swelling due to accumulation of fluid in the interstitial space
What happens when blood hydrostatic pressure > osmotic pressure?
Fluid leaves blood
How is interstitial fluid redistributed?
Lymphatic vessels
What are the 6 steps of interstitial fluid recirculation?
- Starts in blood capillaries - highest pressure
- To interstitial fluid
- To lymph capillaries
- To lymph veins
- To lymph ducts (subclavian region or lymph nodes)
- To large veins - lowest pressure
When does oedema occur?
Fluid accumulates in interstitial space
What are 2 common examples of oedema?
- Insect bites - insect damages blood vessel —> fluid leaks out
- Hypertension - high NaCl conc of blood —> lower water potential —> more fluid leaves
What are 2 examples of compromised lymphatic function causing oedema?
- Breast cancer surgery - armpit lymph nodes lost —> lymphatic drainage doesn’t occur in arm
- Elephantiasis - parasitic worms block lymph vessels