Fluid Compartments

Question 1

How much of the body is fluid?

Answer 1

Fluid 55-60%

Question 2

Where is the fluid?

Answer 2

• Majority intracellular e.g fluid in muscle
• Out of EC fluid most is interstitial
• 7% is blood plasma (like interstitial but plasma has more protein)
• 2% is transcellular fluid e.g cerebrospinal, ocular, synovial
• ECF mostly compartmentalized by barriers
• Also separated by layers of cells by forming junctions between one another

Question 3

What do epithelial and endothelial barriers separate?

Answer 3

Epithelial: separate various interstitial spaces
Endothelial: line blood vessels and main barer separating blood (plasma) and interstitial fluid

Question 4

Where is the position of the major cations?

Answer 4

• Sodium in high concentrations ECF
• Potassium in high concentration ICF
• Calcium is a signaling ion. Low concentration in cell but some compartments (e.g ER) store it

Question 5

Where is the position of the major anions?

Answer 5

• Chloride in high concentration ECF
• Organic Phosphates in high concentration ICF
• Proteins in low concentration but have high charge

Question 6

What is the pH comparison outside and inside cells?

Answer 6

• slightly higher inside of cell

Question 7

What are the modes of passive transport?

Answer 7

• via lipid or pore on carrier

Question 8

What are the modes of active transport?

Answer 8

• Primary: on carrier e.g Na/K pump
• Secondary: on carrier, downhill movement of 1 solute coupled to uphill movement of another (exploiting potential energy of sodium-glucose symport)

Question 9

What can pass through endothelial pores?

Answer 9

○ Plasma proteins generally can’t pass through pores and membrane
○ Small water soluble molecules pass via pores
○ Lipid soluble pass
○ Exchangeable proteins moved via vesicles

Question 10

Define osmolarity?

Answer 10

• same both intracellular and extracellular
• Osmolarity of solution will be about number of particles/ions involved
• Measure of concentration of all solute particles in solution

Question 11

Define tonicity?

Answer 11

• defines strength of solution as it affects final cell volume

1. Membrane permeability
2. Solution composition

Question 12

Define hypotonic, hypertonic?

Answer 12

Hypertonic: cell shrinks
- Osmolarity of impermeant solutes outside greater than inside

Hypotonic: cell swells
- Osmolarity of impermeant solutes inside greater than outside

Question 13

What maintains potential in a real cell?

Answer 13

Sodium-Potassium pump

Question 14

What two pressures determine fluid composition?

Answer 14

Colloid osmotic pressure (COP): osmotic pressure because plasma protein
- Draws water in

Hydrostatic Pressure: circulatory system pressure exerted by volume of blood when confined in blood vessel
- Pushes water out

Question 15

Define oedema?

Answer 15

swelling of tissue because excess interstitial fluid

Question 16

What occurs during oedema?

Answer 16

• Increased capillary permeability of capillary walls to plasma proteins - increased pore size
• Lymph fluid returns to circulation at nodes (50%) or lymphatic ducts in subclavian regions (50%)
• Odema when leakage into intertituum exceeds capacity of lymphatic vessels to collect returns to circulation
• Usually inflammation sign e.g infectious and inflammatory stimuli