Fluid Compartments and Solutes

Question 1

What is the most plentiful cation in the plasma?

Answer 1

Sodium

Question 2

What is the most plentiful cation inside cells?

Answer 2

Potassium

Question 3

True or false: chlorine is found at much lower concentrations in plasma than in cells

Answer 3

False: chlorine is found at much higher concentrations in the plasma that inside cells

Question 4

What is the main intracellular anion?

Answer 4

Organic phosphate

Question 5

What can phosphorylation of proteins do?

Answer 5

Activate and inactivate them

Question 6

How does the pH of cell compare with plasma?

Answer 6

Cell is slightly more acidic (0.3 pH units)

Since pH is logarithmic it means the cell has twice the concentration of protons

Question 7

True or false: the osmolarity between the blood and intracellular compartment is identical

Answer 7

True: normally no significant osmotic effect

Exception-kidney

Question 8

Define diffusion

Answer 8

Spontaneous movement of a solute down a concentration gradient until the solute molecules reach an equilibrium

Question 9

Define osmosis

Answer 9

Movement of water down its own concentration gradient

It can change cell volume with consequences for cell function an survival

Question 10

Define osmolarity

Answer 10

Measure of the concentration of all the solute particles in a solution

Question 11

What is tonicity?

Answer 11

Defines the ‘strength’ of a solution as it affects the final cell volume
Depends on both cell membrane permeability and the solution composition

Question 12

What happens in a hypertonic solution?

Answer 12

Osmolarity of impermeant solutes outside the cell are greater than those inside
Water mover out
Cell shrinks

Question 13

What happens to a cell in hypotonic solutions?

Answer 13

Osmolarity of the impermeant solutes outside the cell is less than inside
Water moves in
Cell swells

Question 14

What happens to a cell in isotonic solution?

Answer 14

Nothing

Cell volume unchanged

Question 15

How are cell volumes maintained?

Answer 15

By actively pumping ions
E.g. in hypotonic solution
Na/K pump maintains the conc. of Na+ much lower inside cell
Makes membrane effectively impermeable to Na+
Intracellular and Extracellular osmolarity balance
(High conc of Na+ outside cell)

Question 16

How does university of wisconsin solution enhance organ preservation?

Answer 16

Reduces cell swelling

• lack of Na+ or Cl- (no influx possible)
• presence of Extracellular impermeant solutes
• presence of macromolecular colloid (starch)

Question 17

What is colloid osmotic pressure?

Answer 17

Osmotic pressure generated due to higher concentrations of plasma proteins inside the capillary that outside

Question 18

Why is there a tendency to ‘push’ molecules through the capillary pores?

Answer 18

Flow of blood through the vessel generated a hydrostatic pressure inside vessel greater than than of the tissues
Under normal condition this pressure results in net leakage from the capillary

Question 19

What is oedema?

Answer 19

Accumulation of fluids with tissues

Results due to an imbalance in the normal chuckle of fluid exchange

Question 20

What do lymphatic capillaries do?

Answer 20

Collect interstitial fluids destined to return to blood circulation to combat loss of plasma fluids
They have low internal pressure which results in net flow of fluids inwards

Question 21

How does lymph fluid return to circulation?

Answer 21

Via the lymphatic ducts in the subclavian region or via lymph nodes

Question 22

At what point does oedema occur?

Answer 22

When leakage of plasma into interstitium exceeds lymphatic capacity

Question 23

Why does oedema result from high blood pressure?

Answer 23

Increased pressure pushes more fluid out of vessels

Question 24

What causes elephantiasis?

Answer 24

Parasitic worms block lymphatic vessels preventing drainage