Water, fluids, spaces and compartments

Question 1

What are the two primary fluid compartments in the body?

Answer 1

ICF
ECF

Question 2

What three compartments make up the ECF?

Answer 2

Interstitial fluid
Intravascular fluid
Transcellular fluid

Question 3

Define oedema.

Answer 3

Abnormal accumulation of fluid beneath the skin, or in one or more cavities of the body

Question 4

How many litres of fluid are present in the ICF?

Answer 4

28L

Question 5

How many litres of fluid are present in the interstitial fluid? (ECF)

Answer 5

10.5L

Question 6

How many litres of fluid are present in the intravascular fluid? (ECF)

Answer 6

3.5L

Question 7

What does mass =?

Answer 7

Concentration X volume

Question 8

What is a plasma compartment tracer?

Answer 8

RISA

Question 9

What is an extracellular compartment tracer?

Answer 9

Mannitol or inulin

Question 10

What is a total body volume tracer?

Answer 10

THO

Question 11

What makes up blood volume?

Answer 11

Red blood cells and plasma

Question 12

What is Haematocrit?

Answer 12

Fraction of the blood that is RBCs

Question 13

What is the equation for blood volume?

Answer 13

Plasma volume/ 1 - Hct

Question 14

What is the initial body access point for ingested nutrients and exit point for body’s waste product?

Answer 14

Plasma water

Question 15

How are all cells bar blood cells accessed?

Answer 15

Interstitial space

Question 16

How do solutes enter/leave the body?

Answer 16

Via ECF

Question 17

How do kidneys regulate water excretion

Answer 17

Diffuse across cell plasma membrane via aquaporins

Question 18

What can alter type/number of aquaporins?

Answer 18

ADH

Question 19

Where are numerous aquaporins expressed?

Answer 19

Late distal tubules
Collecting tubules

Question 20

What does movement between body fluid compartments depend on?

Answer 20

Endothelial cell wall

Question 21

What substances require specific integral membrane proteins to cross cell plasma membrane?

Answer 21

Small/large uncharged polar molecules
Ions

Question 22

What are the main drivers of solute movement between intracellular and interstitial fluid compartments?

Answer 22

Osmotic pressure and electrochemical gradients

Question 23

Define osmotic pressure.

Answer 23

Pressure that must be applied to a solution to prevent net flow of water into it

Question 24

What are the main drivers of solute movement between interstitial and plasma compartments?

Answer 24

Hydrostatic pressure and oncotic pressure

Question 25

How are charges separated across a plasma membrane?

Answer 25

Electrical force drives +ve ions into cell and -ve ions out

Question 26

What is hydrostatic pressure?

Answer 26

Pressure exerted by a fluid at equilibrium due to force of gravity

Question 27

What is oncotic pressure?

Answer 27

Type of osmotic pressure generated by impermeable proteins in solution
eg. large plasma proteins pull water into capillaries

Question 28

What does water distribution in body compartments depend primarily on?

Answer 28

Conc. ion of electrolytes

Question 29

What is normal osmolality?

Answer 29

290mOsm

Question 30

What is tonicity?

Answer 30

Fluctuations in cell volume

Question 31

What is an ineffective osmole?

Answer 31

Substance that, although osmotically active, can easily distribute across body compartments and so does not cause fluid shifts i.e. urea

Question 32

How can fluid be lost?

Answer 32

Skin
Diarrhoea
diuretics
oedema

Question 33

What happens in isosmotic dehydration?

Answer 33

ECF volume decreases
Osmolality of ECF does not change
ICF volume and osmolality does not change
eg. GIT fluids

Question 34

What happens in hyperosmotic dehydration?

Answer 34

Loss of water in excess of solute
ECF volume decrease
ECF osmolality increases
ICF volume decrease (moves into ECF)
Osmolalities equalized