Week 1 Physiology - Body Fluids

Question 1

What is ECF? What are its subdivisions?

Answer 1

Fluid surrounding cells, supplies nutrients and absorbs waste products.

1. Interstitial fluid
2. Plasma

Question 2

What is osmosis?

Answer 2

Diffusion of solvent molecules into a region in which there is a higher concentration of solute to which the membrane is impermeable

i.e. H2O moving across to area of higher Na+ to maintain an equal concentration gradient

Question 3

What is osmotic pressure?

Answer 3

Number of particles over volume

Question 4

What are osmoles?

Answer 4

The gram molecular weight of a substance divided by the number of freely moving particles that each molecule liberates in solution

i.e. one mole of NaCl –> Na+ and Cl- = 2osm

Question 5

What’s the difference between osmolality and osmolarity?

Answer 5

OsmolaRity = osmoles/litRe

Osmolality = osmoles/kg

Question 6

What is simple diffusion?

Answer 6

Process by which gas/substance expands because of motion of its particles, to fill available volume.

From high to low concentration, and rate to equilibrium is dependent on diffusion distance

Question 7

What is tonicity?

Answer 7

Osmolality of a solution relative to plasma

Question 8

What percentage of body water is ICF vs ECF?

Answer 8

ICF = 66%, ECF = 33%

Question 9

What % of body weight is water vs protein vs fat vs minerals?

Answer 9

Water 60%
Fat 15%
Protein 18%
Minerals 7%

**Total blood volume approx 8% body weight

Question 10

What is a mole?

Answer 10

6x10^23 molecules

Question 11

What is molecular weight?

Answer 11

Ratio of mass of 1 molecule to the mass of 1/12th mass of an atom of Carbon-12

Question 12

What is an equivalent?

Answer 12

1 mol of ionised substance divided by its valence

i.e. 1 equivalent of Na+ = 23g (1 valence electron) where 1 equivalent of Ca2+ = 40g /2 = 20g

Question 13

What is the intracellular vs extracellular concentration of Na+?

Answer 13

Intracellular = 15mmol/L
Extracellular = 150mmol/L

Question 14

What is the intracellular vs extracellular concentration of K+?

Answer 14

Intra = 150mmol/L
Extra = 5.5 mol/L

Question 15

What is the intracellular vs extracellular concentration of Cl-?

Answer 15

Intra = 9 mol/L
Extra 125 mol/L

Question 16

How are ketone bodies formed?

Answer 16

Fatty acids broken down to Acetyl-CoA –> citric acid cycle, undergoes beta-oxidation.

Acetyl CoA can condense to aceto-acetyl-CoA and be metabolised in liver to form acetoacetate, which can be metabolised in the liver.

Beta-hydroxybutarate and acetone not really metabolised well hepatically and so diffuse into circulation