Fluid compartments of the body

Question 1

What percentage of the fluid in the body is intracellular and extracellular and convert this litres?

Answer 1

55% = 23L

Extracellular: 45% 19L

Question 2

What percentage of the fluid in the body is interstitial (fluid between cells)

Answer 2

36% = 15L

Question 3

What other parts make up the extracellular and what is the percentage composition in each

Answer 3

Blood plasma (7%)= 3L
Transcellular fluid (2%) = 1L e.g. cerebrospinal, ocular, synovial fluid

Question 4

What are the main cations and anions found inside and outside cells?

Answer 4

Na+, K+, Ca2+ Cl-, Organic Phosphates, Proteins

Question 5

What is the concentration, in mmol/l, of Na+, K+ and Ca2+ found inside and outside the cells?

Answer 5

Na+ inside: 10mmol, outside: 150mmol
K+ inside: 150mmol, outside: 5mmol
Ca2+ inside: 10^-4mmol, outside: 2mmol

Calcium is an important signalling ion- it is present in very low concentrations inside cells but there are some compartments which store calcium (e.g. ER)

MORE OUTSIDE:

Na+
Ca2+

More INside:
K+

Question 6

What is the concentration, in mmol/l, of Cl-, Organic Phosphates and proteins found inside and outside the cells?

Answer 6

Organic phosphates: Main intracellular anions

Protein – outside:1, inside 2
Cl-outside: 110, inside: 5
Organic Phosphates outside: 5, inside: 130

More outside:

Cl-

More inside:

Protein
Organic phosphate

Question 7

What is the pH inside and outside cells?

Answer 7

7.4 outside 7.1 inside

Question 8

What are proteins

Answer 8

Anions which are present in low concentration but have a HIGH charge

Question 9

Define osmolarity

Answer 9

The concentration of a solution expressed as the total number of solute particles per litre.

Question 10

What is the osmolarity in the EC and IC and are there any exceptions?

Answer 10

Osmolarity is the same- exception is some parts of the kidney.

Question 11

In which direction does water move due to osmosis?

Answer 11

Towards the area of higher osmolarity

Question 12

What feature does osmolarity not take into account?

Answer 12

Membrane permeability to ions

Question 13

Define tonicity

Answer 13

The strength of a solution as it affects final cell volume

Question 14

What does tonicity depend on

Answer 14

Cell membrane permeability and

Solution composition

Question 15

What do hypertonic, hypotonic and isotonic solutions do?

Answer 15

Hypertonic – make cells shrink Hypotonic – make cells swell Isotonic – cells don’t change

Question 16

What feature do real cells have which prevents them from bursting due to having a higher osmolarity inside the cell than outside?

Answer 16

They have sodium-potassium pumps – maintains a lower concentration of sodium inside than outside

Question 17

What causes the osmotic pressure in capillaries?

Answer 17

Osmotic pressure due to plasma proteins (colloid osmotic pressure (COP) draws water in): more protein inside than outside the vessel

Question 18

What two forces affect the movement of fluid between the capillary and the interstitial space?

Answer 18

Colloid Osmotic Pressure and Hydrostatic Pressure(due to blood pressure).
Hydrostatic pressure > COP = plasma leakage out

Hydrostatic pressure < COP = flow into vessel

Question 19

What is oedema?

Answer 19

Abnormal collection of fluid in the interstitium due to the leakage of fluid from capillaries which causes swelling(leakage exceeds capacity of the lymphatics to collect and return it to the circulation

Question 20

What is the role of the lymphatic system

Answer 20

Returns interstitial fluid to the blood circulation. Lymph fluid returns to the circulation in nodes (50%) or via the lymphatic ducts in the subclavian region(50%)

Question 21

Under normal, healthy conditions for a 70kg man, how much fluid leaks from blood vessels into interstitial spaces?

Answer 21

A significant amount (8L/day)

Question 22

Which solute is normally abundant inside cells, moderately abundant in blood plasma, but low in interstitial fluids?

Answer 22

Protein

Question 23

If you treat mammalian cells with a drug that inhibits the Na+/K+ exchange pump, what will be the effect on cell size?

Answer 23

The cells will swell significantly