Fluid compartments of the body Flashcards
What percentage of the fluid in the body is intracellular and extracellular and convert this litres?
55% = 23L
Extracellular: 45% 19L
What percentage of the fluid in the body is interstitial (fluid between cells)
36% = 15L
What other parts make up the extracellular and what is the percentage composition in each
Blood plasma (7%)= 3L Transcellular fluid (2%) = 1L e.g. cerebrospinal, ocular, synovial fluid
What are the main cations and anions found inside and outside cells?
Na+, K+, Ca2+ Cl-, Organic Phosphates, Proteins
What is the concentration, in mmol/l, of Na+, K+ and Ca2+ found inside and outside the cells?
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+
What is the concentration, in mmol/l, of Cl-, Organic Phosphates and proteins found inside and outside the cells?
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
What is the pH inside and outside cells?
7.4 outside 7.1 inside
What are proteins
Anions which are present in low concentration but have a HIGH charge
Define osmolarity
The concentration of a solution expressed as the total number of solute particles per litre.
What is the osmolarity in the EC and IC and are there any exceptions?
Osmolarity is the same- exception is some parts of the kidney.
In which direction does water move due to osmosis?
Towards the area of higher osmolarity
What feature does osmolarity not take into account?
Membrane permeability to ions
Define tonicity
The strength of a solution as it affects final cell volume
What does tonicity depend on
Cell membrane permeability and
Solution composition
What do hypertonic, hypotonic and isotonic solutions do?
Hypertonic – make cells shrink Hypotonic – make cells swell Isotonic – cells don’t change
What feature do real cells have which prevents them from bursting due to having a higher osmolarity inside the cell than outside?
They have sodium-potassium pumps – maintains a lower concentration of sodium inside than outside
What causes the osmotic pressure in capillaries?
Osmotic pressure due to plasma proteins (colloid osmotic pressure (COP) draws water in): more protein inside than outside the vessel
What two forces affect the movement of fluid between the capillary and the interstitial space?
Colloid Osmotic Pressure and Hydrostatic Pressure(due to blood pressure).
Hydrostatic pressure > COP = plasma leakage out
Hydrostatic pressure < COP = flow into vessel
What is oedema?
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
What is the role of the lymphatic system
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%)
Under normal, healthy conditions for a 70kg man, how much fluid leaks from blood vessels into interstitial spaces?
A significant amount (8L/day)
Which solute is normally abundant inside cells, moderately abundant in blood plasma, but low in interstitial fluids?
Protein
If you treat mammalian cells with a drug that inhibits the Na+/K+ exchange pump, what will be the effect on cell size?
The cells will swell significantly
