THE BODY FLUIDS:

Water with its solvents needed for the health of the cells is termed body fluid and this fluid is partly inside and partly outside the cells. Intracellular fluid forms 50% of the body-weight. It lies within the cells and certain electrolytes including potassium  and phosphates and food materials like glucose and amino-acids. Enzyme action is constant with in the cell breaking down and building up as in all metabolism to maintain a balance.

Extracellular / interstitial fluid represents 30% of the water in the body (abt 12litres). It is the medium in which the cell live obtaining from it salts, food and oxygen and passing into it their waste products, Blood Plasma forms 5% of body-weight (abt 3 litres) and it is the transport system which serves the cells through the medium of the extracellular fluid.

OEDEMA:

Oedema is waterlogging of the tissues due to a breakdown of the delicate balance described above. It can obviously arise from one of four reasons:

(1) Too high a mechanical hydrostatic pressure in the capillaried as happens, for eg. if the venous drainage is          blocked.

(2) Too low an osmotic pressure due to the insufficient plasma protein, particularly albumin.

(3) Blockage of the lymphatics.

(4) Damage of the capillaries wall so that the plasma proteins leak out into the tissue and cause an osmotic pressure opposing the osmotic pressure of the blood stream.