Body fluids
Human body is primarily composed of water. In male, about 60% of body weight is water (and in female, it is about 55%). Total body water (TBW) decreases with age. Adipose tissue is low in water content; thus, obese individuals have less body water than normal weight individuals.TBW is divided into two major compartments: intracellular fluid (ICF) and extracellular fluid (ECF). The ICF compartment represents fluid contained within all cells in the body (approximately 65% of TBW). The ECF compartment includes all fluids outside of cells (approximately 35% of TBW).
ECF is further divided into:
a. Blood plasma (blood without cells) about 20% of ECF
b. Interstitial fluid (ISF) (fluid between cells) about 70% of ECF
c. Transcellular fluid (synovial, intraocular, pericardial, cerebrospinal, and epithelial fluids) about 10% of ECF
Exchange of fluid and solutes through capillary membrane
Four forces control movement of fluid through capillary wall called Starling forces:1- Capillary hydrostatic pressure Pc moves water out of capillary
2- Capillary osmotic pressure πc moves water into capillary
3- Tissue space hydrostatic pressure Pif moves water out of tissue space
4- Tissue space osmotic pressure πif moves water into tissue space
Lymphatic system
Some excess tissue fluid containing electrolytes and some escaped proteins is collected by lymphatic capillaries. Tissue fluid contained within lymphatic vessels is calledlymph. Lymph returns to the systemic venous blood when the major lymphatic vessels enter subclavian veins in shoulder region.
Edema
Edemais an abnormal accumulation of fluid in the HYPERLINK "http://en.wikipedia.org/wiki/Interstitium" \o "Interstitium" interstitium or in one or more cavities of the body. It is clinically shown as HYPERLINK "http://en.wikipedia.org/wiki/Swelling_(medical)" \o "Swelling (medical)" swelling.
Causes of edema are:
1increased pressure difference (e.g. hypertension and pregnancy, hypoalbuminemia, liver cirrhosis and inflammation). 2increased blood vessel wall permeability (e.g. inflammation and allergy) and 3obstruction of lymphatic system (e.g. tumors or surgical removal of lymph nodes).