Body fluids, bodily fluids, or biofluids are liquids within the human body. In lean healthy adult men, the total body water is about 60% (60-67%) of the total body weight; it is usually slightly lower in women. The exact percentage of fluid relative to body weight is inversely proportional to the percentage of body fat. A lean 70 kg (160 pound) man, for example, has about 42 (42-47) liters of water in his body.
The total body of water is divided between the intracellular fluid (ICF) compartment (also called space, or volume) and the extracellular fluid (ECF) compartment (space, volume) in a two-to-one ratio: 28 (28-32) liters are inside cells and 14 (14-15) liters are outside cells.
The ECF compartment is divided into the interstitial fluid volume - the fluid outside both the cells and the blood vessels - and the intravascular volume (also called the vascular volume and blood plasma volume) - the fluid inside the blood vessels - in a three-to-one ratio: the interstitial fluid volume is about 12 liters, the vascular volume is about 4 liters.
The vascular volume is divided into the venous volume and the arterial volume; and the arterial volume has a conceptually useful but unmeasurable subcompartment called the effective arterial blood volume.
Compartments by location
Body fluid is the term most often used in medical and health contexts. Modern medical, public health, and personal hygiene practices treat body fluids as potentially unclean. This is because they can be vectors for infectious diseases, such as sexually transmitted diseases or blood-borne diseases. Universal precautions and safer sex practices try to avoid exchanges of body fluids. Body fluids can be analyzed in medical laboratory in order to find microbes, inflammation, cancers, etc.
Clinical samples are generally defined as non-infectious human or animal materials including blood, saliva, excreta, body tissue and tissue fluids, and also FDA-approved pharmaceuticals that are blood products. In medical contexts, it is a specimen taken for diagnostic examination or evaluation, and for identification of disease or condition.
Methods of sampling of body fluids include:
- Blood sampling for any blood test, in turn including:
- Lumbar puncture to sample cerebrospinal fluid
- Paracentesis to sample peritoneal fluid
- Thoracocentesis to sample pleural fluid
- Amniocentesis to sample amniotic fluid