Body fluids, bodily fluids, or biofluids, sometimes body liquids, are liquids within the body of an organism.[1] 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 (52–55%).[2][3] The exact percentage of fluid relative to body weight is inversely proportional to the percentage of body fat. A lean 70 kg (150 lb) man, for example, has about 42 (42–47) liters of water in his body.
The total body of water is divided into fluid compartments,[1] between the intracellular fluid 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 interstitial fluid compartment is divided into the lymphatic fluid compartment – about 2/3, or 8 (6–10) liters, and the transcellular fluid compartment (the remaining 1/3, or about 4 liters).[4]
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.[5]
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.[7] In medical contexts, it is a specimen taken for diagnostic examination or evaluation, and for identification of disease or condition.[8]