Understanding the Body's Fluid Compartments: Intracellular, Interstitial & Plasma

1. Intracellular fluid is the fluid inside cells. It makes up about two-thirds of the body's total fluid volume.

2. Extracellular fluid is the fluid outside cells. It includes interstitial fluid, which is the fluid between cells, and plasma, which is the fluid portion of blood. Extracellular fluid makes up about one-third of the body's total fluid volume.

3. Transcellular fluid is the fluid that moves across epithelial cell layers. It includes cerebrospinal fluid, synovial fluid, and gastrointestinal fluid. Transcellular fluid makes up a small percentage of the body's total fluid volume.