Final answer:
The primary fluid compartments in our bodies are intracellular fluid (ICF), the fluid within cells, and interstitial fluid (IF), which bathes cells exterior to blood vessels. Together, they compromise most of the body's fluid content.
Step-by-step explanation:
The two compartments that make up the primary fluid compartments in our bodies are intracellular fluid (ICF) and interstitial fluid (IF). Intracellular fluid refers to the fluid within cells, making up about 50% of the total body weight. Interstitial fluid, on the other hand, is the part of the extracellular fluid (ECF) that surrounds and bathes all cells not in the blood, accounting for approximately 20% of the body weight.
The largest amount of water in the body is found within the intracellular fluid, and the second largest volume is the interstitial fluid. These two compartments are separated by the cell membrane, which allows certain substances to diffuse through while being impermeable to others. The interstitial fluid is very similar to the blood plasma, and they both communicate through capillary walls.