Final answer:
The human body contains approximately 50% intracellular fluid and 20% extracellular fluid of the total body weight, with the main compartments of the ECF being interstitial fluid and blood plasma.
Step-by-step explanation:
The body contains intracellular fluid (ICF) and extracellular fluid (ECF). The intracellular fluid makes up about 50% of the total body weight, and represents water contained within cells, enclosed by their plasma membranes. On the other hand, the extracellular fluid accounts for about 20% of the body weight, with around 15% being interstitial fluid (the fluid that surrounds cells that are not blood cells) and approximately 5% being blood plasma. The fluids are essential for various physiological processes, acting as a medium for transporting nutrients, gases, and wastes, and are separated by selectively permeable cell membranes which help in regulating the passage of materials.