Final answer:
The extracellular and intracellular fluid compartments must be regulated precisely for optimal cellular function and water balance, with the intracellular fluid making up roughly 50% and extracellular fluid including substances like interstitial fluid and plasma.
Step-by-step explanation:
The extracellular and intracellular fluid compartments must be regulated within precise limits to ensure proper cellular functions and overall water balance. The intracellular fluid (ICF) is the fluid contained within the cells, making up about 50% of the total body weight. The extracellular fluid (ECF) is the fluid outside the cells and includes interstitial fluid (IF) and plasma. Interstitial fluid bathes and surrounds cells, providing nutrients and waste removal. The balance of water and solute concentrations in these compartments is crucial for maintaining cellular integrity and function. The movement of water and solutes between these compartments is facilitated by passive transport mechanisms like diffusion and active transport mechanisms requiring energy.