Final answer:
Extracellular fluid consists of interstitial fluid and blood plasma, both of which are fundamental for physiological processes like nutrient exchange, ion balance, and pH regulation.
Step-by-step explanation:
The extracellular fluid (ECF) is composed of various fluid compartments outside the cells, which include interstitial fluid, blood plasma, and other bodily fluids such as lymph. Interstitial fluid bathes and surrounds the cells of multicellular animals and is a significant component of the ECF.
It is similar in composition to plasma and allows for the exchange of nutrients and waste between cells and the blood. Blood plasma, another component of the ECF, travels through blood vessels, carrying cells, proteins, electrolytes, and other substances crucial for the body's function.
These components of the ECF are vital in maintaining physiological processes such as osmotic balance, ion balance, and pH regulation. The concentration of cations in the ECF is relatively low, but they play a critical role in cellular functions. Thus, it is clear that extracellular fluid consists of both interstitial fluid and plasma, not just interstitial fluid alone.