ECF is how much part of total body water –
**Core Concept**
The extracellular fluid (ECF) is a compartment of the body's total water content, which plays a crucial role in maintaining various bodily functions, including blood pressure, pH balance, and electrolyte homeostasis. The ECF is the fluid component outside the cells, making up a significant portion of the body's total water.
**Why the Correct Answer is Right**
The ECF accounts for approximately 20% of the total body weight, which is roughly two-thirds of the total body water. This is because the ECF includes plasma, interstitial fluid, and transcellular fluid, which are essential for maintaining the body's homeostasis. The high water content in the ECF is necessary for blood volume, blood pressure, and nutrient transport to cells.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the ECF is not less than 10% of the total body weight. Although the ECF is a significant component, its proportion is relatively high compared to the intracellular fluid (ICF).
**Option B:** This option is incorrect because the ECF is not more than 30% of the total body weight. While the ECF is a substantial portion, its proportion is not as high as 30%.
**Option C:** This option is incorrect because the ECF is not exactly 50% of the total body weight. Although the ECF is a significant component, its proportion is not exactly 50%.
**Clinical Pearl / High-Yield Fact**
The ECF is a dynamic compartment that adjusts to changes in blood volume, electrolyte balance, and fluid status. It is essential to understand the ECF's proportion and composition to manage various clinical conditions, such as dehydration, hypertension, and electrolyte imbalances.
**Correct Answer:** C. 20%