Volume of ICF in body
**Core Concept**
The intracellular fluid (ICF) is a component of the total body water, comprising the fluid within cells, while the extracellular fluid (ECF) is the fluid outside the cells. The total body water is approximately 60% of the body weight, with the ICF making up about 2/3 of this total.
**Why the Correct Answer is Right**
The ICF volume is approximately 28 liters (28,000 ml or 28 L) in an average adult human, accounting for about 2/3 of the total body water. This volume is maintained by the balance between the influx of ions and water into the cell and the efflux of ions and water out of the cell. The cell membrane is selectively permeable, allowing certain ions and molecules to pass through while restricting others. The sodium-potassium pump, an active transport mechanism, helps to maintain the concentration gradient of sodium and potassium ions across the cell membrane, which in turn helps to regulate the ICF volume.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the ECF volume is approximately 17 liters (17,000 ml or 17 L), not the ICF volume.
**Option B:** Incorrect because the ICF volume is approximately 28 liters, not 40 liters.
**Option C:** Incorrect because the ICF volume is approximately 28 liters, not 20 liters.
**Clinical Pearl / High-Yield Fact**
The ICF volume is regulated by various mechanisms, including the sodium-potassium pump, which is essential for maintaining proper cellular function and overall health.
**Correct Answer: C. 28 L**