Total body water constitute what percentage of Body Weight
**Core Concept**
Total body water (TBW) is a vital physiological parameter that represents the total amount of water present in the human body. It is essential to understand the distribution of TBW in different body compartments to comprehend various physiological processes, including electrolyte balance, circulation, and thermoregulation.
**Why the Correct Answer is Right**
The correct answer is B. 60% because approximately 60% of an adult's body weight is composed of water. This value can vary depending on factors such as age, sex, body composition, and hydration status. The majority of TBW is distributed in two main compartments: intracellular fluid (ICF) and extracellular fluid (ECF). ICF accounts for approximately 40% of TBW and is mainly found within cells, while ECF accounts for approximately 20% of TBW and is found in the interstitial space and blood vessels.
**Why Each Wrong Option is Incorrect**
**Option A:** 80% is incorrect because it overestimates the percentage of body weight that is composed of water. This value is more characteristic of newborns and infants, who have a higher water content due to their higher proportion of body fat and lower body mass.
**Option C:** 33% is incorrect because it significantly underestimates the percentage of body weight that is composed of water. This value is more characteristic of certain organs, such as the brain, which has a relatively high water content.
**Option D:** 25% is incorrect because it is a gross underestimation of the percentage of body weight that is composed of water. This value is more characteristic of certain dry tissues, such as bone, which has a relatively low water content.
**Clinical Pearl / High-Yield Fact**
It's essential to note that the percentage of body weight composed of water can vary significantly depending on factors such as age, sex, and body composition. For example, athletes may have a higher percentage of body weight composed of water due to increased muscle mass, while the elderly may have a lower percentage due to decreased muscle mass and increased body fat.
✓ Correct Answer: B. 60%