The extra-cellular fluid content in our body is around?

Appeared in: DSSSB - 29 August 2019 (Shift-1)

Explanation

In a standard 70 kg adult, total body water is about 60% of body weight, equating to approximately 42 litres.
This total body water is divided into two main compartments: Intracellular Fluid (ICF) and Extracellular Fluid (ECF).
The ECF comprises about one-third of the total body water, which calculates to approximately 14 litres (42 L / 3).
Among the given choices, 12 litres is the closest and most commonly accepted value for the ECF volume in textbooks and clinical contexts.

Option A: 3 litres represents the volume of plasma, which is a component of the extracellular fluid, not the total ECF volume.
Option C: 9 litres is an inaccurate value and does not correspond to a major fluid compartment volume.
Option D: 6 litres is closer to the total blood volume (plasma + blood cells), which is approximately 5-6 litres in an adult. It is not the volume of the ECF.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Body Fluid Compartments as background academic context rather than a clinical decision trigger.
Understanding the volumes of different fluid compartments is fundamental for nurses to manage fluid and electrolyte balance.
It is crucial for calculating fluid requirements, administering intravenous (IV) therapy, and assessing for signs of dehydration (ECF volume deficit) or fluid overload (ECF volume excess).
For instance, a patient with severe diarrhea loses significant amounts of ECF, leading to hypovolemia. A nurse must be able to recognize the signs (e.g., tachycardia, hypotension) and intervene appropriately with fluid replacement.

How to Approach the Question

First, recall the basic principles of body fluid distribution. Remember that Total Body Water (TBW) is about 60% of an adult's body weight.
Next, remember the 'two-thirds, one-third' rule: about two-thirds of TBW is inside the cells (Intracellular Fluid - ICF) and one-third is outside the cells (Extracellular Fluid - ECF).
Apply this to a standard 70 kg person: TBW = 70 kg * 0.60 = 42 litres.
Calculate the ECF volume: ECF = 1/3 * 42 litres = 14 litres.
Compare this calculated value to the given options. The option '12 litres' is the closest and most common textbook approximation for ECF.
Eliminate other options by identifying what they represent: 3 litres is plasma volume, and 6 litres is closer to total blood volume.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 1 pp. 85-87, 84-86

E6 Medicine Davidson Principles Practice 24e p. 369-371

Practise the full DSSSB - 29 August 2019 (Shift-1)

Attempt every question from this paper in a timed mock, then review the full solution for each one.