The major role in maintaining fluid balance in the body is performed by?

BCCL kharkhanda Staff Nurse - 2015

Applied Physiology

Easy

Appeared in: BCCL kharkhanda Staff Nurse - 2015

Explanation

The kidneys are the primary regulators of fluid and electrolyte balance, vital for maintaining homeostasis.
They filter approximately 180 liters of plasma daily, but excrete only 1 to 2 liters as urine, demonstrating their powerful ability to reabsorb and conserve water.
The kidneys selectively retain or excrete water and electrolytes in response to the body's needs.
This process is regulated by hormones, primarily antidiuretic hormone (ADH) and aldosterone, which control the amount of water and sodium reabsorbed back into the blood.

Option A: The liver's role is indirect. It produces albumin, a protein that maintains colloid osmotic pressure, which helps to keep fluid within the blood vessels. However, it does not directly filter or excrete excess fluid.
Option B: The heart's function is to pump blood. While adequate blood flow and pressure from the heart are essential for the kidneys to work (renal perfusion), the heart itself does not filter blood or regulate fluid volume.
Option C: The lungs contribute to fluid loss through exhalation (insensible water loss), but this is a relatively small, passive, and unregulated amount (around 300 mL/day). They cannot adjust this loss to maintain overall fluid balance.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Regulation of body fluid balance as background academic context rather than a clinical decision trigger.
A key nursing responsibility for patients with kidney issues or those at risk for fluid imbalance is the strict monitoring of fluid intake and output (I&O) and daily weights. A weight change of 1 kg is equivalent to a 1-liter fluid gain or loss.
In kidney failure, the body loses its ability to excrete fluid, leading to fluid volume excess, edema, hypertension, and electrolyte imbalances.
What if? If a patient has severe heart failure, the heart's weak pumping action reduces blood flow to the kidneys. This tricks the kidneys into thinking the body is dehydrated, causing them to retain sodium and water, which worsens the fluid overload and edema characteristic of heart failure.

How to Approach the Question

First, identify the core physiological concept in the question, which is 'fluid balance'.
Next, focus on the keyword 'major role'. This signals that you must compare the functions of the four organs listed and determine which one has the most significant and direct impact.
Briefly recall the primary function of each organ: Heart (pump), Lungs (gas exchange), Liver (metabolism/synthesis), and Kidneys (filtration/excretion).
Compare these functions in the context of fluid regulation. The kidneys are the only organs that actively and selectively filter the blood to remove or retain precise amounts of water and electrolytes.
Conclude that while other organs have secondary or passive roles, the kidneys are the primary regulators, making it the correct answer.

Concept Tested & Keywords

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