The principle of plasma protein responsible for exerting colloidal osmotic pressure is

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2022

Applied Physiology

Easy

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2022

Explanation

Albumin is the most abundant protein in the plasma, making up about 60% of total plasma proteins.
Due to its high concentration, it is the primary determinant of colloid osmotic pressure (oncotic pressure), contributing to about 80% of the total effect.
This pressure is essential for holding water within the blood vessels, counteracting the hydrostatic pressure that pushes fluid out.
A significant drop in albumin levels leads to fluid shifting into the interstitial tissues, causing generalized edema.

Option A: Haemoglobin is a protein found inside red blood cells, not freely circulating in the plasma. Therefore, it does not contribute to the colloid osmotic pressure of the plasma.
Option B: C-reactive protein (CRP) is an acute-phase reactant protein. Its levels rise significantly during inflammation and infection, but it is not involved in the regulation of osmotic pressure.
Option D: Haptoglobin's main function is to bind to free hemoglobin released from damaged red blood cells (hemolysis). This prevents the loss of iron and protects the kidneys, but it has a negligible effect on colloid osmotic pressure.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Role of plasma proteins in maintaining colloid osmotic pressure as background academic context rather than a clinical decision trigger.
Low albumin levels (hypoalbuminemia) cause a decrease in colloid osmotic pressure, leading to fluid shifting from blood vessels into interstitial tissues, resulting in generalized edema. Nurses must assess for this in at-risk patients by checking for swelling in the limbs, face, and abdomen (ascites).
Common causes of hypoalbuminemia include liver disease (impaired synthesis), nephrotic syndrome (urinary loss), severe burns (plasma loss), and malnutrition (inadequate protein intake).
What if? A patient has severe liver cirrhosis. The liver's ability to produce albumin is severely impaired. This would lead to a drastic drop in colloid osmotic pressure, causing significant fluid accumulation in the abdomen (ascites) and peripheral edema, which are hallmark signs a nurse would monitor and manage.

How to Approach the Question

First, identify the key concepts in the question: 'plasma protein' and 'colloidal osmotic pressure'.
This is a factual recall question. Your goal is to remember the primary functions of major plasma proteins.
Consider each option. Ask yourself: Is this a plasma protein? If so, what is its main function?
Eliminate Haemoglobin first, as it is not a plasma protein; it's contained within red blood cells.
Recall that albumin is the most abundant plasma protein, which makes it the most likely candidate for exerting the main osmotic force.
Confirm your choice by remembering that C-reactive protein is for inflammation and haptoglobin is for binding free hemoglobin, neither of which relates to overall osmotic pressure.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 1 pp. 168-170, 169-171