Plasma protein responsible for oncotic pressure maintenance is?

ESIC Nursing Officer 2016 (Shift -2)

Applied Physiology

Easy

Appeared in: ESIC Nursing Officer 2016 (Shift -2)

Explanation

Albumin is the most abundant protein in the plasma, making up about 80% of the total colloid osmotic pressure.
Its primary function is to maintain oncotic pressure, which regulates fluid balance between the blood vessels and tissues.
Albumin's large size prevents it from easily passing through capillary walls, creating a pressure gradient that holds fluid within the vasculature.
A decrease in albumin levels directly leads to a drop in oncotic pressure, causing fluid to shift into the interstitial space and result in edema.

Option A: Globulins are primarily involved in the immune response (as immunoglobulins or antibodies) and transporting lipids and hormones. While they contribute to oncotic pressure, it is not their main function.
Option B: Prothrombin (Factor II) is a zymogen (inactive enzyme precursor) involved in the blood clotting cascade. It has no primary role in maintaining oncotic pressure.
Option C: Thrombin is an active enzyme that converts fibrinogen into fibrin to form a blood clot. Its function is specific to hemostasis, not oncotic pressure.

Visual 1: Diagram - Starling's forces at the capillary. This visual should illustrate how hydrostatic pressure pushes fluid out of the capillary and how colloid osmotic pressure (generated by albumin) pulls fluid back in, demonstrating the balance of fluid exchange.
Visual 2: Infographic - Functions of Plasma Proteins. A chart showing the main plasma proteins (Albumin, Globulins, Fibrinogen) and their respective percentages and primary functions (oncotic pressure, immunity, clotting).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain The role of plasma proteins in maintaining oncotic pressure as background academic context rather than a clinical decision trigger.
Nurses frequently monitor for signs of edema (e.g., pitting edema in the legs, ascites) in patients with conditions that cause low albumin, such as liver failure, malnutrition, or nephrotic syndrome.
Understanding the role of albumin is critical for administering albumin infusions and monitoring the patient's response, which includes assessing for a reduction in edema and improved fluid balance.
Patient education often involves explaining dietary protein needs to support albumin synthesis, especially in chronic conditions like cirrhosis.

How to Approach the Question

First, identify the key terms in the question: 'plasma protein' and 'oncotic pressure'.
This is a factual recall question. Access your knowledge about the major types of plasma proteins.
Consider the primary function of each option: Globulin (immunity), Prothrombin/Thrombin (clotting), and Albumin (oncotic pressure, transport).
Recall that oncotic pressure (or colloid osmotic pressure) is the force that holds fluid inside blood vessels.
Match the function to the protein. Albumin is the most abundant plasma protein and its main role is to maintain this pressure.
Therefore, select Albumin as the correct answer.

Concept Tested & Keywords

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