Platelets are a source of?

HPSSC Staff Nurse - 2021

Applied Physiology

Easy

Appeared in: HPSSC Staff Nurse - 2021

Explanation

Platelets are a key source of platelet thromboplastin, also known as Platelet Factor 3 (PF3).
PF3 is a phospholipid that is exposed on the surface of activated platelets.
It provides a crucial binding site for the assembly of clotting factors (tenase and prothrombinase complexes) in the intrinsic pathway of the coagulation cascade.
This activation cascade is essential for converting prothrombin into thrombin, which then converts fibrinogen to fibrin to form a stable clot.

Option A: Fibrinogen (Factor I) is a soluble plasma protein that is primarily synthesized in the liver. It is the precursor to fibrin but is not sourced from platelets.
Option B: Calcium ions (Factor IV) are essential cofactors for several enzymatic reactions in the coagulation cascade. However, the body's source of calcium is dietary intake, and it circulates freely in the plasma or is stored in bones.
Option D: Haemoglobin is the iron-containing protein responsible for oxygen transport. It is found exclusively within red blood cells (erythrocytes) and has no function in the coagulation process.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Role of platelets in hemostasis and coagulation as background academic context rather than a clinical decision trigger.
Understanding the role of platelets is vital for nurses when managing patients with bleeding disorders (e.g., thrombocytopenia) or those at risk of thrombosis.
Monitoring platelet counts is a standard nursing intervention for patients receiving chemotherapy, heparin, or those with certain infections that can affect platelet levels.
What if? If a patient has a severely low platelet count (thrombocytopenia), their ability to form a primary platelet plug and initiate the intrinsic clotting cascade is significantly impaired. This places them at high risk for spontaneous bleeding (e.g., petechiae, ecchymosis) and prolonged bleeding from injuries, requiring bleeding precautions.

How to Approach the Question

This is a factual recall question about hematology.
First, identify the core concept: the function of platelets in blood clotting (hemostasis).
Recall the substances involved in the coagulation cascade and their origins.
Evaluate each option: Fibrinogen is a plasma protein from the liver. Calcium is a mineral from the diet. Haemoglobin is in red blood cells.
Recognize that thromboplastin is a general term for a substance that initiates clotting. Platelets release a specific type (Platelet Factor 3) essential for the intrinsic pathway.
By eliminating the other options based on their known sources, thromboplastin remains as the correct answer related to platelet function in coagulation.

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