Definition

Noun 1. A coagulation factor: "Factor III" is the common name for thromboplastin, an enzyme-like protein substance. It is not a circulating factor in the blood but is released from damaged tissues and blood platelets (cell fragments). Its primary function is to initiate the extrinsic pathway of blood coagulation by converting the inactive enzyme prothrombin into the active enzyme thrombin, which is essential for forming a blood clot.

Usage Examples

• Noun:
  • Tissue damage releases factor III, which is a crucial first step in the clotting cascade.
  • The laboratory test measures the time it takes for a clot to form after factor III is added to the plasma sample.
  • Also known as thromboplastin, factor III is not deficient in hemophilia.

Advanced Usage

• Clinical Context: In medical diagnostics, "factor III" is often discussed in contrast to other coagulation factors (e.g., factor VIII, factor IX). Its activity is assessed in tests like the Prothrombin Time (PT), which evaluates the extrinsic pathway of coagulation it initiates.
• "Tissue factor": This is a more modern and precise synonym for factor III, emphasizing its cellular origin.

Variants and Related Words

• Thromboplastin (n): The direct biochemical name for factor III.
• Tissue factor (n): A contemporary term for factor III, highlighting its source from subendothelial cells and leukocytes.
• Coagulation factor (n): The general category to which factor III belongs.

Synonyms

• Thromboplastin
• Tissue factor
• Tissue thromboplastin

Related Phrases

• Extrinsic pathway: The specific sequence of clotting reactions initiated by factor III/tissue factor.
• Coagulation cascade: The entire series of stepwise reactions leading to blood clotting, in which factor III plays an initial role.

Noun

1. an enzyme liberated from blood platelets that converts prothrombin into thrombin as blood starts to clot