Factor XIa

**Definition:** Activated form of factor XI. In the intrinsic pathway, Factor XI is activated to XIa by factor XIIa in the presence of cofactor HMWK; (HIGH MOLECULAR WEIGHT KININOGEN). Factor XIa then activates factor IX to factor IXa in the presence of calcium.

**Tree numbers:** - D08.811.277.656.300.760.320 - D08.811.277.656.959.350.320 - D12.776.124.125.425.320 - D23.119.425.320

**Synonyms:** - Factor XI, Activated - Blood Coagulation Factor XI, Activated - Contact Activation Product - Coagulation Factor XIa - Factor 11A - Activated Factor XI - Factor Eleven A