In the activation order of the extrinsic coagulation pathway, which sequence is correct?

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Multiple Choice

In the activation order of the extrinsic coagulation pathway, which sequence is correct?

The key idea is how the extrinsic coagulation pathway starts. Tissue factor (factor III) is exposed at the site of injury and immediately binds circulating factor VII to form the tissue-factor–factor VIIa complex. This complex then drives the downstream steps, most notably activating factor X to Xa and pushing the cascade toward thrombin formation. Because the initiating trigger is tissue factor and it activates factor VII to VIIa in the same complex, the correct activation order is tissue factor first, then factor VII. The other options place factor VII before tissue factor or skip the essential initial TF–FVIIa activation step, which doesn’t fit how the extrinsic pathway begins.

The key idea is how the extrinsic coagulation pathway starts. Tissue factor (factor III) is exposed at the site of injury and immediately binds circulating factor VII to form the tissue-factor–factor VIIa complex. This complex then drives the downstream steps, most notably activating factor X to Xa and pushing the cascade toward thrombin formation. Because the initiating trigger is tissue factor and it activates factor VII to VIIa in the same complex, the correct activation order is tissue factor first, then factor VII. The other options place factor VII before tissue factor or skip the essential initial TF–FVIIa activation step, which doesn’t fit how the extrinsic pathway begins.

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