Final answer:
The extrinsic pathway is one of the two pathways involved in blood clotting and is activated by trauma or damage to the surrounding tissues.
Step-by-step explanation:
The extrinsic pathway is one of the two pathways involved in blood clotting. It is activated by trauma or damage to the surrounding tissues. The key proteins involved in this pathway are factor III (thromboplastin), calcium ions (Ca²+), and factor VII (proconvertin). These proteins form an enzyme complex that activates factor X, leading to the common pathway of blood clotting.