Which factor is activated when a blood sample contacts the glass of a test tube?

1. The intrinsic pathway is also called the contact activation pathway. 2. It is most often initiated when factor XII, the Hageman factor, meets foreign material. 3. Glass is such a foreign material, so a sample standing in a glass tube clots along this route. 4. Inside the body, factor XII is typically activated by negatively charged molecules instead. 5. Factor III is the extrinsic starter, released by damaged tissue, so it is the wrong pathway. 6. Factors VIII and IX act later within the intrinsic sequence rather than initiating it, which makes them the plausible near misses. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 18 "The Cardiovascular System: Blood", section 18.5 Hemostasis_