In initiating hemostasis, what typically activates platelets?Multiple choice question.low oxygen concentrationsreticulocyte activating factorexposed collagen

Answer

In the process of hemostasis, platelets are typically activated by exposed collagen. When vascular injury occurs, the underlying collagen in the blood vessel wall becomes exposed to the bloodstream, which is not normally in contact with circulating platelets. This exposure triggers the adhesion of platelets to the collagen through specific receptors, such as glycoprotein VI (GPVI).

Once bound, platelets become activated and undergo a series of changes, including shape change, degranulation, and aggregation. Other factors like thromboxane A2 and ADP are also released, which further enhance platelet activation and recruitment to the site of injury.

The other options, such as low oxygen concentrations and reticulocyte activating factor, are not directly involved in the activation of platelets during the hemostatic process. Thus, the correct answer is exposed collagen.