What causes arterial thrombosis?

Arterial thrombosis is primarily caused by the formation of a thrombus, or blood clot, within an artery, which typically occurs at sites of vascular injury or damage, such as when atherosclerotic plaques rupture. When a plaque in the arterial wall ruptures, the underlying materials become exposed to the bloodstream, leading to the activation of platelets. This activation causes the platelets to aggregate, forming a clot at the site of injury. This is a critical process, as it is intended to prevent further bleeding; however, in the case of arterial thrombosis, this excessive aggregation can lead to obstruction of blood flow, resulting in serious conditions like heart attacks or strokes.

The factors related to the other choices do not directly explain the primary cause of arterial thrombosis. For instance, while deficiency of platelets can lead to bleeding disorders, it would not cause thrombosis. Excessive fibrinolysis refers to the breakdown of clots rather than their formation and would therefore be counterproductive to arterial thrombosis. Similarly, a decreased level of hemoglobin pertains to anemia and its effects on blood oxygen transport, rather than the specific mechanism of thrombus formation within arteries.