What characterizes an arterial thrombus in terms of structure?

An arterial thrombus is characterized by the presence of lines of Zahn, which are alternating layers of platelets and fibrin in the thrombus structure. These lines represent the organized nature of the thrombus as it forms in the bloodstream under conditions of flow. The white layers consist primarily of platelets and fibrin, while the red layers include red blood cells that become entrapped within the fibrin mesh.

The formation of lines of Zahn indicates that the thrombus developed in a well-oxygenated environment, which is typical in arteries where blood flow is more vigorous compared to venous thrombi. This layered appearance also signifies that there was a temporal sequence in the deposition of platelets and fibrin, distinguishing it from a thrombus that would lack this organization.

In contrast, other structures like those with a uniform structure would typically indicate a different pathology, such as a post-mortem clot, which lacks the same organization and cellular components. Therefore, the presence of lines of Zahn specifically highlights the flow dynamics and cellular composition distinctive to an arterial thrombus.