This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
Lines of zahn are found in 
Select and explain. 
A. Thrombus, B. Infract tissue, C. Postmoem clot, D. All
A: Thrombus
Answer: A: Thrombus 
Explanation: ref Robbins 9/e p125 Thrombi can have grossly (and microscopically) apparent laminations called lines of Zahn; these represent pale platelet and fibrin layers alternating with darker red cell-rich layers. Such lines are significant in that they are only found in thrombi that form in flowing blood; their presence can there- fore usually distinguish antemoem thrombosis from the bland nonlaminated clots that form in the postmoem state. Although thrombi formed in the "low-flow" venous system superficially resemble postmoem clots, careful evaluation generally reveals ill-defined laminations.