The cross-sectional view of a blood vessel showing the progression of a blood clot. The normal vessel anatomy includes red blood cells (RBCs), platelets, and fibrin. The formation of an initial clot occurs when fibrin and platelets ensnare red blood cells. The clot then enlarges as more RBCs are ensnared by the fibrin web. A portion of the clot can then break off and join the bloodstream as an embolus.
