Provide the definitions/explanations for the following terms:
$(1)$ Thrombus
$(2)$ Embolus

(N/A) $(1)$ Thrombus: Fatty substances accumulate in the injured part of an artery and form a plaque. If this plaque remains attached to the arterial wall,it is called a thrombus.
$(2)$ Embolus: When a plaque formed on the wall of an artery breaks off from its original site and circulates through the bloodstream,it is referred to as an embolus.