Embolus

An embolus (plural emboli; from the Greek ἔμβολος "wedge", "plug") is an unattached mass that travels through the bloodstream and is capable of clogging arterial capillary beds (create an arterial occlusion) at a site distant from its point of origin. There are a number of different types of emboli, including blood clots, cholesterol plaque or crystals, fat globules, gas bubbles, and foreign bodies.

By contrast there are non-traveling blockages that develop locally from vascular trauma or epithelial pathology and vascular inflammation — such as atheromata and thrombi. However, if a thrombus breaks loose from its genesis site it becomes a thrombo-embolus and if not broken down during transit, may cause embolism(s).

The term was coined in 1848 by Rudolf Virchow.

In thromboembolism, the thrombus (blood clot) from a blood vessel is completely or partially detached from the site of thrombosis (clot). The blood flow will then carry the embolus (via blood vessels) to various parts of the body where it can block the lumen (vessel cavity) and cause vessel obstruction or occlusion. The free-moving thrombus is called an embolus. A thrombus is always attached to the vessel wall and is never freely moving in the blood circulation. This is also the key difference for pathologists to determine the cause of a blood clot, either by thrombosis or by post-mortem blood clot. Vessel obstruction will then lead to different pathological issues such as blood stasis and ischemia. However, not only thromboembolism will cause the obstruction of blood flow in vessels, but also any kind of embolism is capable of causing the same problem.

Fat embolism usually occurs when endogenous (from sources within the organism) fat tissue escapes into the blood circulation. The usual cause of fat embolism is therefore the fracture of tubular bones (such as the femur), which will lead to the leakage of fat tissue within the bone marrow into ruptured vessels. There are also exogenous (from sources of external origin) causes such as intravenous injection of emulsions.

...
Wikipedia