Embolus

: emboli; from the Greek ἔμβολος "wedge", "plug") is an unattached mass that travels through the bloodstream and is capable of creating blockages.

A related term is embolism, which describes the phenomenon of an embolus lodging in a vessel and creating a blockage.

[citation needed] In contrast to emboli, which can cause occlusion at sites distant from their points of origin, there are also non-traveling blockages that develop locally from vascular trauma and inflammation or other epithelial pathology, such as atheromata and thrombi.

Other more-common causes include the puncture of the subclavian vein by accident or during operation where there is negative pressure.

Air is then sucked into the veins by the negative pressure caused by thoracic expansion during the inhalation phase of respiration.

Gas embolism is a common concern for deep-sea divers because the gases in human blood (usually nitrogen and helium) can be easily dissolved at higher amounts during the descent into deep sea.

However, when the diver ascends to the normal atmospheric pressure, the gases become insoluble, causing the formation of small bubbles in the blood.

[11] Rudolf Virchow, the German physician and "father of pathology", is generally credited with the first explanation of the relationship between thrombi, emboli, and embolisms.

He coined the terms embolism (initially called "Embolia") and thrombosis while proposing a hypothesis for the pathophysiology of pulmonary thromboembolism.

[5][12] In his work, he described the consequences of thrombosis and the factors leading thereto, a concept which today is known as Virchow's Triad.