Final answer:
An obstruction in a blood vessel due to a blood clot or foreign substance that has traveled through the bloodstream and lodged in that vessel is referred to as an embolism. This can cause medical emergencies like heart attacks, strokes, or pulmonary embolisms.
Step-by-step explanation:
An obstruction in a blood vessel due to a blood clot or foreign substance that has traveled through the bloodstream and lodged in that vessel is referred to as an embolism. This can occur when a portion of a clot called an embolus breaks free from the vessel wall and enters the circulation. The embolus can then block a vessel critical to a major organ, leading to medical emergencies like heart attacks, strokes, or pulmonary embolisms.