An embolism occurs when foreign material travels through the bloodstream and becomes lodged in a blood vessel. Embolisms typically become lodged in the large or medium-sized arteries located anywhere in the body, especially in the neck, lungs, brain, intestine, legs, arms or kidneys.

The particle causing the blockage (called an embolus) could be one of many substances that may travel through the bloodstream, including:

An embolus travels through the branches of an artery or vein until it becomes stuck. Once lodged, it obstructs oxygen-rich blood from nourishing whatever parts of the body lie beyond it. As a result, the tissues on the other side of the blockage begin to die from lack of oxygen. If oxygen depletion continues long enough – sometimes only a matter of minutes – oxygen–starved tissues and organs will stop functioning and become permanently damaged.