An embolus is a particle that moves about in our blood vessels, either in the veins or arteries. Most emboli are composed of clotted blood cells. A blood clot is called a thrombus and a moving blood clot is called a thromboembolus.
As an embolus moves through the body's blood vessels, it's likely to come to a passage it can't fit through. It lodges there, backing up blood behind it. The cells that normally get their blood supply via this passage are starved of oxygen (ischemia) and die. This condition is called an embolism.
Types of embolism
There are several types of embolism:
- pulmonary embolism: An embolus, usually formed in the leg (sometimes known as a deep vein thrombosis or DVT), lodges in one of the arteries of the lungs. Many emboli are broken down by the body and go away by themselves; however, serious pulmonary embolism may cause death.
- brain embolism: If a blood clot travels to the brain, this causes an ischemic stroke or TIA (transient ischemic attack).
- retinal embolism: Small clots that wouldn't block a major artery can block the smaller blood vessels feeding the retina at the back of the eye. The result is usually sudden blindness in one eye.
- septic embolism: This occurs when particles created by infection in the body reach the bloodstream and block blood vessels.
- amniotic embolism: Not all emboli are made of clotted blood. In pregnancy, the womb is filled with amniotic fluid, which protects the fetus. Amniotic fluid can embolize and reach the mother's lungs, causing pulmonary amniotic embolism.
- air embolism: Scuba divers who rise to the surface too rapidly can generate air embolism, bubbles in the blood that can block arterial blood flow.
- fat embolism: If fat or bone marrow particles are introduced into the blood circulation, they may block blood vessels the way a blood clot or air bubble can.