Blood clots are formed when there is damage to the lining of blood vessels, either an artery or vein. The damage may be obvious, such as a cut or laceration, or may not be visible to the naked eye. Blood also begin to coagulate if it stops moving, and stagnates, or diseases that cause blood to clot abnormally.
vein thrombosis Blood clots
Venous thrombosis occurs when a person is immobilized and muscles are not contracting to pump blood back to the heart. This stagnant blood begins to form small clots along the walls of the vein. This initial clot can gradually grow to partially or completely occlude or block the vein and prevent blood returning to the heart.
An analogy for this process is a slow moving river. Over time, weeds and algae start to accumulate along the banks of the river where the water flows more slowly. Gradually, as the weeds begin to grow, they begin to invade the middle of the river, as they can withstand the pressure of the water flow in the opposite direction.
Blood clots arterial thrombi
blood clots in an artery (arterial thrombosis) occur by a different mechanism. For those with atherosclerotic disease, plaque deposits form along the lining of the artery and grow, which causes the container to narrow. This disease process can cause:
peripheral arterial disease.
If a plate is broken, a blood clot may form at the site of the break and can partially or totally occlude blood flow at that point.
Common causes of blood clots (thrombi)
hardening of the arteries, high cholesterol
surgery that affects blood circulation
lesions of arteries
atrial fibrillation – a type of rapid, irregular heart rhythm