Final answer:
Venous thrombosis occurs when blood clots form in veins, often due to prolonged periods of inactivity, certain medical conditions, or genetic factors. It can lead to serious complications such as deep vein thrombosis and pulmonary embolism when clots travel to the lungs.
Step-by-step explanation:
Venous thrombosis can occur in situations where there is damage to the endothelial lining of blood vessels, leading to activation of the clotting mechanism. This is often triggered by venous stasis, where blood remains stationary for prolonged periods, as in long airplane flights or with chronic conditions like heart failure. Other contributing factors include thrombophilia (a tendency to form blood clots, which may be genetic or acquired), and behaviors or conditions such as prolonged sitting, lupus, immune reactions to heparin, polycythemia vera, sickle cell disease, pregnancy, and obesity. Deep vein thrombosis (DVT) is a serious instance of venous thrombosis, where a blood clot forms in a deep vein, most commonly in the leg. If a clot dislodges, it can lead to a potentially lethal complication called pulmonary embolism (PE), where the clot obstructs blood flow to the lungs.