It is the circulation of undissolved material known as embolus and its impaction in small arteries. Embolism occurs only in arteries, never in veins except in the portal veins.
Type of emboli:
1- Detached part of a thrombus:
Non-infected thrombotic emboli lead to infarction while infected ones lead to pyemia.
2- Tumor emboli: formed of malignant cells that produce secondary deposits in distant organs known as metastases.
3- Parasitic emboli: e.g. Bilharzial ova.
4- Air emboli: This occurs in cut wounds in the neck.
5- Fat emboli: in fracture of bone and in marked fatty change.
6- Atheromatous emboli.
7- Amniotic fluid emboli: fatal.