Histopathology of a pulmonary artery with<unk>  embolism (seen as multiple empty globular spaces on this H&E stain since its processing dissolves<unk> . There is a bone marrow fragment in the middle, and multiple single hematopoietic cells in the blood, being evidence of fracture as the source of the embolism. Once<unk>  emboli enter the blood circulation, they can lodge at various sites of the body, most commonly in the lungs (up to 75% of cases). However, it can also enter the brain, skin, eyes, kidneys, liver, and heart circulation, causing capillary damage, and subsequently cause organ damage in these areas. There are two theories that describe the formation of a<unk>  embolus: * Mechanical theory - Following trauma,<unk>  is released directly from the bone marrow into the circulation. This is because after trauma, an elevated pressure in the medullary cavity (central cavity of the bone where the bone marrow are stored) causes the release of<unk>  globules into the venous system supplying the bone. Since venous blood returns to the right heart and is pumped to the lungs for reoxygenation, the<unk>  globules often get lodged in the pulmonary circulation.<unk>  globules may also pass through lung circulation back into the left ventricle of the heart to be pumped throughout the body in the systemic circulation. They may also reach the systemic circulation through a patent foramen ovale (a hole communicating the right atrium directly to the left atrium of the heart). If<unk>  globules obstruct 80% of the lung capillary network, the resulting back pressure on the right heart increases workload and causes right heart dilatation through cor pulmonale, leading to acute right heart failure. * Biochemical theory - Following trauma, an inflammation causes bone marrow to liberate<unk> ty acids into the venous circulation. This is achieved through the increased activity of lipoprotein lipase which break down triglycerides into free<unk> ty acids. Both the release of<unk> ty acids and the inflammation causes damage to the capillary beds of the lungs and other organs, causing interstitial lung disease, chemical pneumonitis, and acute respiratory distress syndrome (ARDS). This theory can help to explain non-traumatic causes of<unk>  embolism.
Fat embolism syndrome
Pulmonary embolism
COACH syndrome
Pneumonia
Wooden chest syndrome
Acute chest syndrome
Inferior vena cava syndrome
Aspiration pneumonia