Cysticmedialnecrosis. The aorta is a living organ. Has 3 layers. Intima, media, adventitia. The aortic wall is nourished by the vasa vasorum. Arteriosclerosis creates cholesterol plaque, the vasa vasorum occlude, the media slowly dies and becomes replaced by collagenous tissue, pressure and Collagenase activity weaken wall and it dilates excessively, if not repaired claims 17, 000 americans/yr.70%infrarenal.
Unknown . There are factors thought to be associated with the development of an aortic aneurysm such as genetic problems with an enzyme called elastase, other types of collagen disorders, and possibly hypertension. It is difficult, if not impossible, to detect the specific cause for most individual patients.