What is the definition or description of: aortic dissection?

The aorta tears: The aorta is made up layers. When blood gets in between the layers through a tear it causes the aorta to dissect the dissection flap closes and obstructs flow.

Blood under lining: The aorta is composed of 3 layers in its wall: inner, middle, &outer. A dissection occurs when there is a crack in the inner wall permitting blood from inside the aorta to move thru the crack and travel in the space between inner and outer walls. The space is tight so forcing thru the space causes pain, usually in the back. If blood breaks thru the outer wall, massive bleeding can occur.

Internal,tear: The dissection is a tear of the inner lining of the aortic three layer wall the flap may obstruct branches of the aorta and create a whole series of symptoms and complications. Medical and surgical treatments exist depending on the exact situation.