Blood penetrates the intima and enters the media layer. As with all other arteries, the aorta is made up of three layers, the intima, the media, and the<unk> ventitia. The intima is in direct contact with the blood inside the vessel, and mainly consists of a layer of endothelial cells on a basement membrane; the media contains connective and muscle tissue, and the vessel is protected on the outside by the<unk> ventitia, comprising connective tissue. In an<unk> , blood penetrates the intima and enters the media layer. The high pressure rips the tissue of the media apart along the laminated plane splitting the inner two-thirds and the outer one-third of the media apart. This can propagate along the length of the aorta for a variable distance forward or backward.<unk> s that propagate towards the iliac bifurcation (with the flow of blood) are called anterograde<unk> s and those that propagate towards the aortic root (opposite of the flow of blood) are called retrograde<unk> s. The initial tear is usually within 100 mm of the aortic valve, so a retrograde<unk>  can easily compromise the pericardium leading to a hemopericardium. Anterograde<unk> s may propagate all the way to the iliac bifurcation of the aorta, rupture the aortic wall, or recanalize into the intravascular lumen leading to a double-barrel aorta. The double-barrel aorta relieves the pressure of blood flow and reduces the risk of rupture. Rupture leads to hemorrhaging into a body cavity, and prognosis depends on the area of rupture. Retroperitoneal and pericardial ruptures are both possible. Histopathological image of<unk> g aneurysm of the thoracic aorta in a patient without evidence of Marfan syndrome: The damaged aorta was surgically removed and replaced by artificial vessel, Victoria blue & HE stain. The initiating event in<unk>  is a tear in the intimal lining of the aorta. Due to the high pressures in the aorta, blood enters the media at the point of the tear. The force of the blood entering the media causes the tear to extend. It may extend proximally (closer to the heart) or distally (away from the heart) or both. The blood travels through the media, creating a false lumen (the true lumen is the normal conduit of blood in the aorta). Separating the false lumen from the true lumen is a layer of intimal tissue known as the intimal flap. The vast majority of<unk> s originate with an intimal tear in either the ascending aorta (65%), the aortic arch (10%), or just distal to the ligamentum arteriosum in the descending thoracic aorta (20%). As blood flows down the false lumen, it may cause secondary tears in the intima. Through these secondary tears, the blood can re-enter the true lumen. While it is not always clear why an intimal tear may occur, quite often it involves degeneration of the collagen and elastin that make up the media. This is known as cystic medial necrosis and is most commonly associated with Marfan syndrome and is also associated with Ehlers-Danlos syndrome. In about 13% of<unk> s, no evidence of an intimal tear is found. In these cases, the inciting event is thought to be an intramural hematoma (caused by bleeding within the media). Since no direct connection exists between the true lumen and the false lumen in these cases, diagnosing an<unk>  by aortography is difficult if the cause is an intramural hematoma. An<unk>  secondary to an intramural hematoma should be treated the same as one caused by an intimal tear.
Aortic dissection
Costochondritis
Aortic rupture
Tietze syndrome  Tietze syndrome  1
Acute aortic syndrome
Thoracic aortic aneurysm
Aortoenteric fistula
Myocardial rupture