The aorta, which is about 1 inch (2.5 centimeters) in diameter, is the largest artery of the body. It receives oxygen-rich blood from the left ventricle of the heart and distributes it to all of the body except the lungs (which receive blood from the right ventricle). Just after the aorta leaves the heart, smaller arteries that carry blood to the head and arms branch off. The aorta then arches down, with additional smaller arteries branching off along its route from the left ventricle to the lower abdomen at the top of the hipbone (pelvis). At this point, the aorta divides into the two iliac arteries, which supply blood to the legs.
Disorders of the aorta include
Aneurysms: Bulges in weak areas of the walls of the aorta
Dissection: Separation of the layers of the wall of the aorta
These disorders can be immediately fatal, but they usually take years to develop.
Aneurysms also can develop in other arteries of the trunk, arms, and legs (called peripheral arteries Aneurysms of Arteries in the Arms, Legs, and Heart An aneurysm is a bulge (dilation) in the wall of an artery. (See also Aortic Branch Aneurysms and Brain Aneurysms.) Aneurysms may occur in any artery. Aneurysms are most common in the aorta... read more ), such as the arteries at the back of the knee (popliteal arteries) and the main arteries of the thighs (femoral arteries). The arteries supplying the head (carotid arteries), the arteries supplying the brain (cerebral arteries), and the arteries supplying the heart muscle (coronary arteries) may also develop aneurysms.
A ruptured aneurysm in the brain may cause subarachnoid hemorrhage Subarachnoid Hemorrhage (SAH) A subarachnoid hemorrhage is bleeding into the space (subarachnoid space) between the inner layer (pia mater) and middle layer (arachnoid mater) of the tissues covering the brain (meninges)... read more 
.
Aortic Aneurysms
The pressure of blood inside the artery forces any weak areas in the artery's wall to balloon outward.
If untreated, an aneurysm may rupture, resulting in pain and internal bleeding serious enough to cause shock and sometimes death.
Location
Aneurysms can develop anywhere along the aorta. Three fourths of aortic aneurysms develop in the part of the aorta that passes through the abdomen (abdominal aorta Abdominal Aortic Aneurysms Abdominal aortic aneurysms are bulges (dilations) in the wall of the aorta in the part that passes through the abdomen (abdominal aorta). Abdominal aortic aneurysms typically slowly expand and... read more 
), and the rest develop in the part that passes through the chest (thoracic aorta Thoracic Aortic Aneurysms Thoracic aortic aneurysms are bulges (dilations) in the wall of the aorta in the part that passes through the chest (thorax). Thoracic aortic aneurysms may not cause symptoms, or they may cause... read more 
).
In older people, aneurysms are most likely to occur in areas where arteries branch Aortic Branch Aneurysms Aortic branch aneurysms are bulges (dilations) in the wall of the major arteries that come directly off of the aorta. (See also Overview of Aortic Aneurysms and Aortic Dissection.) The aorta... read more (for example, where the abdominal aorta branches into the iliac arteries) or in areas of stress (for example, in the popliteal artery).
There are different types of aneurysms. Some may be round (saccular) and others tubelike (fusiform). Most are fusiform.
Where Do Aortic Aneurysms Occur?
Aneurysms can develop anywhere along the aorta. Most develop in the abdominal aorta. The rest develop in the thoracic aorta, most commonly in the ascending aorta.  |
Causes
The most common cause of aortic aneurysms is
Less common causes include
Injuries to the aorta, most often due to a motor vehicle crash
In older people, almost all aneurysms occur in people with atherosclerosis. High blood pressure High Blood Pressure High blood pressure (hypertension) is persistently high pressure in the arteries. Often no cause for high blood pressure can be identified, but sometimes it occurs as a result of an underlying... read more 
, which is common among older people, and cigarette smoking increase the risk of an aneurysm. In people with Marfan syndrome Marfan Syndrome Marfan syndrome is a rare hereditary disorder of connective tissue, resulting in abnormalities of the eyes, bones, heart, blood vessels, lungs, and central nervous system. This syndrome is caused... read more 
, an aneurysm is most likely to develop in the first part of the aorta, where it emerges from the heart (the ascending aorta).
Complications
Consequences depend on the size of the rupture. A large rupture may be rapidly fatal, and a small one (sometimes termed a leak) may cause warning symptoms that allow people to seek medical care.
A blood clot (thrombus) often develops in the aneurysm because blood flow inside the aneurysm is sluggish. The clot may extend along the entire wall of the aneurysm. A blood clot may break loose (becoming an embolus), travel through the bloodstream, and block arteries. Aneurysms in the popliteal arteries are more likely to produce emboli than aneurysms in other arteries. Occasionally, calcium is gradually deposited in the wall of an aneurysm, making it easier to see on x-rays.
Aortic Dissection
Aortic dissection Aortic Dissection An aortic dissection is an often fatal disorder in which the inner layer (lining) of the aortic wall tears and separates from the middle layer of the aortic wall. Most aortic dissections occur... read more occurs when the inner lining of the aorta separates (tears) from the middle layer of the aorta, allowing blood to push between these layers, separating (dissecting) the middle layer of the wall from the still-intact outer layer. As a result, a new, false channel forms in the wall of the aorta. More than 90% of people who have an aortic dissection experience pain—typically sudden, excruciating pain, often described as tearing or ripping. As the dissection advances further along the aorta, it can close off the points at which one or more arteries branch off from the aorta, blocking blood flow. The consequences vary depending on which arteries are blocked.
