The main artery in the body is the aorta, the largest blood vessel in the human cardiovascular system. It carries oxygen-rich blood from the left side of the heart and distributes it to every organ and tissue through a network of smaller branches. At rest, roughly 5 to 6 liters of blood pass through the aorta every minute, a volume that can increase sixfold during intense exercise.
Where the Aorta Sits and How It’s Shaped
The aorta begins at the top of the heart, rises upward, curves into a hook shape, then descends through the chest and abdomen before splitting into two smaller arteries that supply the legs. This entire path is divided into distinct segments, each with its own job.
The ascending aorta is the first stretch, rising from the heart to roughly the level of the upper chest. From there, the vessel curves backward to form the aortic arch, a U-shaped bend that gives off the major arteries feeding your brain, neck, and arms. After the arch, the descending aorta travels down behind the heart through the chest cavity. Once it passes through the diaphragm, it becomes the abdominal aorta, which supplies blood to the digestive organs, kidneys, and lower body before dividing at the pelvis.
In a healthy adult, the ascending aorta measures about 2.1 to 4.3 centimeters in diameter. Men tend to have a slightly wider aorta than women, averaging around 3.3 cm compared to about 3.0 cm. The vessel narrows as it descends, with the abdominal section being the smallest portion.
How the Aorta Handles Blood Pressure
Unlike rigid pipes, the aorta is elastic. Its wall is built from three layers. The innermost layer is a thin lining of cells that keeps blood flowing smoothly. The middle layer is the thickest, packed with elastic fibers, smooth muscle, and collagen arranged in concentric sheets. The outer layer is a protective coat of connective tissue. This layered design lets the aorta stretch when the heart pumps and then snap back between beats, smoothing out the pulses of pressure into steadier flow for the rest of the body.
This elasticity also means that blood pressure inside the aorta is slightly different from what you measure at your arm. Systolic pressure recorded at the upper arm typically reads about 20 mmHg higher than pressure measured directly inside the aorta, because pressure waves amplify as they travel into narrower, stiffer peripheral arteries. Your arm cuff reading is still clinically useful, but the aorta itself experiences a somewhat gentler force.
Major Branches of the Aorta
The aorta is the trunk of the arterial tree, and its branches reach every region of the body. The most critical branching happens at the aortic arch, where three large arteries split off:
- Brachiocephalic artery: the first and largest branch, which quickly divides to supply the right side of the head and the right arm.
- Left common carotid artery: carries blood to the left side of the brain and head.
- Left subclavian artery: feeds the left arm and also sends a branch up toward the brain through the back of the neck.
Just above the heart, two smaller but vital branches, the coronary arteries, split off from the very beginning of the aorta to supply the heart muscle itself. Farther down, the abdominal aorta gives off arteries to the stomach, liver, intestines, kidneys, and spinal cord before dividing into the two iliac arteries that serve the pelvis and legs.
What Can Go Wrong
Because the aorta handles such enormous volume and pressure, problems with it tend to be serious. The two most important conditions are aneurysms and dissections.
Aortic Aneurysm
An aneurysm is a bulge in the aortic wall where the vessel has weakened and stretched. An abdominal aortic aneurysm is formally diagnosed when the abdominal aorta reaches 3 centimeters or more in diameter, roughly 50% wider than normal. Most aneurysms grow slowly over years and produce no symptoms at all until they become large enough to risk rupture, which is a life-threatening emergency. Risk factors include smoking, high blood pressure, age over 65, male sex, and a family history of aneurysms.
Because aneurysms are so often silent, screening with a simple abdominal ultrasound can catch them early. The U.S. Preventive Services Task Force recommends a one-time screening ultrasound for men aged 65 to 75 who have ever smoked (defined as 100 or more cigarettes in a lifetime). Men in that age range who have never smoked may still benefit from selective screening. For women who have never smoked and have no family history, routine screening is not recommended.
Aortic Dissection
A dissection occurs when the inner lining of the aorta tears, allowing blood to force its way between the wall layers. This creates a false channel that can block blood flow to organs or cause the vessel to rupture. The sudden onset of severe, tearing chest or back pain is the hallmark symptom.
Dissections are classified by location. A Type A dissection involves the ascending aorta near the heart and almost always requires emergency surgery. A Type B dissection starts beyond the arch in the descending aorta and can sometimes be managed with blood pressure control and close monitoring, though severe cases also need intervention. Chronic high blood pressure is the single biggest risk factor for dissection.
Keeping the Aorta Healthy
The same habits that protect your heart protect your aorta. Keeping blood pressure in a healthy range is the most important step, since sustained high pressure accelerates wear on the elastic fibers in the aortic wall. Not smoking matters enormously: smoking damages the vessel wall directly and is the strongest modifiable risk factor for abdominal aneurysms. Regular physical activity, maintaining a healthy weight, and managing cholesterol all reduce the stress and inflammation that weaken arterial walls over time.
If you have a family history of aortic disease, particularly a first-degree relative who had an aneurysm or dissection, that information is worth sharing with your doctor. Some connective tissue conditions that run in families can predispose the aorta to problems at a younger age, and earlier imaging may be appropriate.