The aorta is the main blood vessel in the human body. As blood is pumped from the heart, it passes across the aortic valve, and then through the aorta, where it is then distributed through a system of smaller arteries. As the aorta travels through the body, each portion has a different name based on its location and each section supplies different organ systems or areas of the body. The aorta first leaves the heart and brings blood towards the head as the ascending aorta. As the aorta turns towards the left side of the body, it gives off branches to the upper body and the brain as the aortic arch. The aorta next travels down the chest, where it is called the descending aorta. The descending aorta continues through the abdomen as the abdominal aorta, where it supplies the abdominal organs before dividing to provide arteries for each leg (the iliac arteries).
The wall of the aorta is made up of three layers, the thin adventitia on the outside, the media, which is thicker and more elastic, and the delicate intima on the inside. The elastic nature of the vessel wall helps the aorta respond to the high pressures produced as blood is ejected from the heart.
Structure of the Aorta
Aortic root - The root is the beginning of the aorta. Starting from the aortic valve (annulus) and becoming slightly wider in diameter (sinuses of Valsalva), it gives rise to two coronary arteries and ends at the beginning of the ascending aorta (sinotubular junction). The two coronary arteries are responsible for carrying oxygen-rich blood to the heart muscle itself.
Ascending aorta - This segment extends upward from the aortic root to the point where the innominate artery branches off the aorta, and the aorta begins to form an arch. It is within the heart sack (pericardium) by itself and no arteries branch from it. There is little support from surrounding tissue and it must face the entire cardiac output volume (minus the coronary arteries), making the ascending segment the most vulnerable part of the aorta.
Aortic arch - The arch represents the curved portion at the top of the aorta. The innominate, left common carotid, and left subclavian arteries, which supply blood to the head and upper body, branch from the arch. It is outside the pericardial sack and generally has better support from surrounding structures.
Descending aorta - This section begins just beyond the arch as the aorta bends down into the body. The descending aorta ends at the diaphragm. It contains the intercostal arteries that feed the spinal cord. The beginning portion of the descending aorta is vulnerable to injury (intimal tear) during deceleration conditions.
Abdominal aorta - The abdominal aorta is the largest artery in the body and the most common section for aortic aneurysms. It begins at the diaphragm and ends at the "guts" where it divides into the two common iliac arteries (right and left). The abdominal aorta is critical as it supplies blood to the abdominal and pelvic organs, as well as the legs.