Anatomy of the Heart
To understand heart disease it is important to have an understanding of the heart, its anatomy, the circulation of blood through the heart's four chambers, and the electrical system that keeps our hearts in rhythm.
For a guided tour of the heart and how it works, please click here.
Anatomy of the Aorta
The aorta is the largest vessel in the body. It transports oxygenated blood from the left ventricle of the heart to every organ. The aorta starts in the heart with the aortic valve; immediately adjacent is the aortic root, followed by the ascending aorta, the transverse aorta (the aortic arch), the descending aorta, and the thoracoabdominal aorta. The aorta ends in the abdomen after bifurcation (to divide or fork into two branches) of the abdominal aorta in the two common iliac arteries.
The size of the aorta is directly proportionate to the patient’s height and weight. Its diameter may range from 3cm (more than an inch) to 1.2cm (half an inch). It is typically the largest in the aortic root and smallest in the abdominal aorta.
The aorta is divided in seven sections:
The aorta starts with the aortic valve just below the first branches of the aorta, the coronary arteries. It is the most important valve of the heart and the most commonly replaced heart valve.
The aortic valve usually has three leaflets and commissures (tricuspid) but may also have two leaflets and commissures (bicuspid aortic valve). The patient with bicuspid aortic valve have a much higher chance to develop aneurysms and dissection (splitting or separating of tissues) of the aortic root and the ascending aorta.
The aortic root is the segment above the aortic valve and below the sinotubular junction. The left and right coronary arteries - supplying the heart with oxygenated blood – arise here from the sinuses of Valsalva. Aortic root is typically aneurysmal in many patients with connective tissue disorder.
The ascending aorta is the segment between the sinotubular junction and the largest aortic branch vessel; the innominate (brachiocephalic) artery. This is the only portion of the aorta that does not give any branch vessels. The ascending aorta is the most anterior (toward the front of the body) portion of the aorta. Therefore, the most common symptom from the ascending aorta and the aortic root is chest pain. This pain may be confused with chest pain associated with ischemic heart disease (coronary artery disease).
The aortic arch (transverse aorta) is a short segment where branch vessels to the head and arms start. It has typically three branches: First, the innominate (brachiocephalic) artery supplies right arm and right portion of head and brain with oxygenated blood. Next, the left carotid artery carries blood to the left head and brain. The last branch vessel from the aortic arch is usually the left subclavian artery supplying the left arm with blood. There are many anomalies of the aortic arch such as the bovine arch, where there are only two branch vessels off the aortic arch. The operations involving the aortic arch usually require the body to be cooled down using the heart-lung machine. This technique is called hypothermic circulatory arrest. Alternatives are complex hybrid operations that usually do not require heart-lung-machine.
Descending thoracic aorta
The descending thoracic aorta starts with the last branch vessel off the aortic arch and ends at the first branch in the abdominal aorta; the celiac artery. The descending thoracic aorta is the most posterior (toward the back of the body) portion of the aorta. Therefore, the most common symptom from the descending thoracic aorta is back pain, and it may be confused with back pain associated with back muscles, joints and nerve pain. The descending thoracic aorta has many branches that supply a portion of the spinal cord (the out-pouching of brain within the spinal column). Therefore, any intervention involving this portion of the aorta has the risk of spinal cord ischemic injury.
The abdominal aorta branches to the intestine and the kidneys and divides into left and right common iliac arteries. The branch vessels of the abdominal aorta include the celiac artery, the superior mesenteric artery, the left and right renal arteries, and the inferior mesenteric artery.
The thoracoabdominal aorta is the segment starting past the last branch of the aortic arch and ends with the abdominal aortic bifurcation into left and right common iliac artery.
Microscopic Anatomy of the Aorta
The aortic wall is made up of three layers:
- Inner layer of the intima (far left)
- Middle layer of the media (center)
- Outer layer of the adventitia that includes vessels (vasovasorum) supplying the aortic wall with oxygenated blood