24.22: The Aorta
The aorta is the largest artery in the human body. It originates from the left ventricle of the heart and extends down to the abdomen, where it splits into two smaller arteries. Structurally, it can be divided into four main parts: the ascending aorta, the aortic arch, the thoracic aorta, and the abdominal aorta.
The average diameter of the aorta is approximately 2-3 cm, but the size can vary depending on the section of the aorta and the individual's age, sex, and body size. The aorta is located slightly to the left of the midline in the thoracic and abdominal cavities.
As the primary artery stemming from the heart, the aorta is responsible for supplying blood to nearly all body tissues. The base of the aorta houses the aortic semilunar valve, which halts the regurgitation of blood into the left ventricle during heart relaxation periods. The ascending aorta, traveling vertically for roughly 5 cm, ends at the sternal angle. After its upward journey, the aorta curves elegantly to the left, forming what is known as the aortic arch. This arch then proceeds downwards, ending at the intervertebral disc between the fourth and fifth thoracic vertebrae. The descending aorta, closely following the vertebrae bodies, moves through the diaphragm via the aortic hiatus. The aorta above this hiatus is referred to as the thoracic aorta, while below it, it becomes the abdominal aorta. The abdominal aorta concludes its course by splitting into two common iliac arteries at the fourth lumbar vertebra.
The aorta is clinically significant. Conditions such as aortic aneurysms, aortic dissection, and aortic stenosis primarily involve the aorta and can be life-threatening if not treated promptly. Understanding the anatomy of the aorta can aid in the timely diagnosis and treatment of these conditions.
