Ascending Aorta

The ascending aorta is the initial segment of the aorta, emerging from the left ventricle of the heart. It functions as the primary arterial outflow tract, carrying oxygenated blood from the heart into the systemic circulation. It gives rise to the coronary arteries that supply the heart itself and transitions superiorly into the aortic arch. The ascending aorta is entirely contained within the pericardial sac and lies in the middle mediastinum.

Origin and Course

The ascending aorta begins at the level of the aortic valve within the left ventricle, approximately at the level of the third left intercostal space, posterior to the sternum. It ascends obliquely upward, forward, and to the right, approximately 5 to 6 cm in length, before transitioning into the aortic arch at the level of the sternal angle (around T4 vertebral level).

Parts of the Ascending Aorta

Aortic Root: The segment of the aorta at the base, attached to the aortic valve; includes the aortic sinuses and coronary artery origins.
Aortic Sinuses: Also called the sinuses of Valsalva, these are three bulges in the wall of the aorta just above each cusp of the aortic valve. The right and left coronary arteries arise from the right and left sinuses, respectively. The third, posterior sinus does not give rise to a coronary artery.
Ascending Aorta Proper: The tubular portion that extends from the sinotubular junction up to the origin of the brachiocephalic artery.

Branches

Right Coronary Artery

Arises from the right aortic sinus and supplies the right atrium, most of the right ventricle, and portions of the left ventricle and septum.

Left Coronary Artery

Arises from the left aortic sinus and supplies the left atrium, most of the left ventricle, and the anterior part of the interventricular septum.

These coronary arteries are the only branches of the ascending aorta and provide the sole arterial blood supply to the myocardium.

Anatomical Relations

Sternum and left pleura
Right auricle and pulmonary trunk (partially anterior)

Posterior

Left atrium
Right pulmonary artery

Right

Superior vena cava
Right atrium

Left

Pulmonary trunk
Left auricle

Histological Structure

The wall of the ascending aorta is composed of three layers:

Tunica intima: Endothelium and subendothelial connective tissue
Tunica media: Thick layer of elastic fibers and smooth muscle cells, providing the elasticity needed to handle the high pressure generated during systole
Tunica adventitia: Connective tissue containing vasa vasorum and nerves supplying the aortic wall

Function

The ascending aorta plays a vital role in:

Delivering oxygenated blood to the entire body through systemic circulation
Supplying the heart itself via the coronary arteries

During ventricular systole, the aortic valve opens, allowing blood to flow into the ascending aorta. During diastole, elastic recoil in the aortic wall helps maintain blood pressure and perfusion, especially to coronary vessels.

Clinical Notes (Minimal)

Aneurysm: Aneurysmal dilation of the ascending aorta can occur due to connective tissue disorders (e.g., Marfan syndrome) or hypertension. It poses a risk of dissection or rupture.
Aortic Dissection: The ascending aorta is the most common site for Type A aortic dissections, a life-threatening emergency.

Topographic Summary

Origin: Aortic valve of the left ventricle
Termination: Continues as the aortic arch at the level of the sternal angle (T4)
Length: Approximately 5–6 cm
Contained in: Middle mediastinum, within the pericardial sac
Branches: Right and Left Coronary Arteries