Aortic arch

At a glance

English

Aortic arch

Latin (TA2)

Arcus aortae

System

Artery

Region

Trunk

Side

Single, on the midline

About the aortic arch

The aortic arch, also called the transverse arch, links the ascending aorta to the descending thoracic aorta. It begins behind the right side of the sternum at the level of the second sternocostal joint and runs upwards, backwards and to the left, first in front of the trachea and then along its left side. It ends beside the T4 vertebral body on the left, where it turns down as the descending aorta. Its highest point sits roughly 2.5 cm beneath the top of the manubrium.

Because it travels both upwards and backwards, the arch has two curves: one convex upwards and one convex forwards and to the left. From its upper surface spring three large branches. The brachiocephalic trunk comes first, the largest, behind the manubrium and in front of and to the right of the others; the left common carotid follows, and finally the left subclavian artery. These carry blood to the arms, neck and head. Variations are common: the brachiocephalic trunk and left common carotid often share an origin, and the left vertebral artery sometimes arises straight from the arch between the left carotid and subclavian.

The arch lies in the superior mediastinum. In front and to the left it is crossed by the left phrenic and left vagus nerves and by cardiac nerves, and covered by the left pleura and lung. Behind and to the right lie the trachea, oesophagus, thoracic duct and left recurrent laryngeal nerve, which hooks under the arch beside the ligamentum arteriosum. Below it are the pulmonary trunk bifurcation, the left main bronchus and the left recurrent nerve. The left brachiocephalic vein crosses above it. The wall contains baroreceptors that sense stretching and help adjust heart rate to blood pressure, sending signals mainly through the vagus.

Its central part develops from the left fourth pharyngeal arch artery. The final stretch, the isthmus, lies where the ligamentum arteriosum attaches; narrowing here is coarctation of the aorta, which reduces blood flow to the lower body. The isthmus is also where the aorta most often tears in sudden deceleration injuries. On a frontal chest X-ray the arch forms the aortic knob, and aneurysm of the arch can press on the trachea or the left recurrent laryngeal nerve, causing hoarseness.

Course and supply

Arises from

Continues from the ascending aorta behind the right half of the sternum at the level of the second sternocostal joint.

Ends in

Becomes the descending thoracic aorta alongside the left side of the T4 vertebral body.

Supplies

Carries blood from the heart towards the rest of the body and, through its three branches, supplies the head, neck and upper limbs; its baroreceptors help regulate blood pressure.