# Great Vessels and Aortic Arch Variants > Great vessels and aortic arch variants for MBBS Anatomy: branch order, bovine arch, dysphagia lusoria, vascular rings and coarctation. - Canonical URL: https://prepelephant.com/topics/mbbs/anatomy/great-vessels-and-aortic-arch-variants - Exam / course: MBBS · Subject: Anatomy - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Great Vessels and Aortic Arch Variants", PrepElephant, https://prepelephant.com/topics/mbbs/anatomy/great-vessels-and-aortic-arch-variants ## Direct answer Three branches leave the aortic arch from right to left — the brachiocephalic trunk, left common carotid and left subclavian — the arch rising behind the manubrium to end at the sternal angle's plane (T4), the left recurrent laryngeal nerve hooking beneath it at the ligamentum arteriosum. Variants are common and questioned: a bovine arch (brachiocephalic trunk and left carotid sharing an origin) is the commonest; an aberrant right subclavian arises last and passes behind the oesophagus, causing dysphagia lusoria; right-sided and double arches form vascular rings. The pulmonary trunk carries the ligamentum arteriosum, the fetal ductus, whose patency after birth produces the continuous machinery murmur. ## What you must remember - **Standard arch branches:** brachiocephalic trunk (dividing into right subclavian and right common carotid), left common carotid, left subclavian — in that right-to-left order, behind the manubrium; the left recurrent laryngeal nerve loops under the arch at the ligamentum and is the voice's ambassador in the mediastinum. - **Surface relations:** the ascending aorta begins behind the left third costal cartilage; the superior vena cava runs to its right into the right atrium. - **Bovine arch:** the commonest variant — left common carotid arising from the brachiocephalic trunk or sharing its origin; found in up to a fifth of people, usually silent but a caveat in carotid and aortic imaging. - **Aberrant right subclavian:** arises as the arch's last branch and crosses behind the oesophagus — dysphagia lusoria, occasionally with a Kommerell diverticulum at its origin; it also makes a right subclavian steal possible when it arises from the descending aorta with retrograde vertebral flow. - **Rings and right arches:** a double aortic arch encircles the trachea and oesophagus — infant stridor with dysphagia; a right-sided arch with aberrant left subclavian forms a ring and associates with tetralogy of Fallot; an interrupted arch presents with neonatal shock when the ductus closes. - **Ductus arteriosus:** the fetal link from pulmonary trunk to aorta closes functionally in the first days of life; patency gives a continuous machinery murmur below the left clavicle, with wide pulse pressure — closure in preterm neonates is achieved with ibuprofen or indomethacin, a pharmacology question rooted here. - **Coarctation of the aorta:** the adult (postductal) type narrows the isthmus beyond the left subclavian — upper-limb hypertension with weak, delayed femoral pulses (radio-femoral delay), and collateral flow through the internal mammary and intercostal arteries notching the ribs' lower borders. ## An infant who cannot breathe and swallow A six-month-old has stridor worsened by feeding and a barium swallow showing posterior oesophageal and anterior tracheal indentations: a vascular ring, most completely a double aortic arch encircling both tubes. The embryonic double arch system explains the family: persistence of both fourth arches gives the double arch; regression of the wrong segments gives the right arch with aberrant left subclavian, or the aberrant right subclavian — in which an adult complains of obstructed swallowing because the arch's last branch crosses behind the gullet. In the adult clinic, a young hypertensive has arm blood pressure 60 millimetres higher than leg, delayed femoral pulses and rib notching: coarctation of the isthmus, the very segment the ligamentum tethers, his collaterals engraving the ribs' inferior margins for years. ## How the exam frames the arch The first question is branch order, and the trap is left-sided: candidates recite from the left and reverse it. The second is the variant menagerie, and a complete answer names bovine arch as the commonest and silent, aberrant subclavian as dysphagia lusoria's cause, and the double arch as the complete ring. The third pairs classic signs: the machinery murmur below the left clavicle of a patent ductus, and coarctation's radio-femoral delay — the notching sits on the lower borders of the third to eighth ribs, where dilated collateral intercostals groove the bone, a detail examiners quote because it is anatomical. ## Frequently asked questions ### What is the normal order of branches of the aortic arch? From right to left: the brachiocephalic trunk, the left common carotid artery and the left subclavian artery. The left recurrent laryngeal nerve hooks beneath the arch at the ligamentum arteriosum. ### What is a bovine arch? The commonest arch variant, in which the left common carotid artery arises from the brachiocephalic trunk or shares a common origin with it. Usually asymptomatic, it matters during arch surgery, carotid access and imaging interpretation. ### What causes dysphagia lusoria? An aberrant right subclavian artery arising as the arch's last branch and crossing behind the oesophagus, compressing it. A Kommerell diverticulum at its origin may enlarge and worsen the compression. ### Why does coarctation of the aorta cause rib notching? Collateral flow is rerouted through the internal mammary and intercostal arteries around the narrowing; the enlarged intercostal arteries groove the lower borders of the third to eighth ribs. Upper-limb hypertension with radio-femoral delay accompanies it. ### What murmur suggests a patent ductus arteriosus? A continuous machinery murmur maximal below the left clavicle, with a wide pulse pressure. Prostaglandin keeps the fetal ductus open; ibuprofen or indomethacin closes it in preterm neonates.