Learning Objective

Understand the anatomical course, major branches, and clinical significance of the aorta.

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The aorta is the largest artery in the body, measuring approximately 2.5 cm (1 inch) in diameter at its origin. It receives blood from the left ventricle and distributes oxygenated blood to the entire body via the systemic circulation.

The aorta is divided into four main parts:

• Ascending aorta
• Aortic arch
• Thoracic (descending) aorta
• Abdominal aorta

It terminates at the level of the L4 vertebra, where it bifurcates into the right and left common iliac arteries.  In this article, we will examine the anatomy of the aorta – its anatomical course, branches, and clinical correlations.

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Ascending Aorta

The ascending aorta arises from the aortic orifice of the left ventricle and ascends to become the aortic arch. It is approximately 5 cm (2 inches) long and enclosed within the pericardial sac, ascending with the pulmonary trunk.

Branches

At its root, the ascending aorta contains two aortic sinuses – small dilatations located just above the cusps of the aortic valve:

• Right aortic sinus → right coronary artery
• Left aortic sinus → left coronary artery

These vessels supply the myocardium and are the only branches of the ascending aorta.

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Aortic Arch

The aortic arch is a continuation of the ascending aorta. It arches superiorly, posteriorly, and to the left before descending to become the thoracic aorta at the level of T4. It is connected to the pulmonary trunk by the ligamentum arteriosum.

Branches

• Brachiocephalic trunk → divides into right common carotid and right subclavian arteries
• Left common carotid artery → supplies the left side of the head and neck
• Left subclavian artery → supplies the left upper limb

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Clinical Relevance: Coarctation of the Aorta

Coarctation of the aorta refers to a congenital narrowing, usually near the ligamentum arteriosum. It increases left ventricular afterload and causes left ventricular hypertrophy. Upper body perfusion is preserved, but lower body perfusion is reduced, leading to radio-femoral delay.

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Thoracic Aorta

The thoracic aorta descends from T4 to T12, initially left of the vertebral column, moving midline as it goes. Major branches include:

• Bronchial arteries
• Mediastinal arteries
• Oesophageal arteries
• Pericardial arteries
• Superior phrenic arteries
• Intercostal and subcostal arteries

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Abdominal Aorta

The abdominal aorta begins at T12 and ends at L4, bifurcating into the common iliac arteries. Key branches include:

• Inferior phrenic arteries
• Coeliac artery (celiac trunk)
• Superior mesenteric artery
• Middle suprarenal arteries
• Renal arteries
• Gonadal arteries
• Inferior mesenteric artery
• Median sacral artery
• Lumbar arteries

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Clinical Relevance: Aortic Aneurysm

An aortic aneurysm is defined as a dilation >1.5× normal diameter. Most common in the infrarenal abdominal aorta. Patients may present with a pulsatile abdominal mass, abdominal/back pain, or may be asymptomatic. Thoracic aneurysms can compress mediastinal structures, e.g., left recurrent laryngeal nerve → hoarseness. Large aneurysms risk rupture.

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