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The superior vena cava (SVC) returns deoxygenated blood from the head and neck, upper limbs, and thorax to the right atrium.
The aorta and pulmonary trunk are the two major arterial outflow tracts of the heart, both derived embryologically from a single truncus arteriosus.
These great vessels lie closely related at the root of the heart
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.Formed by the union of right and left brachiocephalic (innominate) veins behind the lower border of the first right costal cartilage, near the sternum.
Each brachiocephalic vein = internal jugular + subclavian vein
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.About 7 cm long.
Begins behind the lower border of the 1st right costal cartilage, pierces the pericardium opposite the 2nd, and opens into the right atrium behind the 3rd right costal cartilage.
No valves present
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.Anterior: Chest wall, internal thoracic vessels, right lung and pleura.
Posterior: Trachea, right vagus nerve, root of right lung.
Medial: Ascending aorta, brachiocephalic artery.
Lateral: Right phrenic nerve, right pleura and lung
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.Azygos vein (arches over right lung root).
Small mediastinal and pericardial veins.
Ascending Aorta
Arch of Aorta
Descending Thoracic Aorta
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.Origin: Upper end of left ventricle, enclosed in pericardium.
Length: ~ 5 cm.
Course: Upward, forward, to the right → becomes arch of aorta at upper border of 2nd right costal cartilage.
Relations:
Anterior: Sternum, right lung and pleura, RV infundibulum, pulmonary trunk, right auricle.
Posterior: Transverse pericardial sinus, LA, right pulmonary artery, right bronchus.
Right side: SVC, right atrium.
Left side: Pulmonary trunk (above), LA (below).
Branches:
Right coronary artery — from anterior aortic sinus.
Left coronary artery — from left posterior aortic sinus
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.Course: Upward, backward, then downward behind left bronchus to continue as descending aorta.
Branches (“ABC’S” Mnemonic):
A – Aortic arch
B – Brachiocephalic trunk
C – Left Common Carotid
S – Left Subclavian
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.Lies in posterior mediastinum; gives posterior intercostal, bronchial, oesophageal, pericardial, superior phrenic arteries.
Origin: From right ventricle.
Course: Ascends obliquely upward, backward, left; divides into right and left pulmonary arteries carrying deoxygenated blood to lungs.
Relations with Aorta (Triple Relationship):
At the heart base → pulmonary trunk lies anterior to ascending aorta.
At upper heart border → lies left of aorta.
Above that → right pulmonary artery lies posterior to ascending aorta
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.Development: Pulmonary trunk + ascending aorta both arise from truncus arteriosus.
Superior Vena Cava: Upper half from caudal part of right anterior cardinal vein.
Arch of Aorta: Left aortic sac + 4th aortic arch + left dorsal aorta.
Pulmonary Trunk: Derived from truncus arteriosus
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.SVC Obstruction above azygos opening: Venous return via azygos vein → dilated chest veins up to costal margin.
SVC Obstruction below azygos opening: Blood drains to IVC through thoraco-epigastric veins → veins dilated on chest and abdomen.
Mediastinal syndrome: Early signs = SVC obstruction (supraclavicular venous engorgement)
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.Patent Ductus Arteriosus (PDA): Persistent connection between left pulmonary artery and aortic arch → continuous “machinery murmur” at 2nd left intercostal space; treated surgically
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.SVC: Second largest vein of body.
Aorta: Largest elastic artery; transitions to muscular type in branches.
Pulmonary trunk: Arises from right ventricle; divides into two arteries carrying deoxygenated blood.
Aorta & Pulmonary trunk: Common origin – truncus arteriosus.
Triple relation: Pulmonary trunk (anterior) → left of aorta → right pulmonary artery posterior
The aorta is the great arterial trunk of the systemic circulation.
It carries oxygenated blood from the left ventricle to all parts of the body.
It is divided into three parts:
Ascending aorta
Arch of aorta
Descending thoracic aorta
Begins from the upper end of the left ventricle behind the left half of the sternum at the lower border of the 3rd costal cartilage.
About 5 cm long, enclosed within the pericardium.
It runs upward, forward, and to the right, ending at the upper border of the 2nd right costal cartilage to continue as the arch of aorta
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.At its root, the wall of the aorta shows three dilatations — the aortic sinuses:
Anterior sinus → gives rise to Right Coronary Artery
Left posterior sinus → gives rise to Left Coronary Artery
Right posterior sinus → no branch
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.Anterior: Sternum, right lung and pleura, infundibulum of right ventricle, pulmonary trunk, right auricle.
Posterior: Transverse sinus of pericardium, left atrium, right pulmonary artery, right bronchus.
Right side: Superior vena cava and right atrium.
Left side: Pulmonary trunk (above) and left atrium (below).
Right coronary artery from anterior aortic sinus.
Left coronary artery from left posterior aortic sinus.
Continuation of the ascending aorta; lies in superior mediastinum behind manubrium sterni.
Begins behind upper border of 2nd right sternocostal joint, arches upward, backward, and to the left over the root of left lung, ending at the lower border of 4th thoracic vertebra where it continues as descending thoracic aorta
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.Anterior and to the Left:
Four nerves (from before backward):
Left phrenic nerve
Lower cervical cardiac branch of left vagus
Superior cervical cardiac branch of left sympathetic chain
Left vagus nerve
Left superior intercostal vein
Left pleura and lung
Remains of thymus
Posterior and to the Right:
Trachea, deep cardiac plexus, tracheobronchial lymph nodes
Esophagus
Left recurrent laryngeal nerve
Thoracic duct
Vertebral column
Superior:
Branches of arch (brachiocephalic, left common carotid, left subclavian) — all crossed by left brachiocephalic vein.
Inferior:
Bifurcation of pulmonary trunk, left bronchus, ligamentum arteriosum, and superficial cardiac plexus.
Brachiocephalic artery → divides into right common carotid and right subclavian.
Left common carotid artery
Left subclavian artery
Mnemonic: “ABC’s of Aortic Arch”
A – Arch of aorta
B – Brachiocephalic trunk
C – Left Common carotid artery
S – Left Subclavian artery
Begins at lower border of T4 vertebra and ends at T12, where it passes through aortic opening of diaphragm to become the abdominal aorta
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.Anterior: Root of left lung, pericardium, esophagus.
Posterior: Vertebral column, hemiazygos veins.
Right side: Esophagus, thoracic duct, azygos vein.
Left side: Left pleura and lung.
Visceral:
Bronchial arteries (one right, two left)
Esophageal arteries
Pericardial branches
Parietal:
Posterior intercostal arteries (3rd–11th spaces)
Subcostal arteries
Superior phrenic arteries
Aortic Knuckle:
Seen on chest X-ray as a projection beyond the left mediastinal margin — more prominent in elderly individuals
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.Coarctation of Aorta:
Congenital narrowing opposite or just distal to the ductus arteriosus.
Causes rib notching due to enlarged intercostal arteries forming collateral circulation.
Ductus Arteriosus & Ligamentum Arteriosum:
In fetal life, ductus arteriosus connects left pulmonary artery to arch of aorta (distal to left subclavian).
After birth, it closes to form ligamentum arteriosum.
Patent Ductus Arteriosus (PDA): Persistence after birth → left-to-right shunt, continuous machinery murmur.
Aortic Arch Aneurysm:
Localized dilatation that can compress left recurrent laryngeal nerve → hoarseness, dyspnea, dysphagia (Mediastinal Syndrome)
The pulmonary trunk is a wide arterial vessel that carries deoxygenated blood from the right ventricle to the lungs.
Origin: From the summit of the infundibulum (conus arteriosus) of the right ventricle.
Length: About 5 cm; enclosed with the ascending aorta in a common sleeve of serous pericardium.
Position: Lies anterior to the ascending aorta at its origin and overlies it.
Course:
Runs upward, backward, and to the left.
Divides under the concavity of the aortic arch (at the sternal angle) into right and left pulmonary arteries.
Right Pulmonary Artery
Passes behind ascending aorta and superior vena cava, in front of esophagus.
Gives first branch to the upper lobe of right lung before entering the hilum.
Left Pulmonary Artery
Passes in front of descending thoracic aorta to reach the left lung hilum.
Connected to the inferior surface of the aortic arch by the ligamentum arteriosum, a remnant of ductus arteriosus.
Brachiocephalic Artery: From right aortic sac.
Right Subclavian Artery:
Proximal part → right 4th aortic arch.
Distal part → right 7th cervical intersegmental artery.
Left Subclavian Artery: From left 7th cervical intersegmental artery.
Common Carotid Artery: From third aortic arch and adjacent dorsal aorta.
External Carotid Artery: As a sprout from the third aortic arch.
Pulmonary Trunk: From truncus arteriosus.
Arch of Aorta: From left aortic sac + left 4th aortic arch + left dorsal aorta.
Relation to Recurrent Laryngeal Nerve:
Left side: Distal part of 6th aortic arch forms ligamentum arteriosum → left recurrent laryngeal nerve hooks around it in thorax.
Right side: Distal part disappears → right recurrent laryngeal nerve hooks around right subclavian artery in neck
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.Upper half (extrapericardial): From caudal part of right anterior cardinal vein.
Lower half (intrapericardial): From right common cardinal vein.
Coronary sinus: From left horn of sinus venosus, receiving great, middle, and small cardiac veins
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.Pulmonary trunk and ascending aorta develop from the truncus arteriosus (common embryonic origin).
They exhibit a triple relationship:
Close to heart → pulmonary trunk anterior to aorta.
At heart’s upper border → pulmonary trunk left of aorta.
Above → right pulmonary artery posterior to ascending aorta
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