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Anatomy · Heart & blood vessels

Superior vena cava

Drains everything above the diaphragm, bar the heart and lungs

Thorax · systemic veins

A short, wide, valveless vein, about 7 cm long, formed behind the lower border of the first right costal cartilage by the union of the right and left brachiocephalic veins. It carries deoxygenated blood from the head, neck, upper limbs and thoracic wall down into the right atrium, receiving the azygos vein on the way.

How to spot them

  • ▸Vertical tube on the right side of the ascending aorta, just to the right of the mediastinum
  • ▸Formed by two brachiocephalic veins meeting behind the first right costal cartilage
  • ▸The azygos vein arches over the root of the right lung to join its back just before it enters the pericardium
  • ▸Opens into the top of the right atrium at the level of the third costal cartilage

What to know

Formed by the union of the two brachiocephalic veins behind the first right costal cartilage

Superior vena cava.

A valveless vein about 7 cm long that returns blood from the head, neck and arms to the right atrium

Superior vena cava — it has no valves.

Just before it pierces the pericardium, the azygos vein arches over the right lung root to join it

Superior vena cava receives the azygos vein.

Its opening into the right atrium lies in the wall near the sinoatrial node

Superior vena cava.

Blockage of this vessel by a lung tumour causes facial swelling, distended neck veins and arm oedema

Superior vena cava obstruction (SVC syndrome).

The tip of a central venous catheter is ideally positioned at its junction with the right atrium

Superior vena cava — the cavoatrial junction.

Lies to the right of the ascending aorta; the right phrenic nerve runs alongside it on the mediastinal pleura

Superior vena cava — with the right phrenic nerve.

Key ideas

  • Its lower half is enclosed by the fibrous pericardium, with serous pericardium covering its front and sides.
  • Collateral routes if it is blocked: azygos system, internal thoracic veins, lateral thoracic veins, all dilating to bypass the obstruction.

Quick-fire facts

  • •About 7 cm long and about 2 cm in diameter.
  • •No valves, unlike many other veins.
  • •Formed by the right and left brachiocephalic veins, themselves formed by internal jugular and subclavian veins.
  • •Receives the azygos vein posteriorly just before entering the pericardium.
  • •Enters the right atrium at the level of the right third costal cartilage.
  • •The left brachiocephalic vein is longer than the right because it must cross the midline, passing in front of the great arteries.
  • •Superior vena cava syndrome most often results from lung cancer or lymphoma compressing it.
  • •Persistent left SVC is a normal variant in around 0.3–0.5% of people, draining via the coronary sinus.

Drill it — 7 cards

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Sources