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Anatomy · Heart & blood vessels

Pulmonary artery

Carries deoxygenated blood to the lungs

Thorax · pulmonary circulation

The pulmonary trunk leaves the right ventricle through the pulmonary valve and, after about 5 cm, divides beneath the aortic arch into the right and left pulmonary arteries, one to each lung. It is the main exception to the rule that arteries carry oxygenated blood: it carries the body's deoxygenated blood to the lungs to be reoxygenated.

How to spot them

  • ▸Emerges from the front of the heart at the top of the right ventricle, passing up and back
  • ▸Wraps round the front and left of the ascending aorta before dividing
  • ▸The right branch passes behind the ascending aorta and the superior vena cava
  • ▸A fibrous cord, the ligamentum arteriosum, joins the left branch to the aortic arch

What to know

An artery that carries deoxygenated blood, leaving the right ventricle

Pulmonary artery — the pulmonary trunk.

About 5 cm long, it divides below the aortic arch into a right and a left branch, one for each lung

Pulmonary artery — bifurcation of the pulmonary trunk.

Its right branch runs behind the ascending aorta and the superior vena cava to reach the lung

Pulmonary artery — right pulmonary artery.

A fibrous cord, the remnant of the foetal ductus arteriosus, joins it to the arch of the aorta

Pulmonary artery — the ligamentum arteriosum; the left recurrent laryngeal nerve hooks beneath it.

A low-pressure vessel: its mean pressure at rest is normally no more than about 20 mmHg

Pulmonary artery — mean pulmonary arterial pressure.

A clot travelling from the deep leg veins and lodging in this vessel or its branches is a classic cause of sudden breathlessness

Pulmonary artery — pulmonary embolism.

Guarded at its origin by a valve with three semilunar cusps, anterior, right and left

Pulmonary artery — the pulmonary valve at its base.

Key ideas

  • Arteries carry blood away from the heart; whether it is oxygenated or not depends on the circuit. The pulmonary artery is the classic example of deoxygenated blood in an artery.
  • Its wall is thinner and more distensible than the aorta's, matching the low-pressure pulmonary circuit.

Quick-fire facts

  • •The pulmonary trunk is about 5 cm long and about 3 cm in diameter.
  • •It bifurcates in the concavity of the aortic arch, in front of the left main bronchus.
  • •The pulmonary valve has three semilunar cusps: anterior, right and left.
  • •The ligamentum arteriosum connects the pulmonary trunk (left branch) to the aortic arch; it is the remnant of the foetal ductus arteriosus.
  • •Normal mean pulmonary arterial pressure is up to about 20 mmHg; pulmonary hypertension is defined by higher values.
  • •The pulmonary trunk and its branches lie on the anterior surface of the heart and hilum of the lungs.
  • •A Swan–Ganz (pulmonary artery) catheter is floated through the right heart into it to measure wedge pressure.
  • •In the foetus, most of the right ventricular output bypasses the lungs through the ductus arteriosus.

Drill it — 7 cards

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Sources