Left main bronchus

Function

The left main bronchus is longer (5 cm) and more horizontal, angling beneath the aortic arch to reach the left lung, because the heart and arch lie to the left.

It divides into upper and lower lobar bronchi supplying eight to ten segments (some fused compared with the right); the left upper lobe's bronchi include the lingula's branches, the homologue of the right middle lobe.

Blood supply

Left bronchial arteries (usually two) from the aorta.

Nerve supply

Left vagal and sympathetic pulmonary plexuses.

Clinical relevance

Left lung cancer with hoarseness

Tumours in the left hilum compress the recurrent laryngeal nerve looping under the aortic arch — often a sign that the tumour is unresectable.

Related conditions

• Asthma
• Bronchiectasis