The left main bronchus carries air from the trachea to the left lung. It is about twice as long as the right (around 5 cm), narrower and more horizontal. It passes beneath the arch of the aorta and in front of the oesophagus and descending aorta before dividing into upper and lower lobe bronchi.
| Location | From the carina laterally and downwards to the hilum of the left lung, below the aortic arch and in front of the oesophagus and descending thoracic aorta. |
|---|---|
| Parts |
|
| Nerve Supply | Pulmonary plexus; Vagus nerve (parasympathetic, bronchoconstriction and mucus secretion); Sympathetic fibres from T2-T5 ganglia (bronchodilation) |
| Blood Supply | Bronchial arteries |
| Venous drainage |
|
| Lymphatic drainage |
|
Conducts air to and from the two lobes of the left lung.
Its longer course and position under the aortic arch make it more prone to external compression, for example by an aortic aneurysm, enlarged left atrium or lymph nodes. Left-sided double-lumen tubes are commonly used for one-lung ventilation in thoracic surgery because its length gives more room for the bronchial cuff.
Pressure on the bronchus from an enlarged heart chamber, aortic aneurysm or nodes. It can cause wheeze, collapse of part of the lung or infection.
Cancer arising in the bronchial lining. Central tumours may block the airway and cause collapse of the lung beyond.
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