Left lung — inferior lobe

Function

The left lower lobe has four segments — the superior segment plus three basal segments (the anterior and medial basal segments are usually fused).

Like its right counterpart it receives the lung's largest perfusion share and bears the diaphragm's dome impression; its posterior basal segment is the mirror site of dependent lung disease.

Blood supply

Left pulmonary artery's lower branches.

Nerve supply

Left pulmonary plexus.

Clinical relevance

Left lower lobe collapse

The left lower lobe collapses behind the heart as a 'sail sign' behind the cardiac silhouette — easy to miss.

Related conditions

• Pneumonia
• Idiopathic pulmonary fibrosis
• Pleural effusion