Lingula of left lung

The lingula of the left lung is an anatomical subdivision of the left upper lobe that consists of two segments: the superior lingular segment (S4) and the inferior lingular segment (S5). The term "lingula" means "little tongue" in Latin, reflecting its tongue-like projection from the anterior-inferior portion of the left upper lobe.

Anatomically, the lingula is separated from the anterior segment (S3) of the left upper lobe by the lower branch of the draining vein of the anterior segment (V3b), which runs horizontally between these two regions. In some individuals (8-18% anatomically, though only 1.6% visible on routine chest X-rays), a left minor fissure may separate the lingula from the anterior segment, analogous to the oblique fissure of right lung (right minor) fissure that separates the right middle lobe from the right upper lobe.

The lingula has its own distinct bronchial and vascular supply. The lingular division bronchus branches from the left upper lobe bronchus and typically bifurcates into superior (B4) and inferior (B5) segmental bronchi in approximately 96.5% of individuals. The lingular segments are supplied by lingular arteries (which may arise from various locations along the pulmonary artery) and drained by lingular veins.

Clinically, the lingula is considered the left-sided anatomical counterpart to the right middle lobe, though it is technically part of the left upper lobe rather than a separate lobe. This distinction is important for surgical planning, as lingular segmentectomy can be performed for focal disease such as bronchiectasis or early-stage lung cancer.