Anterior basal segment of left lung

The anterior basal segment of the left lung (S8) is one of the bronchopulmonary segments of the left lower lobe. It is defined as a discrete, anatomically and functionally independent unit of lung parenchyma that is ventilated by its own segmental bronchus (B8), supplied by its own segmental pulmonary artery (A8), and drained by a corresponding segmental pulmonary vein.

Anatomical boundaries and relationships:

• The anterior basal segment is situated on the anterior and inferior surface of the left lower lobe, resting against the diaphragm inferiorly and facing the anterior chest wall.

• It is bordered superiorly by the superior segment (S6), medially by the medial basal segment (S7) which is often diminutive on the left due to the cardiac silhouette laterally by the lateral basal segment (S9), and posteriorly by the posterior basal segment (S10).

• On the left side, the medial basal segment (S7) is frequently small or supplied as a subsegmental branch off the left A8 segment, reflecting the reduced space caused by the heart.

Bronchovascular anatomy:

• The segmental bronchus B8 arises from the left basal trunk after the takeoff of the superior segmental bronchus (B6). The left basal segmental bronchi most commonly divide in a bifurcation pattern (~75% of cases) or a trifurcation pattern (~18%).

• The segmental artery A8 accompanies B8 and lies peripherally relative to the bronchus (typically anterior). The segmental arteries may be single, duplicate, or even triplicate, with anatomic variation from the dominant pattern occurring in up to 20% of cases.

• The segmental vein drains into the left inferior pulmonary vein and generally lies central (posterior or medial) to the bronchus.