Lobe of lung

A lobe of the lung is a distinct anatomical compartment of the lung, separated from adjacent lobes by connective tissue boundaries called pulmonary fissures. The human lungs are divided into five lobes in total:

• Right lung: three lobes - the right upper lobe, right middle lobe, and right lower lobe, separated by the right oblique (major) fissure and the right horizontal (minor) fissure.

• Left lung: two lobes - the left upper lobe and left lower lobe, separated by the left oblique (major) fissure.

Each lobe is relatively independent in terms of anatomy and function, receiving its own lobar bronchus and lobar branches of the pulmonary artery and vein. This functional independence makes lobe-based analysis clinically important for lesion localization, surgical planning, and regional assessment of lung disease.

The fissures that define the lobes are not always complete. A systematic review found that anatomical variations in lung fissures and lobes occur in nearly 42% of individuals:

• The right horizontal fissure is complete in only about 54% of cases, while the right and left oblique fissures are complete in approximately 77% and 72%, respectively.

• Accessory fissures (creating additional subdivisions) are present in about 14% of lungs.