Definition and Characteristics of Bronchopulmonary Segments
Definition
A bronchopulmonary segment is a well-defined, pyramidal-shaped, anatomical, functional, and surgical unit of the lung that is aerated by a tertiary (segmental) bronchus and supplied by a segmental branch of the pulmonary artery.
There are 10 bronchopulmonary segments in each lung — 10 on the right side and 10 on the left side — giving a total of 20.
Shape and Orientation
- Shape: Pyramidal (wedge-shaped)
- Apex: directed towards the hilum (root) of the lung
- Base: directed towards the pleural surface (costal or mediastinal)
- Surrounded by connective tissue that separates it from adjacent segments
Characteristic Features
- It is a subdivision of a lobe of the lung (not the lung as a whole)
- Pyramidal in shape — apex towards hilum, base towards surface
- Surrounded by connective tissue (intersegmental connective tissue septa)
- Aerated by its own tertiary (segmental) bronchus
- Each segment has its own segmental artery — a branch of the pulmonary artery running centrally alongside the bronchus
- Each segment has its own lymphatic drainage and autonomic nerve supply
- Segmental veins (tributaries of pulmonary veins) run in the intersegmental planes — they are shared between adjacent segments and do not belong to a single segment
Why Not a Bronchovascular Segment?
A bronchopulmonary segment is not a bronchovascular segment because it does not have its own vein. The pulmonary venous tributaries run in the connective tissue planes between segments (intersegmental planes) and drain more than one segment.
This intersegmental position of the veins is surgically important: during segmental resection, the surgeon works along the segmental veins to identify and isolate the planes between segments.
Functional and Surgical Significance
- Disease in one segment may remain limited to that segment (e.g., tuberculosis, bronchiectasis, benign neoplasm)
- Each segment can be resected independently with minimal disturbance to surrounding healthy lung tissue (segmental resection)
- This is the anatomical basis for conservative lung surgery