Lung bronchopulmonary segments are anatomical and functional regions of lung parenchyma formed from subdivisions of each lobe. They are characterised by:
- having a relatively constant spatial arrangement:
- between segments in a lobe
- relative to the hilum and surface of each lung; each segment is approximately pyramidal with its apex at the hilum and base occupying a consistent position on the surface of the lung
- between individuals in a population
- a supply from a discrete tertiary branch of the bronchial tree, the segmental bronchi
- in keeping with the number of segmental bronchi, there are usually ten bronchopulmonary segments on each side
- acting as separate functional units within the lung:
- each segment is supplied solely by the following structures with little collateral connection between segments:
- segmental bronchus entering centrally at the apex of each segment
- a segmental branch or branches of the pulmonary artery; tends to be centrally sited within each segment
- a segmental branch or branches of the bronchial artery; centrally located within each segment
- additionally, along the planes between segments, there are the main tributaries of the pulmonary veins and lymphatics which are produced by the convergence of smaller vessels within the parenchyma of adjacent segments
- this has two advantages:
- pathology may be confined to individual segments
- the segments are easy to identify and remove at operation
The further division of segmental bronchi within each segment produces secondary then primary lobules; vascular, lymphatic and nerve supplies ramify in a similar manner.