Anatomy of the Secondary Lobule

Secondary lobule

- Basic anatomic unit of lung function
- Measures 1-2cm in size, contains 5-15 acini, is bounded by connective tissue septa
- Supplied by a small bronchiole (also called the terminal bronchiole, as it is the most distal extent of the conducting zone)
- The bronchiole is central in the secondary lobule
- The bronchiole is accompanied by a centrilobular artery
- Together, the bronchiole and centrilobular artery compose the bronchovascular bundle
- This bundle is surrounded by the central network of lymphatics
- The connective tissue septa bounding the secondary lobule contains the peripheral lymphatic network and the veins
Radiograph below demonstrates the central (within the secondary lobule) bronchovascular bundle (B - bronchiole, A - centrilobular artery) and the peripheral connective tissue septa (S) containing veins (V). Lymphatics (too small, not labeled) run both centrally and peripherally.


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