Bronchopulmonary Segments

1. Overview

Bronchopulmonary segments are anatomically and functionally distinct subdivisions of each lung lobe, each supplied by its own segmental (tertiary) bronchus and branch of the pulmonary artery. They are the smallest independent lung units that can be surgically resected without affecting adjacent segments. Typically, there are 10 segments in each lung, although the left lung may have fewer due to developmental variations and lobe fusion. These segments are essential in pulmonary anatomy, surgery, and radiology.

2. Location

Bronchopulmonary segments are located within the lobes of the lungs, arranged in a predictable, hierarchical fashion:

• Each lung is divided into lobes (3 on the right, 2 on the left).

• Each lobe is further divided into bronchopulmonary segments.

• Each segment is conical or pyramid-shaped, with its apex directed toward the hilum and base toward the pleura.

Typical Segment Distribution:

Right Lung (10 segments):

• Upper lobe: Apical, Posterior, Anterior

• Middle lobe: Lateral, Medial

• Lower lobe: Superior, Medial basal, Anterior basal, Lateral basal, Posterior basal

Left Lung (8–10 segments):

• Upper lobe: Apicoposterior, Anterior, Superior lingular, Inferior lingular

• Lower lobe: Superior, Anteromedial basal, Lateral basal, Posterior basal

3. Structure

Each bronchopulmonary segment has the following characteristics:

• Air supply: A segmental bronchus, a branch of the lobar bronchus.

• Blood supply: A segmental branch of the pulmonary artery (deoxygenated blood).

• Venous drainage: Intersegmental veins (between segments), draining into pulmonary veins.

• Lymphatic drainage: Travels centrally toward segmental and hilar lymph nodes.

• Shape: Roughly pyramidal, with apex pointing toward the lung hilum and base facing the pleura.

• Separation: Surrounded by thin connective tissue septa, helping isolate infections or tumors.

4. Function

The bronchopulmonary segments serve multiple critical respiratory functions:

• Compartmentalized ventilation: Independent bronchial supply allows localized airflow regulation.

• Gas exchange: Contain alveoli responsible for oxygen-carbon dioxide exchange with capillaries.

• Anatomical independence: Isolation of function allows one segment to be surgically removed without compromising adjacent segments.

5. Physiological Role(s)

Bronchopulmonary segments contribute to overall pulmonary efficiency and protection through:

• Functional autonomy: Localized control of airflow and perfusion via segmental bronchi and arteries.

• Defensive compartmentalization: Prevent spread of infections, tumors, or foreign bodies to other lung segments.

• Surgical utility: Facilitates segmentectomy or lobectomy in cases of localized disease, preserving more lung function than full-lobe removal.

• Radiological clarity: Segments are identifiable on imaging, aiding in targeted diagnosis and treatment planning.

6. Clinical Significance

Segmental Resection (Segmentectomy)

Surgeons can remove individual segments in cases of:

• Localized tumors

• Bronchiectasis

• Tuberculosis cavities

This is especially valuable when preserving maximum healthy lung tissue is necessary, such as in patients with limited pulmonary reserve.

Postural Drainage

Due to gravity-dependent drainage, certain body positions can be used to clear secretions from specific segments—useful in:

• Cystic fibrosis

• Chronic bronchitis

Example: Head-down positioning to drain posterior basal segments.

Bronchogenic Carcinoma

Primary lung cancers often arise within a single bronchopulmonary segment. Segmental knowledge helps with:

• Biopsy planning

• Staging and surgical margins

• Targeted resection

Pneumonia and Atelectasis

Infections and collapse often affect specific segments. Radiologists use segmental anatomy to interpret imaging and identify disease distribution.

Foreign Body Aspiration

Inhaled foreign bodies often lodge in specific segments due to anatomical angles—especially the right lower lobe superior or posterior basal segments due to the wider, more vertical right bronchus.