Bronchi
Name the Sequential Airways of the Conduction Zone
2. Findings and Diagnosis
The bronchogram shows the path of the inspired air from the trachea to mainstem bronchi, lobar bronchi , segmental bronchi to subsegmental bronchi. The next level is the bronchiole which is peripheral and barely visualised in the right lower lobe above the diaphragm
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Conduction Zone of the Airways
- The conduction zone is the portion of the airway that
- transports air but
- does not participate in gas exchange.
- Function: Warms, humidifies, and filters incoming air.
- Structures Included:
- Trachea
- Mainstem bronchi
- Lobar bronchi
- Segmental bronchi
- Subsegmental bronchi
- Bronchioles
- Terminal bronchioles (last part of the conduction zone)
- Ends at: The terminal bronchioles, where the respiratory zone begins.
The airway follows an asymmetric branching pattern, similar to a maple tree, with a strong central trunk and unevenly spaced branches.
Asymmetric Branching Pattern of the
Conduction Zone
Similar to the
Asymmetric Branching Pattern of the Airways
The classical branching pattern of many trees
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| Airway Structure | Description |
|---|---|
| Trachea | Central airway; bifurcates at the carina |
| Mainstem Bronchi | First division of trachea |
| – Right Mainstem Bronchus | Shorter, wider, more vertical |
| – Left Mainstem Bronchus | Longer, narrower, more oblique |
| Lobar Bronchi | Branches to each lung lobe |
| – Right Lobar Bronchi | Upper, Middle, Lower |
| – Left Lobar Bronchi | Upper, Lower |
| Segmental Bronchi | Branches supplying lung segments |
| Subsegmental Bronchi | Further division of segmental bronchi |
| Bronchioles | Smallest conducting airways, no cartilage |
| Terminal Bronchiole | Last conducting airway before gas exchange |
Visibility on Imaging
-
CXR (Chest X-ray):
- Visible: Trachea, mainstem bronchi, some lobar bronchi (if abnormal).
- Not visible: Smaller bronchi and bronchioles.
-
CT Scan:
- Visible: Trachea, mainstem bronchi, lobar bronchi, segmental bronchi, subsegmental bronchi.
- Limited visibility: Normal bronchioles (~0.5–2 mm) are generally not visible due to their small size, which is below the spatial resolution of conventional CT (~0.5–1 mm).
- Visible if abnormal: Bronchioles can be detected if thickened (e.g., due to inflammation or fibrosis), dilated (e.g., bronchiolectasis), or filled with mucus or fluid (e.g., tree-in-bud pattern).
Beyond the Conduction Zone
The Respiratory Zone
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