Bronchi

The Bronchi arise from the Tracheal Bifurcation at the level of the Sternal angle and successively divide to form the bronchial tree. The main Bronchi runs in the mediastinum and divides into the Lobar Bronchi in the Hilum of Lung. Peripheral parts of the bronchial tree are located within the lung tissue itself. Cartilaginous rings are incomplete, dorsally opened C shaped rings in the primary bronchi 🡪 they become irregular plates and decrease towards the periphery of the bronchial tree.

Basic Bronchial Tree:

1. Trachea 🡪 right and left Primary Bronchi (for each lung)

2. Primary Bronchi 🡪 3 right and 2 left Secondary Bronchi (for each lobe) about 8-12mm in diameter

3. Secondary (lobar) Bronchi 🡪 10 right and 8 left Tertiary Bronchi (for each segment)

• Left Main Bronchus 🡪 Longer, Narrower, and more deviated from the tracheal axis.
• Right Main Bronchus 🡪 Shorter, wider, more vertical and almost continuous with the trachea

Branches and their subdivisions

Left Main Bronchus 🡪 Longer, Narrower, and more deviated from the tracheal axis.

1. Left Superior Lobar Bronchus
   • Apicoposterior Segmental Bronchus
   • Anterior segmental Bronchus
   • Superior Lingular Bronchus
   • Inferior Lingular Bronchus
2. Left Inferior Lobar Bronchus
   • Superior Segmental Bronchus
   • Medial Basal segmental Bronchus (missing in 90%)
   • Anterior Basal segmental Bronchus o Lateral Basal Segmental Bronchus
   • Posterior Basal Segmental Bronchus

Right Main Bronchus 🡪 Shorter, wider, more vertical and almost continuous with the trachea

1. Right superior lobar bronchus
   • Apical Segmental Bronchus
   • Posterior Segmental Bronchus
   • Anterior Segmental Bronchus
2. Right Middle lobar bronchus
   • Lateral Segmental Bronchus
   • Medial Segmental Bronchus
3. Right Inferior lobar bronchus
   • Superior (apical) Segmental Bronchus
   • Medial basal (cardiac) Segmental Bronchus
   • Anterior basal Segmental Bronchus
   • Lateral basal Segmental Bronchus
   • Posterior basal Segmental Bronchus

Syntopy

● Pulmonary arteries: Ventro-Caudal to the main right bronchus, Cranial to the Main Left Bronchus.

● Pulmonary Veins: Ventro-Caudal to the Main Bronchi.

● Aortic Arch: Superiorly convex, starts anteriorly to the left main bronchus 🡪 as it curves it becomes Superior and Finally 🡪 Posterior to the Right main bronchus.

● Azygos Vein: Ascends ventrally to the Right Main bronchus, arches over it 🡪 opens into SVC.

● Vagus nerves: Dorsal to the Main Bronchi

● Esophagus: Dorsal to the Left main Bronchi.

Blood Vessels, Innervation and Lymphatics

Neurovascular supply: Mixed Innervation - Per bronchial plexus: Vagus nerve

Blood supply: Bronchial Branches (from Thoracic Aorta, Posterior Intercostal arteries)

Venous Drainage: Bronchial veins (Into azygos vein, accessory Hemizygous vein, posterior intercostal veins)

Lymphatic Drainage: Intrapulmonary nodes (🡪 bronchopulmonary nodes 🡪Tracheobronchial bodes)