The bronchi are airway passages that conduct air from the trachea to the lungs. They form a bronchial tree as the large bronchi branch into smaller bronchi and bronchioles.

The bronchial tree starts at the tracheal bifurcation with the right main bronchus and left main (principal) bronchus that branch into smaller bronchi. The bronchial tree is composed of the following bronchi (from the largest to the smallest):

The right and left main bronchi arise at the level of the 4th to 5th cervical vertebrae (C4 - C5). Each main bronchus divides into lobar bronchi.

The right lung receives three lobar bronchi (superior, middle and inferior) while the left - two (superior and inferior). The number of lobar bronchi in each lung corresponds to the number of lung lobes.

Each lobar bronchus in lung segments divides into segmental bronchi, which further divide into subsegmental bronchi. The number of the segmental bronchi in each lung corresponds to the number of the bronchopulmonary segments the lung has.

Finally, the smallest subsegmental bronchi divide into bronchioles. Bronchioles are small airways with a diameter of 0.5 - 1 centimeters. Each bronchiole divides into smaller bronchioles within the lungs until the terminal bronchiole, which is approximately 0.5 millimeters wide.

The terminal bronchiole marks the transition place as the bronchial tree transitions into the alveolar tree, which is the respiratory part of the lungs.

Unlock with Premium

Bronchi