Invagination of the mucosa between the birth of two bronchi.
Distribution anomaly: Tracheal bronchus.
Part of the right upper lobe is ventilated thanks to a bronchus that has shifted during the embryonic phase of lung development so that it is born directly from the trachea.
Sometimes, this bronchus only leads to the apical segment of the right upper lobe and is, in these cases, a “supernumerary” bronchus.
It can be associated to the fusion of cervical vertebrae (syndrome of Klippel Feil).