NOMENCLATURE FOR PERIPHERAL BRONCHI
Two nomenclature systems are commonly used to identify the segmental
anatomy of the lungs. The one proposed by Boyden uses numerical ordering, and
the one proposed by Jackson and Huber names the bronchi. It is recommend that
one become familiar with both systems.
There are 10 segments in the right
lung and nine in the left (see Plates 1-14 and 1-15). Subdivisions of the bronchial
tree correspond to the anatomic segments and are named accordingly. These
tertiary bronchi were regarded by Jackson and Huber as the final branches, but
the advent of the flexible bronchoscope led Ikeda to introduce additional
nomenclature for the fourth, fifth, and sixth divisions because these can now be
visualized. A convenient numerical system is used in which segmental bronchi
are numbered from 1 to 10 on each side and identified by the capital letter B
for bronchus. This may be prefixed by a capital letter R for right
and L for left, so that RB3 identifies the bronchus to the anterior
segment of the right upper lobe. The apicoposterior segment of the left upper
lobe is LB1+2, and the anteromedial basal segment of the same side becomes
LB8 because each of these paired segments is supplied by a single
tertiary bronchus. With rare exceptions, there is no LB7 designation.
Subsegmental or fourth-order
bronchi are indicated by the lower case letter a for posterior and b for
anterior. The letter c may also be used when necessary for additional
bronchi.
Fifth-order bronchi are designated
by the Roman numerals i (posterior) and ii (anterior). Finally,
those at the level of the sixth order of division are characterized by α and β.
Endobronchial variations from the
normal anatomy are frequent and are more common in peripheral airways.
