Human Anatomy Vol 1

Eparterial bronchus

Pulmonary artery

Hyparterial bronchus

Anterior pulmonary plexus

Superior and inferior

pulmonary veins

Posterior pulmonary

plexus

Bronchial vessels

Lymph vessels and

bronchopulmonary

lymph nodes

Areolar tissue

Right Left

Fig. 16.4: Roots of the right and left lungs seen in section

Posterior

Superior

lnferior

Lungs

Pulmonary artery

Anterior pulmonary plexus

Bronchus

Superior and inferior

pulmonary veins

Bronchiqllree

The trachea divides at the level of the lower border of
the fourth thoracic vertebra into two primary principal
bronchi, one for each lung. The right principal bronchus
is 2.5 cm long. It is shorter, wider and more in line with
the trachea than the left principal bronchus (Fig. 16.5).
Inhaled particles or foreign bodies therefore, tend to
pass more frequently to the right lung, with the result
that infections are more common on the right side than
on the left.
Tlae left principal bronchus is 5 cm. It is longer,
narrower and more oblique than the right bronchus.
Right bronchus makes an angle of 25" with tracheal
bifurcation, while left bronchus makes an angle of 45'
with the trachea.
Each principal bronchus enters the lung through the
hilum, and divides into secondary lobar bronchi, one for
each lobe of the-lungs. Thus there are three lobar
bronchi on the right side, and only two on the left
side. Each lobar bronchus divides into tertiary or
segmental bronchi, one for each bronchopulmonary
segment; which are 10 on the right side and L0 on the
left side. The segmental bronchi divide repeatedly to
form very small branches called terminal bronchioles.
Still smaller branches are called respiratory bronchioles
(Fig. 16.6).
Each respiratory bronchiole aerates a small part of
the lung known as a pulmonary unit. The respiratory
bronchiole ends in microscopic passages which are
termed:
1 Alveolar ducts (Fig. 16.7)
2 Atria.

3 Air saccules.

4 Pulmonary alveoli (Latin small cauity). Gaseous

exchanges take place in the alveoli.

Bronchopulmonory Segmenls

The most widely accepted classification of segments is

given in Table 16.3. There are (^10) segments on the right
side and^10 on the left (Figs 16.5 and 16.8).
#efiniti*n
1 These are well-defined anatomic, functional and
surgical sectors of the lung.
10
Fig. 16.5: Bronchopulmonary segments of the lungs
Posterior
Right