Appendix 1: Anatomy and
development of the lungs (Fig. 47.36)
During the fourth week of intrauterine growth the lung bud develops from
the ventral surface of the primitive foregut.
The
primitive lungs drain into the cardinal veins which ultimately become the
pulmonary veins draining into the left atrium. Abnormalities of venous drainage
may occur at this stage of development (compare anomalous venous drainage).
Surgical
anatomy of the lungs
There are three lobes to the right lung and two to the left, although
the two sides are basically very similar (Fig. 47.37). Each lobe is composed of
segments (see above) with its own discrete blood supply of pulmonary artery and
pulmonary vein: an important point when resecting individual segments. No
bronchi or arteries cross the intersegmental plains.
The
right main bronchus is shorter, wider and nearly vertical compared with the
left. As a consequence, inhaled
Lymphatic
drainage tends to follow the bronchi and certain collections of lymph nodes are
recognised around the hila and trachea (Fig. 47.40).
These
are important as their presence or absence is useful in staging malignant
disease (noninvasively by radiography or invasively by needle biopsy,
mediastinotomy or mediastinoscopy). They are also important in determining
prognosis following resection of a lung neoplasm.