The surgical anatomy of the pulmonary vessels.

Surgical resections of the lung have in recent years become common and relatively safe procedures. Depending upon the extent and nature of the disease process, the whole lung, one or two lobes, or one or more bronchopulmonary segments may require excision. Modern pulmonary resection depends to a very large extent upon the precise identification of the primary, secondary, and tertiary hilar bronchovascular structures, and it has thus become essential to have a detailed knowledge of the anatomy of these structures at the different hilar levels. The aim of this paper is to describe and to illustrate this anatomy. It is based upon a study of 42 complete casts of the bronchovascular tree and the hilar anatomical findings displayed during the course of 92 partial and 30 whole lung resections performed by some members of the Thoracic Surgical Unit, Johannesburg, during the past year. The pulmonary vessels and the bronchi are illustrated chiefly from such approaches as are used by the surgeon when dissecting the different primary, secondary, and tertiary hila. Each lung, anatomically, is composed of 10 bronchovascular or bronchopulmonary segments. These segments are miniature lobes differing from lobes only in their size and in the usual absence of fissures at their anatomical boundaries. A lobar bronchus branches from a main bronchus at a relatively constant site, and subdivides in a more or less standard fashion into its segmental bronchi. The pulmonary artery, however, has not this same lobar distribution, and although the segmental pulmonary arteries follow the segmental bronchi somewhat closely, they tend to have a variable and independent origin from the pulmonary artery. The segmental artery, like the segmenital bronichus, occupies a central position within the bronchopulmonary segment. The blood carried to the segment by such a centrally situated artery is collected by perisegmental pulmonary veins; as such, they are either placed superficially, immediately beneath the pleura, or deeply, in an intersegmental plane. The intersegmental veins drain also adjacent segments within a lobe and may drain adjoining segments of a different lobe. In the latter instance the veins pass subpleurally across the base of a fissure. The perisegmental (intersegmental or segmental) veins course somewhat independently of the segmental bronchi and arteries to reach the subp'eural plane in the primary hilum and there join a main pulmonary vein.