SEVEN - CARDIAC BRONCHOPULMONARY SEGMENT LEFT INFERIOR LOBE
The medial basal bronchopulmonary segment of the left inferior lobe is supplied by the medial basal segmental bronchus, a branch of the left inferior lobe bronchus. Occasionally, it arises from a common segmental bronchus with the anterior basal segment.
This segment only has medial and diaphragmatic surfaces which are not enclosed by surrounding segments. Anteriorly is the lower end of the oblique fissure; directly anterior to the fissure is the inferior lingular segment of the left superior lobe. Posteriorly is the posterior basal segment of the inferior lobe. Posterosuperiorly is the apical segment of the left inferior lobe. Directly superiorly is the hilum of the left lung.
Inferiorly, the medial basal segment rests upon the surface of the diaphragm. Laterally is the lateral basal segment of the inferior lobe and, in a significant percentage of the population, a subapical segment superior to this.
Medially, the surface of the medial basal segment forms the posterior part of the cardiac impression on the left lung. The effect of developmental pressure on the segment from the medially-sited heart results in it being relatively small compared to the equivalent medial basal segment in the right lung.