Fig. (3).

Histological cross-sections with trichrome staining through eight sets of human left pulmonary veins showing the variations in circumferential arrangement of the myocardial sleeves. Note the myocardial sleeve completely surrounding the superior vein and extending beyond 10 mm from the venoatrial junction in a male specimen. The sleeves are thicker in the sectors close to adjacent veins (arrows). Note myocardial strands/ bridges crossing the interpulmonary isthmus or carina between superior and inferior venous sleeves at the level of the venoatrial junction (broken arrow). LI, left inferior pulmonary vein; LS, left superior pulmonary vein;