Anatomic variation of thorax drainage: absence of accessory hemiazygos vein

Formed by the azygos, hemiazygos and accessory hemiazygos veins, this system is responsible for the venous drainage of the thorax and partially of the abdomen. Abnormalities of this system are not uncommon, and many are referred to in literature. The complete agenesis of the accessory hemyazigos vein is associated with complete regression of the left posterior cardinal vein or atrophy of the left subcardinal vein. The reported case consists of the complete absence of the accessory hemiazygos vein, culminating in the drainage of the 4th, 5th, 6th, 7th and 8th left posterior intercostal veins directly into the azygos vein of a male cadaver. The importance of the theme is due to the necessity of recognizing patterns and frequencies of these variations when facing procedures addressing the mediastinum or the major vessels.

Sternalis muscle: an anatomic variation of the anterior chest wall

The sternalis muscle’s presence is an uncommon anatomic variation of the anterior chest wall’s musculature. It is insufficiently mentioned by the most of anatomical textbooks, although it has been well described by the literature. The study of this anatomic variation is extremely relevant, principally for the interpretation of image’s exams that approach this region. For this study’s achievement, 102 cadavers were dissected (97 of the male sex and 5 of the female sex). The study of the sternalis muscle avoids the expenses with exams and the indication of aggressive treatments in a wrong way.