Anonymous Vein

ANONYM A VENA (truncus venosus brachiocephalicus), anonymous vein (brachiocephalic venous trunk). The paired A. v. is formed by the union of the v. jugularis int. with the v. subclavia. The site of their union lies behind the sternal end of the clavicle or lower, at the lig. costo-claviculare. The site of union at a right angle of the right and left A. v. is the beginning of the superior vena cava, which is the direct continuation of the A. v. dextra - is located to the right of the median line, below the cartilage of the I rib. The caliber of the A. v. is about 15 mm. Each of the two A. v. has its own characteristics. The A. v. dextra, of smaller caliber and shorter (from 3 cm, varying from 2-4 cm); its direction is almost vertical. Occupying the right part of the chest, it lies behind the cartilage of the I rib and the sternal end of the clavicle, from which it is separated by the inferior tendon of the mm. sterno-hyoidei and sterno-thyreoidi. Behind it lies the apex of the right lung, from which it is separated by a leaf of pleurae mediast., and the n. vagus. On the left, the A. v. goes together with the art. anonyma. The A. v. sinistra, of larger caliber, receives a greater number of branches and is longer than the right one (about 6 cm). Its position is almost horizontal; from left to right it crosses the median line, in front of it lies the sternal end of the left clavicle and the upper edge of the sternum; thus its pulse can be determined in the incis. jugularis. From the sternum it is separated by the inferior tendon of mm. sterno-hyoid. and sterno-thyreoid. and the gl. thymus or its remnants. Behind it lie the n. phrenicus, the n. vagus sin. and three arterial trunks of the aortic arch. The upper wall of it is free, while the lower rests on the aortic arch, why the A. v. sinistra is compressed in the case of an aortic aneurysm. The A. vv. have no valves, besides, they have the further peculiarity that they receive lymph ducts. Thus, into the right A. v. at the site of union of the v. jugul. and v. subcl. opens one or two lymph ducts (ductus lymphaticus dext.), into the left - ductus thoracicus (also at the venous angle). Injury to the A. v., besides bleeding, presents great danger to life due to the possibility of air embolism.