Variable relationships of accessory nerves, phrenic nerves, and ansa cervicalis to the great veins. Studies in the laboratory showed that accessory nerve crossing anterior to the internal jugular vein in 70 percent of 188 specimens. The phrenic nerve passes posterior to the site of the union of the subclavian, internal jugular, and brachiocephalic veins.

Image courtesy of Grant's Atlas of Anatomy

Internal jugular vein and its tributaries

Note the dilation, or the bulb, at each end of the internal jugular vein. The superior bulb is separated from the floor of the middle ear by a delicate bony plate. The inferior bulb, like the corresponding bulb at the end of the subclavian vein, contains a bicucuspid valve that permits the flow of blood towards the heart. There are no valves in the brachiocephalic veins or superior vena cava.

Image courtesy of Grant's Atlas of Anatomy

Superficial Veins

Outside the skull, superficial temporal and maxillary veins form the retromandibular vein, whose posterior division unites with the posterior auricular vein to form the external jugular vein. The facial vein receives the anterior division of the retromandibular vein before emptying into the internal jugular vein.

Image courtesy of Grant's Atlas of Anatomy