The vertebral artery
The vertebral artery is a branch of first part of subclavian artery. It lies posterior to inferior thyroid artery. It passes posterior to lateral mass of atlas.
Arises from the second part of subclavian artery , from behind scalenus anterior
Lies anterior to inferior thyroid artery
Passes through the C6 foramen transversarium
Passes anterior to the lateral mass of atlas and then enters the foramen magnum