Owl
Owls have special adaptations which help them swivel their heads 270 degrees. They have 14 neck vertebrae instead of our seven. Also, the big carotid arteries, instead of being on the side of the neck as in humans, are carried close to the centre of rotation just in front of the spine. So these arteries get much less twisting and stretching, and the potential for damage is greatly reduced. This arrangement  is seen in other birds, but in owls the vertebral arteries – the vessels that travel through channels in the neck bones – are given extra space.