See how the side view of the whole spine looks like the Rockettes dancing side by side, with their arms over each other's shoulders? Those overlapping transverse processes not only help lock the spinal column together and protect the spinal cord but they act as buttresses against too much torque.
Here some links to pictures and drawings of the cervical vertebrae of the neck and the joint between them and of the base of the skull and spinal cord
[I know I'm repeating but the Rockettes are a better teaser than "see these bones," or maybe not.]
See how the side view of the whole spine looks like the Rockettes dancing side by side, with their arms over each other's shoulders? Those overlapping transverse processes not only help lock the spinal column together and protect the spinal cord but they act as buttresses against too much torque. They are greatly reduced in the cervical vertebrae. That means the neck is more flexible but it is also more vulnerable than the rest of the spine.
Also the spinous processes, the lumps that you can feel down your backbone, over lap the next vertebrae and allow muscle attachment that helps link the vertebra to each other with skeletal muscle.
The trick of course is to have a system that is flexible but not too flexible, so there are flat sliding surfaces between the vertebrae but transverse processes and muscle to try to keep rotation within safe limits.
The 7 cervical vertebrae, the neck bones, do not have the robust transverse processes or long spinous processes of the rest of the spine but the cervical vertebrae do interlink more closely than the other vertebrae allowing more flexibility in our short neck with some recovery in resistance to over rotating.
The two vertebrae just below the skull, are referred to as the atlas and the axis, or technically the 1st and 2nd cervical vertebrae. The slightly convex occipital condyles of the skull rotate on the slightly concave surfaces of the atlas. That joint is a very weak joint, in that there are only two relatively flat surfaces sliding over on another, a bit like slightly cupping both hands placing the back of one hand on the palm of the other and rotating them back and forth. Essentially the same situation exists between the atlas and the axis, the axis and the 3rd cervical vertebrae
The head is held onto the shoulders mostly be the neck muscles and their tendons not by the bony articulations of the rest of the spine. Muscle and tendons can be stretched, strained and torn more easily than bone can be chipped or broken.
Owls basically have a saucer sitting on a saucer and can turn their heads about 90 degrees. Other birds are only slightly less limber. Thus it is rather easy to wring a bird's neck severing its spinal cord but rather more difficult to wring a human's neck. In either case the weakest joint is between the skull and the atlas/axis.
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So what happens when a person is lying on their stomach and someone puts their hands or knee and virtual their full body weight on one side of that person's head, turned 45 degrees from the normal position with their torso? Mostly because of the limitations of the large muscles and tendons of the neck but also because of the muscles and placement of the spiny processes of the vertebrae most of us do well to turn our heads that far. Obviously for younger people and some who are just really limber that is not a problem. I suspect most of us see that in the videos and mentally say ouch.
Think about the videos we have seen. The villain, soon to be victim, is on their stomach on the ground with a sweet heart of a guy crushing their head to the ground with all the manual force or body weighty they can muster. Another one or two are grabbing an arm or two and maybe even a leg, wrenching the extremities around, to cause maximum pain and resulting flinching of the, now, victim. "Stop resisting." they whine. The cops yank up an arm, even if the victim already has their hands behind their back, and twist thus making the arm fairly rigid and in that position forcing it back over the shoulder blade and then press it downward. More "Stop resisting."
If this is done right there is so much rigidity in the neck from being forced to the side and held in a vice, and separately in the arm, that either the shoulder of the neck has to dislocate or a bone has to break, or muscles and tendons tear. Certainly a lot of pain is the result.
The videos show that after Gray is lifted up his head is at an angle and he is crying in pain. His legs are dragging in rather odd attitudes, and the cops don't notice or care even though Gray had committed no crime, no act of violence or even threat of violence, and he seems to have difficulty holding his head erect.
The one shot that shows that Gray might have lifted his own leg to get into the van could well be the cop, who is masked from the camera actually lifting the leg. That leg flops back to the ground basically limp.
The cops do nothing to stabilize his neck at that point, and even if all that happened was that Gray had torn muscles or broken boney process(es) he would have had difficulty protecting his spinal cord as his head would have whip lashed around in the van, even if his body had been strapped in and it had been a fairly gentle ride.
Think about what happens to your head on a trip if you doze off in the passenger seat and the driver turns a corner abruptly. And that doesn't even begin to guess what would happen if Gray were being thrown headfirst around the metal walls of the van at 20 or more mph. Much less how the front of his throat was crushed. We knee'd to know that.
I find it difficult to understand that some medical group has not seen tapes of this type of take down and pointed out that it is really dangerous to hold the head at it's max rotation point while one or more other people are violently torqueing other parts of the body as all that torque is centering on the most important and one of the weakest joints in the body.
I'm also wondering if they rammed his head into that brick wall. That should show up in the autopsy, if so. Or if the axis or atlas show muscle tears, chips or cracks.
Trivia for the day. Back when I was a TA teaching Anatomy and Physiology lab, the only extra point question I ever used was to name as many bones as possible that articulated with the sphenoid bone, the bright pink one in the mjc, edu link. It is my favorite bone and is quite amazingly complex in its very very three-dimensional shape, and because of its location which makes it an important bone, as bones go. It is also the only bone of the skull that is visible from all 6 sides of the skull.