WILTIMS #37: In need of an atlas... no the other kind

A drawing from my Netter Atlas of  Human Anatomy

As usual, the day after an intense test we are buried under an avalanche of new information. In anatomy, we have moved on to the back and extremities. But there are no organs, you say? Should be a cinch, you add? Pfft! There are more muscles and nerves than you can shake a stick at... and you'd be using dozens of them to shake the stick in the first place.

Anyways, lots of new info means a bunch of cool facts for you guys! Enjoy.

TIL: The first vertebra is called the atlas because, like the ancient Greek titan of the same name, it holds the globe in its hands. The weight of the entire head is balanced on just the two articular surfaces of this bone.

Statue of Atlas at 30 Rock

The axis is the 2nd vertebra and it has a structure called the dens which reaches up into the atlas, providing support analogous to the vertebral bodies of lower vertebrae. If a person's dens is abnormally long, it can pierce the spinal cord upon hyperflexion of the neck, killing the person "which can be a problem," as per my professor today.

Another developmental defect can be the formation of the ponticulus posticus, a small abnormal bridge of bone on the atlas that can cause a presenting person to pass out by pinching off the vertebral artery when they tilt their head back too far. This defect is more prevalent in women and can be found while at a hair salon when the hairdresser goes to wash the woman's hair and she loses consciousness in the chair.

There is a set of muscles in the back that do nothing, or rather they don't move anything as one would expect a muscle to do. These muscles have instead been found to be proprioceptive, meaning they provide sensory input to the brain about their relative level of tension, allowing one to better gauge the stresses being placed on one's back.

The lower part of the spinal cord looks very similar to the tail of a horse and thus is quite literally named cauda equina or "horse tail" in latin.