OsteoMenagerie 7: The Vertebrae

Word on the street is that the third polar vortex will hit Michigan later this week. After trudging through this year’s record amounts of snowfall, shivering angrily at the bus stop while the temperature experiments with establishing its true seasonal nadir (-20˚C? Nah, let’s live a little. Aim for -30!), and staring forlornly out the window, pining for the sun, I am ready for a break. In the spirit of truly throwing in the towel until spring hits, I’m dedicating this week to the easiest of osteomenageries: the vertebrae.

Admittedly, I’ve already discussed how easy it is to identify categories of vertebrae by using the superior articular facets. However, if you want to quickly identify whether an isolated vertebra is cervical, thoracic or lumbar,  have I got a trick for you. We’ll start low and work our way up.

1. Lumbar vertebrae look like moose. Orient the vertebra so that the spinous process is facing you, and the superior articular facets are up (as if the vertebrae were in anatomical position in the spine of someone standing immediately in front of you).

Left: Lumbar vertebra, posterior view
Right: Moose, disgruntled view

See? It’s now impossible to unsee. The superior articular facets look like moose antlers, while the purportedly “hatchet-shaped” spinous process is inarguably a large, clunky moose nose.

Left: Lumbar vertebra, lateral view
Right: Moose, contented view

2. Thoracic vertebrae resemble giraffes. The superior articular facets are both positioned so that they face straight back posteriorly, and are relatively evenly spaced and flat….much like the horns of a giraffe.

Left: Thoracic vertebra
Right: Bemused giraffe

The transverse processes are short and flare laterally, just like giraffe ears. Similarly, the spinous process of the thoracic vertebrae is much thinner and more gracile than that of the lumbar vertebrae, making it look far-more giraffe-like in lateral view:

Left: Thoraric vertebra, lateral view
Right: Giraffe, longing for summer

3. The cervical vertebrae look like extremely happy fish. Admittedly, this one is a little bit more of a stretch, but if you orient the cervical vertebrae so that the transverse foramina are highest up, while the spinous process points down (basically the position you would be in if you were behind someone, staring straight down their spinal cord while hovering above their head), you’ll see it. In this position, the transverse foramina resemble eyes, the superior articular facets resemble pectoral fins, and the spinous process looks like a pelvic fin. As a caveat, this only works for C3-C7. C1 and C2, the atlas and axis, are structurally distinct from the ‘regular’ cervicals because of their articulation with each other and with the occipital bone.

Left: Puffer fish, unpuffed
Right: Cervical vertebra, superior view

Another easy way to identify the cervical vertebrae is that they tend to be the only vertebrae that have bifurcated spinous processes. They are also unique in their transverse foramina, which accommodate the vertebral vein and artery.

Transverse foramina indicated with blue arrows. Bifurcated spinous process indicated with red arrows.

Alright. That was your osteology lesson for this week. I’m now going to curl up in bed, pull the blankets over my head, and stare at this photo of a hippopotamus getting a birthday cake until spring arrives.

Image Credits: Lumbar in posterior view here, associated moose here. Lumbar in lateral view here, associated moose here. Thoracic in posterior view here, associated giraffe here. Thoracic in lateral view here, associated giraffe here. Happy fish here, cervical in posterior view here. Cervical with birfurcated spinous process found here.