The Sphincters (Development series, installment 2)

Humans, it turns out, are born with more than the skull incompletely formed. Apparently our digestive tract (despite being part of the earliest independent differentiations of the embryo*) is immature at birth, and we have to figure out how to use it. I hadn’t realized this until someone pointed out to me that this was the reason for all of Noam’s staining and grunting when he was just a few weeks old.

Here he is at about two months:

(Sorry the flash takes a while to load.... Anyone know how to force this thing to buffer?)

Notice how his whole body gets involved in the act of digestion? Check out his lips beginning around the 15th second. You can see that the lips are clearly a sphincter, and that for him they are not completely differentiated from the rest of the digestive process yet. Because he’s swaddled, you can’t see how his hands clench and unclench, but you can see the ripple through the whole system. Truly we have so much in common with the lowly worm!

I owe the observation that we have more sphincters than we usually think about to the work of Ruthy Alon. I put this lesson together with help from a lesson of hers I did a long time ago as well as some of her more recent Bones For Life work.

I’m happy with the way it came out. The experience was quite profound for several of my students. Try it out, and let me know what you think!

Coming soon: the diaphragm!

*Myers, Thomas. Anatomy Trains pp. 36-39. Anyone want to find me an online citation?