There is an article in the current (Jan. 12) issue of the New Yorker, “Give Me a Smile” by Jonathan Kalb, who was struck by a not-all-that rare condition called Bell’s palsy that prevented him from smiling. I found it a moving example of personal journalism with wider aspects, such as the functions and importance of the smile.
If you’ve seen this article, you may wonder what the orbicularis muscle looks like and especially the platysma, which insists on pulling one corner of his mouth down so that he is forced into “an expression of joy spliced to an expression of horror.”
When I was trying to familiarize myself with some anatomy, I used to make monochrome drawings with color only over the muscle being portrayed. Here are just some of the muscles in and around the face.
The platysma is a crowd of fibers based on the collarbone – well outside the face – and yanking like fishermen hauling on a net.
Kalb mentions “a mustachioed young actor with the rare ability to move many of his facial muscles independently”; I’ve yet to find one I can’t so move, and had a party act of using auricularis to waggle my ears to separate rhythms. It seems that one I didn’t get around to portraying was the main smile-muscle, the zygomaticus that lifts the corner of the mouth