I really shouldn't pursue this. The answer is probably obvious and I'm just being dense.
Here's a picture (above) that seems to confirm Mark's opinion. The cheeks don't bunch up much, maybe because the skin is spread all over the side of the face. Boy, this face resembles a screaming baboon!
The small picture on the lower left (above) is interesting. It shows the lower jaw receding backwards into the face as the woman laughs. The upper teeth don't seem to move much.
Of course it's an effort to hold a smile very long. You get tired of keeping the cheeks up. When the strain becomes unbearable (above) you stop supporting the cheeks and the meat collapses downward, back into it's home in the muzzle.
Of course it's an effort to hold a smile very long. You get tired of keeping the cheeks up. When the strain becomes unbearable (above) you stop supporting the cheeks and the meat collapses downward, back into it's home in the muzzle.
I've seen lots of flabby muzzles, especially on middle aged men and Star Wars fans.