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Is there any skeletal muscle that does not have an antagonist? Excluding circular muscles such as around eye and mouth.

The reason why I am wondering is because in biology normally nothing is ever just like that, there is always an exception. This would be the first biological rule without exception that I came across.

I am thinking of humans only for a start but feel free to include any other animal if any have skeletal muscles without antagonists :)

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"the first rule without exception?" Didn't you just say - "excluding orbiculares"? –  John C May 24 '12 at 9:58
    
Good point, of course everyone can decide what exactly the rule should be and adding conditions removes exceptions. But that's not really what my question was about :-) –  Armatus May 24 '12 at 13:29
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up vote 5 down vote accepted

I would argue that the orbiculares do have antagonists. To some extent, levator palpebrae superiorus antagonizes orbicularis oculi, and zygomaticus major/minor as well as risorius antagonize orbicularis oris.

I can think of three muscle that don't have obvious antagonists:

  1. Stapedius
  2. Tensor tympani
  3. Articularis genu

1 and 2 essentially perform the same action, to dampen sounds reaching the cochlea. 3 elevates the suprapatellar bursa.

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