口、歯、頭、顔を使った慣用表現

Here is a list of several common expressions using 頭 and 顔：

頭が抱える： To be at a loss for what to do; to be perplexed.
頭が上がらない：　To be in the dog house; to be unable to stand up to X.
頭が下がる： To "tip your cap" (as a term of respect) to someone.
顔が広い： To be well- known.
顔が利く：　To have pull.

The following are ones using 口 and 歯：

開いた口をふさがらない： Jaw-dropping.
口を出す： Butt-in.
口をそろえて： In one voice; unanimously.
口がすべる： To let (words) slip out.
口をすべらせる: SAME.
口が軽い： To have a loose tongue.
口が堅い： To be able to keep a secret.
歯が立たない： Impossible to match.