How many facial tissues or muscle do we use while yawning?

Many, 12.How many facial tissues or muscle do we use while yawning?
http://www.intelligenthumor.com/adventur鈥?/a>


http://linkinghub.elsevier.com/retrieve/鈥?/a>


http://www.springerlink.com/index/V13483鈥?/a>