Activity of extrinsic tongue muscles during swallowing in sheep.

The participation of extrinsic muscles of the tongue in swallowing reflexly induced by stimulation of the superior laryngeal nerve was studied in 7 anesthetized sheep. The tongue retractor muscles (styloglossus and hyoglossus) always discharged in synergy with the suprahyoid (geniohyoid) and jaw (anterior digastric and medial pterygoid) muscles. The main protrusor muscle of the tongue, the genioglossus, was inactive in 5 animals and active in 2. The significance of this muscular synergy is discussed.