Original: Protrusion of the tongue is achieved by contracting the circular muscles that change the shape of the tongue and force it forward, and contraction of two genioglossal muscles attached to the caudal end of the tongue and to the mandible.
Simplified: Sticking out the tongue is achieved by contracting the circular muscles that change the shape of the tongue and force it forward, and contraction of two muscles attached to the caudal end of the tongue and to the mandible.