A mental spine is a small projection of bone on the posterior aspect of the mandible (lower jaw bone) in the midline. The adjective mental in this instance is used in its "chin-related" sense (from Latin mentum) rather than its more common "mind-related" sense (from Latin mens). There are usually four mental spines: two superior and two inferior. Collectively they are also known as the genial tubercle,genial apophysis and the Latin name spinae mentalis. The inferior mental spines are the points of origin of the geniohyoid muscle, one of the suprahyoid muscles and the superior mental spines are the origin of the genioglossus muscle, one of the muscles of the tongue.