The extrinsic muscles of tongue make up the muscular base of this organ. Some anatomists also refer to them as the skeletal muscles of tongue, since they are attached to bone. They are four muscles as two of them take part in deglutition (process of swallowing food). They are innervated by the hypoglossal nerve (CN XII) and supplied by the deep lingual and sublingual arteries, which are branches of the lingual artery.
1) Styloglossus muscle– It originates from the styloid process of temporal bone and the stylohyoid ligament, traveling obliquely downwards and forwards, joining the lateral aspect of the root of tongue. Function: it pulls the tongue backwards and upwards.
2) Hyoglossus muscle– It is square in shape, rising from the superior border of the body and the greater horn of the hyoid bone, with its fibers running upwards to insert to the side of the tongue, between the styloglossus and inferior longitudinal muscle. Action: it pulls the tongue backwards and downwards.
3) Genioglossus muscle– Lying on both sides of septum of tongue, it arises from spina mentalis of mandible and then runs up as it fans out to insert into the lingual fascia and the mucous membrane of tongue. Its posterior fibers insert into the body of the hyoid bone. It pulls the tongue forwards and downwards.
4) Chondroglossus muscle– It originates from the lesser horn of the hyoid bone and runs upwards, together and confused with the hyoglossus fibers. It is inserted into the dorsum of tongue.
Below, schematic picture of extrinsic muscles of human tongue. The chondroglossus cannot be seen because it runs between the muscular fibers of the hyoglossus muscle.
