THE MUSCLES OF THE TONGUE. 



463 



M. Styloglossus. The styloglossus muscle arises from the anterior border 

 of the styloid process near its tip, and from the stylo-hyoid ligament. 



It sweeps forwards and medially, and is inserted into the side and inferior 

 surface of the. tongue, its fibres spreading out to decussate with those of the 

 i glossopalatinus and hyoglossus muscles beneath the submaxillary gland and the 

 mucous membrane of the tongue. 



M. Glossopalatinus. The glossopalatinus (O.T. palatoglossus) is a thin 

 sheet of muscular fibres arising from the inferior surface of the soft palate, where 

 it is continuous with fibres of the opposite muscle. 



It passes downwards, in the glosso-palatine arch, and spreads out, to be inserted 

 into the sides of the tongue, blending with the styloglossus and the deep transverse 

 fibres of the tongue. 



The muscle is placed directly beneath the mucous membrane of the soft palate 

 and tongue. 



B. Intrinsic Muscles of the Tongue. Besides receiving the fibres of insertion 

 of the extrinsic muscles, the substance of the tongue is composed of four intrinsic 

 muscles on either side two in the sagittal plane, the superior and inferior longi- 

 tudinal muscles ; two in the frontal plane, the transverse and vertical muscles. 



M. Longitudinalis Superior. The superior longitudinal muscle extends from 

 base to tip of the tongue. It is placed on its dorsum immediately under the 

 mucous membrane, into which many of its fibres are inserted. 



M. Longitudinalis Inferior. The inferior longitudinal muscle is a cylindrical 

 band of muscular fibres occupying the inferior part of the organ on each side, in the 

 interval between the genioglossus and the hyoglossus muscles. Posteriorly some 

 of its fibres extend to the hyoid bone. 



M. Transversus Linguae. The transversus linguae (O.T. transverse fibres) arises 

 from the median raphe, and radiates outwards to the dorsum and sides of the 

 tongue, intermingling with the extrinsic muscles and the fibres of the vertical 

 muscle. It occupies the substance of the tongue between the superior and inferior 

 longitudinal muscles. 



M. Verticalis Linguae. The verticalis linguae (O.T. vertical fibres) arises from 



the dorsal surface of the tongue, and sweeps downwards and laterally to its sides, 



; intermingled with the fibres of the preceding muscle and the insertions of the 



extrinsic muscles. The transverse and vertical muscles form a very considerable 



part of the total muscular substance of the organ. 



Nerve-Supply. All these muscles except the glossopalatinus are supplied by the hypo- 

 glossal nerve. The glossopalatinus is supplied by the accessory nerve through the pharyngeal 

 , plexus. 



Actions. The genioglossus and the hyoglossus are both elevators of the hyoid bone 



besides having actions in relation, to the tongue. The tongue is protruded by the action of the 



I posterior fibres of the genioglossus, retracted by the anterior fibres aided by the styloglossus. 



The styloglossus and glossopalatinus are elevators, while the genioglossus and hyoglossus are 



, depressors of the tongue. 



Actions of the Infra -hyoid and Supra -hyoid Muscles, and the Muscles of the 



Tongue. These muscles have a complexity of action, owing to their numerous attachments to 



more or less movable points. The movements for which they are responsible in whole or part are : 



L) movements of the hyoid bone in mastication and deglutition, (2) movements of the thyreoid 



cartilage, (3) movements of the tongue, (4) movements of the head, (5) movements of the shoulder, 



. and (6) respiration. 



) Movements of the Hyoid Bone. The hyoid bone is elevated or depressed, and moved for- 

 wards or backwards along with the mandible and tongue, in speech, mastication, and swallowing. 



