THE HYPOGLOSSAL NERVE 



953 



glossus muscle it lies immediately above the raniae vein. It is crossed by the posterior belly 

 of the digastric and the stylo-hyoid muscle, and it is covered superficially, behind the mylo- 

 hyoid, by the lower part of the submaxillary gland. 



Communications. — The Itypoglossus is connected with the first cervical gan- 

 glion of the sympathetic, with the ganglion nodosum of the vagus, with the loop 

 between the first and second cervical nerves, and with the lingual nerve; the 

 latter communication is estabhshed along the anterior border of the hj^o-glossus 

 muscle (figs. 743 and 744). 



Terminal branches.— These include (1) a meningeal branch; (2) branches from 

 the cervical plexus; and (3) branches from the hj-poglossus proper. 



(1) A meningeal branch, frequently represented by two filaments, is given off in the hypo- 

 glossal (anterior condyloid) canal. It passes backward into the posterior fossa of the cranium 

 and is distributed to the dm-a mater. It was believed at one time that the fibres of the meningeal 

 branch were derived from the lingual nerve, but it is now deemed more probable that they are 

 either sensory or visceral motor fibres from the cervical nerves, or from the vagus. 



Fig. 743. — The Hypoglossal, 



Ganglion nodosum 

 Cut surface of the styloid 

 process 



Internal jugular 

 vein 

 Facial nerve 

 (cut off) 

 Spinal accessor: 

 (external branch 

 Transverse proc- 

 ess of atlas 

 Anterior branch 

 of first cervical 

 nerve 

 ,. f Of vagus — 



^ u«„ 1 so -pha- —. 

 ranches | ry^geal 



.nterior branch of 

 econd cervical nerve 



Stylo-pharyngeal 



branch 

 Stylo-pharyngeus 



Hypoglossal nerve 



External carotid artery 



Anterior branch of 

 third cervical nerve 

 Descendeus cervicalis 

 (hypoglossi) 

 interior branch of fourth 

 cervical nerve 

 Sterno-mastoidetis 



Vagus j 



Ansa cervicalis 

 (hypoglossi) 



Phrenic nerve 



Glosso-pharyngeal, and Lingtjal Nerves. (Spalteholz.) 



Glosso- Internal 

 pharyngeal carotid Semilunar 

 nerve artery ganglion 



Ophthalmic 

 nerve 



- Maxillary 



nerve 

 Mandibular 

 ■ nerve 

 Lateral plate 

 — of pterygoid 



process 

 Chorda 



tympani 

 Tensor veli 

 ^ palatini 

 Lingual nerve 



Buccinator 

 Branches to 

 isthmus of 

 fauces 



stylo- 

 glossus 



Lingual 



branches of 

 lingual nerve 

 ^"., Sublingual 



^ nerve 

 ""s Anastomotic 

 % £"^ ^N-branch to 

 ^'^^ \ hypoglossal 

 — -^^^ ^Genio-glossus 



Lingual branches 

 of hypoglossal 

 N Genio-liyoideus 

 Hyoglossus 



Thyreo-hyoid branch 



'] ^ Lingual artery 



Superior thyreoid artery 



Thyreo-hyoideus 



Branch to the sterno-hyoideus 

 Common carotid artery 



(2) Branches which consist of fibres derived from the cervical plexus. — The descendens 

 cervicalis (hypoglossi) and the muscular twig to the thyreo-hyoid muscle, though apparently 

 arising from the hypoglossal nerve, consists entireh^ of fibres which have passed into the hypo- 

 glossal nerve from the loop between the first two cervical nerves. Therefore, neither of them 

 are branches of the hypoglossus proper. (See fig. 752.) 



(a) The descendens cervicalis (hypoglossi) parts company with the hypoglossus at the point 

 where the latter hooks around the occipital artery (fig. 74.3). It runs do^Tiward and slightly 

 medialward on the sheath of the great vessels (occasionally within the sheath), and is joined 

 at a variable level by branches from the second and third cervical nerves, forming with them a 

 loop, the cervical loop [ansa hypoglossi] (fig. 743). The cervical loop may be placed at any level 

 from a point immediately below the occipital artery to about four centimetres above the sternum. 

 From this loop all the muscles attached to the hyoid bone are supphed. A twig to the anterior 

 belly of the omo-hyoid arises from the descendens cervicalis in the upper part of its course. 

 The nerves which supply the sterno-hyoid, sterno-thyreoid, and posterior belly of the omo- 

 hyoid are given off by the cervical loop. Twigs from the first two nerves pass downwai-d in 

 the muscles behind the manubrium sterni and^in rare cases communicate with the phrenic 



