1130 



THE DIGESTIVE SYSTEM. 



The mucous membrane of the tongue, like that of the rest of the mouth, is covered 

 by stratified squamous epithelium. 



Glandulse Linguales. Numerous small racemose glands are found scattered beneath the 

 mucous membrane of the posterior third of the tongue ; and a small collection of similar glands 

 is present at the margin, opposite the vallate papillae. Small serous glands are also found 

 embedded in the dorsum near the vallate papillae, into the fossae of which their ducts oren 

 (Fig. 891). _ 



The chief collections of glandular tissue in the tongue, however, are found embedded in the 

 muscle of the under surface, a little way posterior to the apex, on each side of the middle line 

 (Fig. 892). They are known as the glandulae linguales anteriores of Blandin or Nuhn. 



These glands are displayed after the removal, from the under surface of the tongue, of the 

 mucous membrane and a layer of muscle fibres about 2 mm. thick which is composed of fibres of 

 the styloglossus and the longitudinalis inferior muscles a little distance behind the apex. The 

 anterior lingual glands are oval in shape, often partly broken up by muscular fibres, and they 

 measure from to f in. (12 to 19 mm.) in length. They are mixed serous and mucous glands, 

 and they open by three or four very small ducts on the inferior surface of the tongue. 



Vallate papillae 



Styloglossus 



Stylo-hyoid 



Superficial lymph 

 vessels of side and 

 dorsurn of tongue 



Lymph vessels 



of apex of 



tongue 



Afferents to 

 mandibu 

 glands 



Sublingual gland 



Submental gland 



Mylo-hyoid cut' 



Afferent to deep cervical glands ' 

 Anterior belly of digastric (cut) ' 



Digastric 



Afferents to 

 deep cervical 

 glands from 

 posterior third 

 of tongue 



Common facial vein 



Upper deep cervical 

 lymph glands 



Omo-hyoid 



FIG. 894. LYMPH VESSELS OF THE TONGUE (after Poirier and Cuneo, modified). 



Vessels. The chief artery is the lingual. This vessel passes forwards, on each side, medial to 

 the hyoglossus muscle, and then is continued on to the apex between the genioglossus on the 

 medial side and the longitudinalis inferior laterally under the name of the a. profunda linguae. 

 Anteriorly it is covered by the fibres of the longitudinalis inferior, and lies to in. from 

 the surface. Near the apex the arteries of opposite sides are connected by a branch which 

 pierces the septum ; but otherwise, with the exception of capillary anastomosis, they do not com- 

 municate. The rami dorsales linguae of the lingual artery are distributed to the pharyngeal part 

 of the tongue, whilst some twigs of the ramus tonsillaris of the external maxillary artery are 

 also distributed in the same region. 



The veins are : The v. profunda linguae, the chief vein, which lies beneath the mucous 

 membrane at the side of the frenulum, and runs backwards over the hyoglossus with the 

 hypoglossal nerve ; two venae comites, which accompany the lingual artery ; and two dorsalis 

 linguae veins from the back of the tongue. These either unite and form a common trunk, 

 or open separately into the internal jugular vein. 



The lymph-vessels of the tongue take their origin in an extensive lymph network in the 

 submucous coat, and a smaller network connected with the first, in the muscular substance of 

 the tongue. The network at the apex, including the tip, margins, and front of the dorsum, is 

 drained by some two to four vessels on each side, which pass downwards by the margin of the 

 genioglossus muscle and pass laterally to the inferior deep cervical lymph glands. These vessels 

 may be connected with the submental lymph glands also. 



From the margins and dorsnm of the tongue, behind the former area, and extending back to 

 the vallate papillae, lymph- vessels pass to the submaxillary lymph glands, and also, on the hyo- 



