NORMAL HISTOLOGY. 



to the amount and character of this layer the mobility of the oral lining varies. 

 Where plentiful and loose, as over the floor of the mouth, the mucosa is 

 freely movable, while over the hard palate and the alveolar processes of the 

 jaws the submucous tissue is so meagre that the mucous membrane is almost 

 directly blended with the periosteum and correspondingly fixed. 



The blood-vessels supplying the oral mucous membrane are numer- 

 ous, the larger stems occupying the submucous layer, within which they 

 form a wide-meshed network. Thence the twigs pass into the tunica 



Labial glands 



Integument 



Sebaceous gland 



Fibres of 

 orbicularis oris 



Transition into 



true mucous 



membrane 



Modified mucous 

 mem bran 



Transition into 

 modified skin 



FIG. 170. Sagittal section of lip of young child, showing transition of skin into oral mucous 



membrane. X 20. 



propria, where they form a second and closer network. Their ultimate dis- 

 tribution includes capillary loops that occupy the papillae, the smaller eleva- 

 tions containing only one or two terminal loops and the large ones a tuft of 

 half a dozen or more. The lymphatics are represented by a network of 

 lymph-spaces within the tunica propria which drain into the wide-meshed 

 reticulum of definite lymph-channels within the submucous layer. The 

 nerves are chiefly medullated fibres that assume a loose plexiform arrange- 

 ment within the submucosa. From here numerous twigs enter the tunica 

 propria and break up into the component fibres, which mostly terminate in 

 the stroma and papillae either free or in connection with end-bulbs or tactile 

 corpuscles. A few fibres, after losing the medullary coat, penetrate the 

 epithelium and, after repeated branching, end between the epithelial cells as 

 naked axis-cylinders. 



