THE FAUCES 



1137 



The ducts are lined at their origins by epithelium which differs little from the pavement form. 

 As the ducts enlarge, the epithelial cells change to the columnar type, and the part of the cell 

 next the basement membrane is finely striated. 



The lobules of the salivary glands are richly supplied with bloodvessels which form a dense 

 net-work in the interalveolar spaces. Fine plexuses of nerves are also found in the interlobular 

 tissue. The nerve fibrils pierce the basement membrane of the alveoli, and end in branched 

 varicose filaments between the secreting cells. In the hilus of the submaxillary gland there is 

 a collection of nerve cells termed Langley's ganglion. 



Fia. 1025. Section of submaxillary gland of kitten, 

 semidiagrammatic. X 200. 



Duct FIG. 1026. Human submaxillary gland. (R. Hei- 



denhain.) At the right is a group of mucous alveoli, 

 at the left a group of serous alveoli. 



Accessory Glands. Besides the salivary glands proper, numerous other glands are found 

 in the mouth. Many of these glands are found at the posterior part of the dorsum of the tongue 

 behind the vallate papilla, and also along its margins as far forward as the apex. Others lie 

 around and in the palatine tonsil between its crypts, and large numbers are present in the soft 

 palate, the lips, and cheeks. These glands are of the same structure as the larger salivary glands, 

 and are of the mucous or mixed type. 



THE FAUCES. 



The aperture by which the mouth communicates with the pharynx is called 

 the isthmus f aucium. It is bounded, above, by the soft palate ; below, by the dorsum 

 of the tongue; and on either side, by the glossopalatine arch. 



The glossopalatine arch (arcus glossopalatinus; anterior pillar of fauces) on either 

 side runs downward, lateralward, and forward to the side of the base of the tongue, 

 and is formed by the projection of the Glossopalatinus with its covering mucous 

 membrane. 



The pharyngopalatine arch (arcus pharyngopalatinus; posterior pillar of fauces') is 

 larger and projects farther toward the middle line than the anterior; it runs down- 

 ward, lateralward, and backward to the side of the pharynx, and is formed by the 

 projection of the Pharyngopalatinus, covered by mucous membrane. On either side 

 the two arches are separated below by a triangular interval, in which the palatine 

 tonsil is lodged. 



The Palatine Tonsils (tonsillce palatina; tonsil) are two prominent masses situated 



one on either side between the glossopalatine and pharyngopalatine arches. Each 



tonsil consists fundamentally of an aggregation of lymphoid tissue underlying 



the mucous membrane between the palatine arches. The lymphoid mass, however, 



72 



