1228 THE ORGANS OF DIGESTION 



The deep process of the gland extends forward and inward between the Mylo- 

 hyoid below and externally, and the Hyoglossus and Styloglossus internally; 

 above it is the lingual nerve; below T it, the hypoglossal nerve and ranine vein. 



The duct of the submaxillary gland, or Wharton's duct (ductus submaxillaris [Whartoni]}, is 

 about two inches in length, and its wall is much thinner than that of the parotid duct. It begins 

 by numerous branches from the deep portion of the gland which lies on the upper surface of 

 the Mylohyoid muscle, and runs forward and inward between the Mylohyoid and the Hyoglossus 

 and Geniohyoglossus muscles, then between the sublingual gland and the Geniohyoglossus 

 muscle, and opens by a narrow orifice on the summit of a small papilla (caruncula sublingualis) 

 at the side of the frenum linguae. On the Hyoglossus muscle it lies between the lingual 'and 

 hypoglossal nerves, but at the anterior border of the muscle it is crossed by the lingual nerve. 



Vessels and Nerves. The arteries supplying the submaxillary glands are branches of the 

 facial and lingual. Its veins follow the course of the arteries. The lymphatics drain into the 

 submaxillary lymph nodes. The nerves are derived from the submaxillary ganglion, through 

 which it receives filaments from the chorda tympani and from the lingual branch of the inferior 

 maxillary, sometimes from the mylohyoid branch of the inferior dental and from the sympa- 

 thetic. 



The Sublingual Gland (glandula sublingualis) (Fig. 946) is the smallest of the 

 salivary glands. It is situated beneath the mucous membrane of the floor of 

 the mouth, at the side of the frenum linguae, in contact with the inner surface 

 of the mandible, close to the symphysis. It is narrow, flattened, in shape some- 

 what like an almond, and weighs about a dram. It is in relation, above, with the 

 mucous membrane; below, with the Mylohyoid muscle; in front, with the mandible 

 and its fellow of the opposite side; behind, with the deep part of the submaxillary 

 gland; and internally, with the Geniohyoglossus, from which it is separated by 

 the lingual nerve and submaxillary duct. Its excretory ducts or ducts of Rivinus 

 (ductus sublingualis minores) are from eight to twenty in number; some join the 

 submaxillary duct, others open separately into the mouth, on the elevated crest 

 of mucous membrane (plica sublingualis) caused by the projection of the gland 

 on either side of the frenum linguae. One or more join to form a tube which opens 

 into the submaxillary duct; this is called the duct of Bartholin (ductus sublingualis 

 major). 



Vessels and Nerves. The sublingual gland is supplied with blood from the sublingual and 

 submental arteries. Its nerves are derived from the lingual. 



Structure of Salivary Glands (Fig. 947). The salivary glands are compound tubulorace- 

 mose or racemose glands, surrounded by a capsule of white fibrous connective tissue that divides 

 the gland into numerous lobes and lobules. The tissue between the lobules supports blood- 

 vessels, nerves, lymphatics, and ducts. Each lobule consists of the ramifications of a single 

 duct, dividing frequently like the branches of a tree, the branches terminating in either rounded 

 or tubular ends, the acini or alveoli, around which the capillaries are distributed. Each alveolus 

 or acinus consists of a single layer of columnar or pyramidal epithelial cells resting upon a base- 

 ment membrane, further supported by the fibroelastic tunica propria, in which the capillaries and 

 nerves are found. Within the lobule are found intralobular ducts that collect the secretion 

 from the alveoli and empty it into the interlobular ducts between the lobules. The latter join, 

 to ultimately form the excretory duct of the gland. 



The main or excretory duct of each gland consists of mucous, muscle, and fibrous coats. 

 The mucous coat is composed of either simple columnar or stratified columnar epithelial cells 

 that rest upon a basement membrane, and . fibroelastic tunica propria. The muscle coat 

 consists of circularly arranged smooth muscle tissue. The fibrous coat consists of fibroelastic 

 tissue and serves to support the other coats. 



The salivary glands are mucous, serous, and mixed. The mucous glands secrete a thick 

 viscid fluid and the cells of the acini stain lightly. The alveoli are tubular in form and the cells 

 large and of a columnar shape, cloudy to transparent, and may even be striated in appearance. 

 At intervals peculiar, darkly staining crescent-shaped cells or cell groups are seen between the 

 above epithelium and the basement membrane; these are the demilunes of Heidenhain or 

 crescents of Gianuzzi (Fig. 947), by some regarded as mucous cells in the resting stage, and by 

 others as distinctly separate cells. ' These glands are the small unnamed glands of lips, cheek, 

 pharynx, oesophagus, and tongue (especially the glands of Nuhn and Blandin). 



