:i86 



A MANUAL OF ANATOMY 



glands, having previously traversed the parotid lymphatic glands, 

 and, in the case of some, the submaxillary lymphatic glands. 



Nerve-supply. — (i) The auriculo- temporal nerve, which conveys to 

 the gland secretory fibres of the glosso-pharyngeal nerve through its 

 tympanic branch (Jacobson's nerve), 

 the small superficial petrosal nerve, 

 and the otic ganglion ; (2) the great 

 auricular nerve ; (3) the sympathetic 



plexus on the external carotid artery ; ^/^^^^Ig^fr^^l^M^e^^ 

 and (4) the facial nerve. ^t^^^^v^^^^y^^^^^^ 



Fig. 



482. — Structure of the 

 Parotid Gland. 



Structure. — The parotid gland is a com- 

 pound racemose or acino-tubular gland, and 

 is composed of large lobules, which are 

 united by connective tissue. Each of these 

 is made up of smaller lobules, likewise con- 

 nected by connective tissue. Each small 

 lobule is a gland on a minute scale, and is 

 made up of a group of more or less saccu- 

 lated tubules, called alveoli or acini. A 

 duct passes from each small lobule, which 



unites with adjacent ducts, and these in turn unite, larger and still larger 

 • ducts being formed, the resultant being the principal duct, called Stensen's 

 duct. Each alveolus is serous or albuminous as regards the nature of its 

 secretion, and is composed of a basement membrane continuous with the wall 

 of the duct, and surrounded by a plexus of capillaries. The alveolus is lined 

 with polyhedral cells, which contain albuminous granules, and almost com- 

 pletely fill the tube, leaving only a small lumen. The first portion of the 

 duct, called the intercalary duct, is lined with flattened epithelium. Beyond 

 this the duct becomes constricted into a neck, which is lined with cubical cells, 

 these being replaced in the intralobular duct by columnar cells. These cells 

 are granular towards the lumen of the tube, but striated in the outer part. 

 Each of the larger ducts is composed of a basement membrane, strengthened 

 externally by a layer of connective tissue, superadded to which there is a 

 stratum of plain muscular fibres. 



Development 0! the Salivary Glands. — ^The salivary glands — parotid, sub- 

 maxillary, and sublingual — are of ectodermic origin. They appear as solid 

 outgrowths of the epithelium of the stomodaeum, or primitive buccal cavity, 

 which grow into the adjacent mesodermic connective tissue. The epithelial 

 constituents of each gland are derived from the stomodaal ectoderm, whilst 

 the capsule and connective-tissue elements are of mesodermic origin. 



Each solid epithelial outgrowth ramifies very freely, and these ramifications, 

 as well as the primary outgrowth, become tubular. The hollowing process 

 commences in the primary outgrowth, and extends thence throughout its 

 numerous ramifications. The primary outgrowth represents the principal 

 duct of each gland, and the acini, or alveoli, appear as dilatations of the walls 

 of the terminal ramifications. 



The sublingual gland, from its numerous ducts, is to be regarded as a cluster 

 of small alveolo-lingual glands. A few of these glands are developed from 

 diverticula of Wharton's duct, which is the duct of the submaxillary gland. 

 The majority of them, however, like the parotid and submaxillary glands, 

 are developed from solid epithelial outgrowths of the ectoderm of the stomo- 

 daeum. 



