98 PRACTICAL ANATOMY. 



covering the same. This comes from the fifth cranial nerve, through dental and 

 gingival branches respectively. 



2. Nerve-supply, motor, to the muscles that elevate the jaw, and sensory, to 

 the skin covering these muscles. This is from the fifth cranial nerve. 



3. Nerve-supply, sensory, to the articulation moved by the muscles of 

 mastication the temporo-mandibular articulation. This is from the auriculo- 

 temporal branch of the fifth cranial nerve. This is explained by Hilton's law. 



4. Nerve-supply, sensory, to the roof of the mouth. This is from the fifth 

 through Meckel's ganglion. Also the sensory nerve-supply to the tongue. 

 The greater part of this is from the fifth nerve through the lingual branch. 



5. Nerve-supply to the inner nose, or that part of the system that selects 

 food by the sense of smell. The sensory part of this is in great part from the 

 fifth nerve, through Meckel's ganglion. The special sense of smell is from the 

 olfactory or first cranial nerve. 



6. Nerve-supply concerned in deglutition. Here a separate system, the 

 digestive, begins, as is evidenced by a radical change in the nerve-supply. The 

 muscles of the soft palate and pharynx are supplied by the pharyngeal plexus, 

 the principal factors in which are the sympathetic and vagus nerves ; these 

 nerves supply all the other organs of the digestive tract. 



What is the salivary system ? 



This system consists of the salivary glands, the parotid, the submaxillary, 

 the sublingual, and their capsules, their nerve-supply, principally sympathetic, 

 and their blood-supply. The latter is derived from the main artery of the 

 region in which the glands are found. 



THE SOFT PALATE. 



1. Prevents rcgurgitation of food into the mouth. (Fig. 64.) 



2. Prevents passage of ingesta into the posterior nares. 

 The structures concerned are the following : 



1. The palato-glossus muscle. Nerve-supply, pharyngeal plexus. 



2. The palato-pharyngeus muscle. Nerve-supply, pharyngeal plexus. 



3. The levator palati muscle. Nerve-supply, pharyngeal plexus. 



4. The tensor palati muscle. Nerve-supply, otic ganglion. 



5. The azygos uvulae. Nerve-supply, pharyngeal plexus. 



To see the action of the palato-glossus muscle on the living subject, make 

 prolonged effort to depress the tongue. When the patient is on the verge ot 

 nausea, you will see the anterior pillars of the fauces spread out and draw the 

 tongue closely under the palatine arch. This is, then, their action : during 

 swallowing, after the bolus passes the initial part of the faucial passage, the 

 tongue is forced under this arch to prevent regurgitation, while the constrictors 

 of the pharynx are contracting on the food. During the same act the palato- 

 pharyngei spread in such a way as to protect the upper pharynx and posterior 

 nares, acting with the levator palati ; the circumflexus tightens the soft palate. 



The levator palati (Fig. 65) arises from the cartilage of the Eustachian tube, 

 and from the under surface of the petrous portion of the temporal bone. It is 

 inserted into the soft palate near the mid-line. 



The circumflexus (Fig. 65), or tensor palati, arises from the scaphoid fossa 

 of the sphenoid bone. (Fig. i i.) The tendon passes around the hamular pro- 

 cess of the internal pterygoid plate and is inserted into the median rap he of the 

 soli palate. Some of its fibres are also inserted into the posterior margin of the 

 hard palate. 



The azygos uvulae (Fig. 65) consists of some muscular fibres extending 

 from the posterior nasal spine to the end of the a/ygos uvulae. (Fig. 1 1.) 



