944 THE ORGANS OF DIGESTIOX 



posterior surface, which is convex, is a coiitiimation of tlic floor of the nasal 

 cavity, and it forms a part of the anterior wall of tiie pharynx. 



Structure. — The soft palate is a fold of mucous meni])rane enclosing an 

 aponeurosis, muscles, vessels, and nerves. It is marked in the middle line b}' a 

 ra]ihe indicating the line of junction of the two halves from which it was formed. 



The posterior layer of the mucous fold which is directed towards the cavity of 

 the pharynx is continuous with the nasal niucous membrane; the anterior layer 

 lies in the posterior l)oundary of the mouth and is continuous with the mucous 

 membrane of the hard ])alate; the lower margin is free. Glands are numerous in 

 both layers, but more especially in the anterior. 



The ajioneurosis is attached above to the posterior margin of the hard ]ialate; 

 laterally it is continuous with the aponeurotic layer of the pharyngeal wall; below, 

 towards the lower margin of the soft palate, it gradually disappears, and it gives 

 attachment to fibres of the levator palati and the palato-pharyngeus and to the 

 tendon of the tensor palati. 



The muscles are arranged in layers either Ijehind or in front of the-aponeurosis, 

 and in a horizontal section of the soft palate the following layers are met with from 

 behind forwards: (1) The mucous membrane on the pharyngeal surface ; (2) the 

 posterior layer of palato-pharyngeus fibres ; (3) the azygos uvulae ; (4) the levator 

 palati ; (o) the anterior layer of ]ialato-]-)harvngeus fibres ; (6) the palatal aponeuro- 

 sis with the tensor palati ; (7) the palato-glossus ; and (8) the mucous membrane 

 on the buccal aspect. 



The Palato-Glossus is described on page 453. 



The Palato-Pharyngeus — named from its attachments — is a thin sheet. 



Origin. — (1 j From the aponeurosis of the soft palate by two heads which are 

 separated by the insertion of the levator palati; (2) one or two narrow bundles 

 from the lower part of the cartilage of the Eustachian tube {salpingo-'pharyngeus). 



Insertion. — (1) By a narrow fasciculus into the posterior border of the thj^roid 

 cartilage near the base of the superior cornu; (2) b}^ a broad expansion into the 

 fibrous layer of the pharynx at its loAver part. 



Structure. — The upper head of the muscle consists of scattered fibres which 

 l)lend with the opposite muscle across the middle line; the lower head is thicker, 

 and follows the curve of the posterior border of the palate. The two heads with 

 the fasciculus from the Eustachian tube form a compact muscular band in the 

 posterior pillar of the fauces; the fibres mingle with those of the stylo-pharyngeus, 

 at the lower border of the superior constrictor, and then expand upon the lower 

 part of the pharynx. 



Nerve-supply. — From the pharyngeal plexus. 



Action. — ( 1 ) Approximates the posterior pillars of the fauces; (2) depresses 

 the soft palate; (3) elevates the pharynx. 



The Levator Palati — named from its action on the soft palate — is somewhat 

 rounded in its upper, but flattened in its low^er half. 



Origin. — (1) The under surface of the petrosal anterior to the orifice of the 

 carotid canal; (2) the lower margin of the cartilage of the Eustachian tube. 



Insertion. — The aponeurosis of the soft palate; the terminal fibres of the 

 muscles of each side meet in the middle line in front of the azygos uvulff. 



Structure. — Its origin is l:)y a short tendon; the muscle then becomes fleshy, 

 and continues so to its insertion. 



Nerve-supply. — It is usual to describe this muscle as being innervated by the 

 facial through th(> petrosal l)ranch of the Vidian. The nerve is supposed to reach 

 the muscle through the small i)alatine nerve from Meckel's ganglion. Stimulation 

 of the facial trunk within the skull of monkeys produces no result on the soft 

 palate, whereas stimulation of the eleventh causes elevation of the soft palate on 

 the same side. The motor branch probably passes to the palate in the upper 

 branches of the pharyngeal plexus (Horsley and Beevor). 



Action. — (1) To raise up the palate, and bring it in contact with the posterior 

 wall of tlie pharynx; (2) when the nmscle contracts it presses up and closes the 

 pharyngeal orifice of the 'Eustachian tul)e (Cleland). This action is not admitted 

 by many anatomists. 



