THE MOUTH, ORAL OR BUCCAL CAVITY 1205 



The Soft Palate (palatum molle) (Figs. 914 and 915) is a movable fold suspended 

 from the posterior border of the hard palate, and forming an incomplete septum 

 between the mouth and pharynx. It consists of a fold of mucous membrane 

 enclosing muscle fibres, an aponeurosis, vessels, nerves, lymphoid tissue, and 

 mucous glands. When occupying its usual position it is relaxed and pendent, 

 and its oral surface is concave, continuous with the roof of the mouth, and marked 

 by a median ridge or raphe', which indicates its original separation into two lateral 

 halves. Its pharyngeal surface is convex, and continuous with the mucous mem- 

 brane covering the floor of the posterior nares. Its anterior or upper border is 

 attached to the posterior margin of the hard palate, and its sides are blended with 

 the pharynx. Its posterior or lower border is free. The posterior portion of the 

 soft palate (velum palatinwri) terminates posteriorly and externally on each side 

 in a free margin, the posterior arch of the palate, and bounds the isthmus of the 

 pharynx. 



Hanging from the middle of its lower border is a small, cone-shaped, pen- 

 dulous process, the uvula (uvula palatina). The uvula varies greatly in length in 

 different individuals. It is composed of glands and connective tissue, contains 

 a prolongation of the Azygos uvulae muscle and is covered with mucous membrane, 

 and arching outward and downward from the base of the uvula on each side are 

 two curved folds of mucous membrane, containing muscle fibres, called the 

 arches or pillars of the soft palate or pillars of the fauces (arcus palatini). 



The anterior pillar (arcus glossopalatinus) (Fig. 914) on each side runs downward, 

 outward, and forward to the side of the base of the tongue, and is formed by the 

 projection of the Palatoglossus muscle, covered by mucous membrane. 



The posterior pillar (arcus pharyngopalatinus) (Fig. 914) is larger and projects 

 farther inward than the anterior; it runs downward, outward, and backward 

 to the sides of the pharynx, and is formed by the projection of the Palatopharyngeus 

 muscle, covered by mucous membrane. The anterior and posterior pillars are 

 separated below by a triangular interval (tonsillar sinus), in which the tonsil 

 is lodged. 



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

 isthmus of the fauces (isthmus faucium). It is bounded, above, by the free margin 

 of the soft palate; below, by the back of the tongue; and on each side, by the 

 pillars of the fauces and the tonsils. 



The aponeurosis of the soft palate is a thin but firm fibrous layer attached above to the pos- 

 terior border of the hard palate, and becoming thinner toward the free margin of the soft palate. 

 Laterally, it is continuous with the pharyngeal aponeurosis. It forms the framework of the 

 anterior half of the soft palate, and is joined by the tendons of the Tensor palati muscles. 



The muscles of the soft palate are found in its posterior half, and are six on each side the 

 Levator palati, Tensor palati, Azygos uvulae, Palatoglossus, Palatopharyngeus, and Sal- 

 pingopharyngeus (see p. 398). The following is the relative position of these structures in a 

 dissection of the soft palate from the posterior or nasopharyngeal to the anterior or oral surface: 

 Immediately beneath the pharyngeal mucous membrane is a thin stratum of muscle tissue, the 

 posterior fasciculus of the Palatopharyngeus muscle, joining with its fellow of the opposite side 

 in the middle line. This posterior fasciculus is joined by the Salpingopharyngeus muscle. 

 Beneath this are the Azygos uvulae and Salpingopharyngeus muscles, consisting of two rounded 

 fleshy fasciculi, placed side by side in the median line of the soft palate. Next comes the apo- 

 neurosis of the Levator palati, joining with the muscle of the opposite side in the middle line. 

 Fourthly, the anterior fasciculus of the Palatopharyngeus, thicker than the posterior, and sepa- 

 rating the Levator palati from the next muscle, the Tensor palati. This muscle terminates in a 

 tendon which, after winding around the hamular process of the internal pterygoid plate of the 

 sphenoid bone, expands into a broad aponeurosis in the soft palate, anterior to the other muscles 

 so far enumerated. Finally, we have a thin muscular stratum, the Palatoglossus muscle, placed 

 in front of the aponeurosis of the Tensor palati, and separated from the.oral mucous membrane by 

 lymphoid tissue. 



The mucous membrane of the soft palate is thin, and covered with stratified squamous epi- 

 thelium on both surfaces, excepting near the orifice of the Eustachian tube, where its epithelium 



