944 THE ORGANS OF DIGESTION. 



THE PALATE. 



The palate forms the roof of the mouth : it consists of two portions, the hard 

 palate in front, the soft palate behind. 



The hard palate is bounded in front and at the sides by the alveolar arches 

 and gums ; behind, it is continuous with the soft palate. It is covered by a dense 

 structure formed by the periosteum and mucous membrane of the mouth, which 

 are intimately adherent together. Along the middle line is a linear ridge or 

 raphe, which terminates anteriorly in a small papilla (incisive pad) correspond- 

 ing with the inferior opening of the anterior palatine fossa. This papilla 

 receives filaments from the naso-palatine and anterior palatine nerves. On either 

 side and in front of the raphe the mucous membrane is thick, pale in color, and 

 corrugated ; behind, it is thin, smooth, and of a deeper color : it is covered with 

 squamous epithelium, and furnished with numerous glands (palatal glands), 

 which lie between the mucous membrane and the surface of the bone. 



The soft palate (velum pendulum palati) 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 

 muscular fibres, an aponeurosis, vessels, nerves, adenoid tissue, and mucous 

 glands. When occupying its usual position (i. e. relaxed and pendent) its anterior 

 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 posterior surface is convex, and continuous with the mucous 

 membrane covering the floor of the posterior nares. Its upper border is attached 

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

 pharynx. Its lower border is free. 



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

 pendulous process, the uvula, and arching outward and downward from the base 

 of the uvula on each side are two curved folds of mucous membrane, containing 

 muscular fibres, called the arches or pillars of the soft palate. 



The anterior pillars run downward, outward, and forward to the sides of the 

 base of the tongue, and are formed by the projection of the Palato-glossi muscles, 

 covered by mucous membrane. 



The posterior pillars are nearer to each other and larger than the anterior ; they 

 run downward, outward, and backward to the sides of the pharynx, and are 

 formed by the projection of the Palato-pharyngei muscles, covered by mucous 

 membrane. The anterior and posterior pillars are separated below by a triangular 

 interval in which the tonsil is lodged. 



The space left between the arches of the palate on the two sides is called the 

 isthmus of the fauces. 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 soft 

 palate and the tonsil. 



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

 epithelium on its under surface, while on its superior surface the epithelium 

 is columnar and ciliated. 1 Beneath the mucous membrane on the oral surface 

 of the soft palate is a considerable amount of adenoid tissue. The palatine glands 

 form a continuous layer on its posterior surface and round the uvula. 



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

 to the posterior border of the hard palate, and becoming thinner toward the free 

 margin of the velum. Laterally, it is continuous with the pharyngeal aponeurosis. 

 It forms the framework of the soft palate, and is joined by the tendon of the Tensor 

 palati muscle. 



The muscles of the soft palate are five on each side : the Levator palati, 

 Tensor palati, Azygos uvulae, Palato-glos'sus, and Palato-pharyngeus (see page 421). 

 The following is the relative position of these structures in a dissection of the soft 



1 According to Klein, the mucous membrane on the nasal surface of the soft palate is in the 

 foetus covered throughout by columnar ciliated epithelium, which subsequently becomes squamous. 



