1110 



THE DIGESTIVE SYSTEM. 



developed in the child than in the adult, strengthens the cheek, and helps it to resist the effects 

 of atmospheric pressure during the act of sucking. In the adult the remains of the pad can be 

 distinctly made out under the anterior border of the masseter. 



Some small superficial lymph -glands lie on the superficial surface of the buccinator, com- 

 municating with the vessels of the lips, while their efferent vessels pass onwards towards the 

 parotid region. 



Palatum. The palate forms the roof of the mouth, and separates the mouth 

 from the nasal cavities and nasal part of the pharynx. 



It is not confined to the mouth, but extends backwards also into the cavity of 

 the pharynx, forming the division between the oral and the nasal parts of the 

 pharynx. It terminates behind in a free conical projection, the uvula. It consists 

 of two distinct portions, an anterior, forming the anterior two-thirds, which has a 

 bony foundation (palatine processes of the maxillse and the horizontal parts of the 

 palatine bones), and a posterior, forming the posterior third, with a fibrous basis ; and 

 they are termed the hard and the soft palate, respectively. The palate is arched 

 antero-posteriorly, and also transversely. The latter curvature is the more pro- 

 nounced in the hard palate, but the shape and curvature of this portion depend 

 upon the configuration of its bony foundation. 



The hard palate is, on the whole, horizontal in direction, both transversely and antero- 

 posteriorly. The soft palate is, on the other hand, during rest, as, for instance, in quiet nasal 

 breathing, very oblique in direction, and it shuts off the mouth from the nasal and largely from 

 the oral parts of the pharynx. When, however, the soft palate is raised by the action of its 

 muscles, it more nearly continues backwards the plane of the hard palate, and it projects across 

 the cavity of the pharynx, forming a nearly complete partition between the oral and the nasal 

 parts of the pharynx. In this position it prevents food from passing upwards into the nasal 

 part of the pharynx and nose. 



Traversing the middle of the palate is seen a faint median ridge or raphe (Fig. 877), indicating 

 its original development from two halves. This raphe is continued posteriorly along the soft 

 palate to the base of the uvula, and in front it ends in a slight elevation, the papilla palatina 

 (O.T. incisive pad). From the anterior end of the raphe a series of transverse ridges of mucous 

 membrane, about six in number, run laterally, just behind the incisor teeth ; they are known as 

 the plicae palatinae, and are composed of dense fibrous tissue. Sometimes a small pit, which will 

 admit the point of a pin, is seen, on each side, immediately posterior to the central incisor teeth, 

 and about 2 mm. from the median plane. These pits correspond to the inferior openings of 

 the incisive canals, with which they are occasionally continuous. 



Palatum Durum. The hard palate consists of a horizontal plate formed by 

 the palatine processes of the maxillae and the horizontal parts of the palatine bones, 



covered on each surf ace, super- 

 Foramen incisi vum / -4^. Dentes incisivi j or an( j inferior, by periosteum. 



The periosteum of the inferior 

 surface is thick, and is in 

 turn covered by a quantity of 

 dense fibrous tissue firmly 

 united both to the periosteum 

 and to the mucous mem- 

 brane. This dense tissue 

 contains in its posterior half 

 a large number of racemose 

 palatine glands, and it also 

 contains the larger nerves 

 and blood-vessels of the 

 palate. The mucous mem- 

 brane covering the superior 

 surface is largely ciliated in 

 character, and forms the floor 

 of the nasal cavity, while that 

 on the inferior surface is e 

 stratified squamous epi- 

 thelium. 



Palatum Molle. The soft palate is attached anteriorly to the posterior margii 

 of the hard palate. Its lower and posterior margin is free, and forms an arch, e 

 tending from one side of the pharynx to the other, but the arch is interruptec 



)ens caniims 



Denies prsemolares 



w 



Foramen 

 paiatinuin majus 



Sutura palatina transversa 



FIG. 877. THE HARD PALATE AND UPPER PERMANENT TEETH, 

 SEEN FROM BELOW. 



