1240 



A MANUAL OF ANATOMY 



Annexed to the stomodgeum there are (i ) the pouch of Rathke, (2) the tongue 

 (3) the saUvary glands, (4) the tonsils, and (5) the teeth. 



The pouch ol Rathke is an evagination or diverticulum of the roof of the 

 ectodermic stomodaeum, ventral to the bucco-pharyngeal membrane. It 

 grows in a cephalic direction, and gives rise to the anterior lobe ol the pituitary 

 body, or hypophysis cerebri, the posterior lobe of which is developed from a 

 diverticulum of the floor of the third ventricle of the cerebrum. 



The development of the tongue, salivary glands, tonsils, and teeth will be 

 found after the description of each of these organs. 



The stomodceum becomes divided into two chambers — upper or nasal and 

 lower or oral — this division being effected by the formation of the hard 

 palate. The nasal chamber becomes transformed into the two nasal fossae, 

 and the oral chamber constitutes the oral cavity or permanent mouth. 



The permanent oral cavity is much more circumscribed than the primitive 

 oral cavity or stomodaeum. The latter, as already stated, includes the cephalic 

 part of the pharynx, but that part of the pharynx is, in adult life, shut off 

 from the permanent oral cavity by the velum pendulum palati or soft palate. 



The development of the hard palate is described in connection with the 

 visceral arch skeleton of the face, but it may be here briefly restated. 



Globular Process . 



Maxillary Palatal Process 

 Maxillary Process 



Oral Cavity 



Palatal Processes of Globular Processes 

 t 



Aperture of Olfactory Pit 



Lens 

 . Eye 



Palatal Shelf 



Pouch of Rathke 



Fig. 504 — Roof of Mouth (Marshall, after His). 



The horizontal or palatal plate of the palate bone and the greater part of 

 the palatal plate of the superior maxilla, of either side, are developed from the 

 palatal shelf of the corresponding maxillary process of the first visceral, or 

 mandibular, arch. The incisor or premaxillary portion of the psJatal plate 

 of the superior maxilla — that is to say, the portion ventral to the incisor or 

 premaxillary suture on the under aspect — is developed, on either side, from 

 the nasal lamina of the corresponding globular process of the mesial nasal 

 process of the fronto-nasal process. The formation of the hard palate is 

 completed about the end of the third month. 



Lips [labia oris) and Gums [gingiva;). — Shortly after the fusion of the max- 

 illary and globular processes to form the superior maxilla, a groove, produced 

 by an ingrowth of epithelium, appears along each of these processes, on either 

 side. The margins of this groove, which form parallel ridges, are external 

 and internal, relatively to the oral cavity. The external, or labial, ridge gives 

 rise to the upper lip, the globular portion of the ridge representing the pre- 

 maxillary part of the lip, and the maxillary portion forming the remainder. 

 The internal or gingival ridge is the rudiment of the upper gum. 



The philtrum is probably developed from the mesodermic investment of 

 the united globular processes. 



A similar groove and similar ridges [labial and gingival) appear along each 

 mandibular arch, and from the ridges the lower lip and lower gum are developed. 



The angles of the mouth correspond to the union between the two lips, 

 on either side, and each originally represents the angle between a mandibular 

 arch and maxillary process. 



