THE PHARYNX AND OESOPHAGUS. 



101 



Fig. 82. 



The superior constrictor muscle ' is quadrilateral, and arising from 

 the pterygoid process of the sphenoid bone, from the upper and lower 

 jaw, the buccinator muscles, and the root of the tongye ; is inserted 

 into its fellow behind, and also into the basilar process of the occiput. 



The stylo-pharyngeus iniiscle^'^ has been described before. 



The cellular coat is thin, and merely serves for a transmission of 

 vessels and nerves, and the connexion of the external and internal 

 coats. 



The internal or mucous coat is a 

 continuation of that of the mouth, 

 nose, and Eustachian tube, and it is 

 covered by a thin epithelium, and 

 studded with mucous follicles and 

 glands. It is supplied by the pha- 

 ryngeal and palatine arteries, and by 

 the sympathetic, and eighth pair of 

 nerves. Its uses are for deglutition, 

 respiration, and modulation of the 

 voice. 



The (Esophagus is a canal which 

 conveys the food from the pharynx 

 to the stomach. It is situated in the 

 median line, in front of the vertebral 

 column, and passing through the 

 posterior mediastinum, and inclin- 

 ed somewhat to the left side in its 

 lower part, where it passes through 

 the diaphragm. Its length is about 



nine or ten inches, and its diameter is not uniform, gradually in- 

 creasing as it descends. Its upper portion is the narrowest part of 

 the alimentary canal, and hence foreign bodies which are too large 

 to pass through the alimentary canal, are generally arrested in the 

 neck ; its shape is cylindrical, although its walls when at rest, are 

 in contact, never containing air. It consists of three coats, the ex- 

 ternal of which is muscular, and thicker than any other portion of 

 the canal; it consists of two layers, the 62;^e/-W(2^ consists. of longi- 

 tudinal fibres, and the internal of circular fibres. The cellular coat- 

 attaches the muscular and mucous, and serves for the passage of 

 vessels and nerves. The internal or mucous coat is continuous 

 with that of the pharynx, and has a number of longitudinal folds 

 when in a state of quiet. It has a thick epithelium, and numerous 

 mucous glands and follicles. It is supplied by the cesophageal ar- 

 teries, proceeding from the inferior thyroid, aorta, coronary, and 

 phrenic arteries ; its nerves are derived from the eighth pair, and' 

 from the sympathetic. 



Deglutition is performed by the contraction of its longitudinal 



9* 



