1154 THE DIGESTIVE SYSTEM. 



order to allow of the expansion of the tube during swallowing. It connects the mucous 



Longitudinal 

 fibres diverging 



Trachea 



FIG. 909. DISSECTION to show the 

 arrangement of the muscular fibres on 

 the posterior aspect of the oesophagus 

 and pharynx. Traced upwards, the 

 longitudinal muscular fibres of the oeso- 

 phagus are seen to separate posteriorly ; 

 passing round to the sides, they form 

 two longitudinal bands which meet 

 anteriorly and are united to the cricoid 

 cartilage, as shown in the next figure. 



Upper border of 

 cricoid cartilage 



Tendinous band 



Circular fibres 

 'of O3sophagus 



Longitudinal bands 



FIG. 910. THE INFERIOR PART OP THE PHARYNX 

 AND THE SUPERIOR PART OF THE (ESOPHAGUS have 

 been slit up from behind, and the mucous mem- 

 brane removed to show the muscular fibres. The 

 two longitudinal bands are seen passing round 

 to the front to be attached by a common tendon 

 to the superior border of the cricoid cartilage. See 

 explanation of last figure. 



Epithelium | Tunica 

 Papilla jmucosa 



Conn, tissue 



Lamina 



muscularis 



mucosae 



Loose conn. 



tissue 



Glandula 



Tela 

 subinucosa 



membrane loosely to the muscular coat, and admits of the former being thrown into folds 



when empty. In thL< 

 coat are contained th( 

 numerous racemose 

 mucous glands (glandula 

 oesophagese) which opei 

 into the cavity of th< 

 oesophagus (Fig. 911). 



The tunica mucos* 

 is of 'a grayish-pinl 

 colour, much paler thai 

 that of the pharynx 

 and of a firm and resis 

 tant texture. It i 

 covered with a thicl 

 stratified, squamous epi 

 thelium, on the surfac 

 of which the opening 

 of numerous glands ar 

 found. Inferiorly, it 

 junction with the gastri 

 mucous membrane i 

 indicated by a distinc 

 irregularly dentated c 

 crenated line, which rur 

 transversely round th 

 tube. In carefully pr 

 oesophagus above this In 



Tunica 

 muscularis 



FIG. 911. TRANSVERSE SECTION OF WALL OF HUMAN (ESOPHAGUS. 



served specimens the smooth mucous membrane of the 



contrasts strongly with the mamillated gastric mucous membrane below. 



Owing to the inelasticity of this coat, and the fact that it is but loosely connected 



