THE CESOPHAGUS. 



'55 



uous ill the lower portion Collections of lymphoid tissue occur within the 

 mucosa as more or less distinct aggregations. Mostly they are small diffuse 

 areas around the ducts of the mucous glands, but in some places, especially 

 towards the lower end of the oesophagus, they assume the form of distinct 

 lymph-nodules (Fig. 195). 



The submucous layer, although of considerable thickness, is loose in 

 texture and, therefore, permits free motion of the mucous membrane upon 

 the muscular tunic. Scattered along the length of the gullet are many 



Epithelium 



Tunica propria of 



mucous membrane 



Muscularis 

 mucosae 



Circular 

 nonstriated muscle 



Longitudinal 

 nonstriated muscle 



FIG. 194. Transverse section of oesophagus, through upper third. X 18. 



cesophageal glands. These are of two kinds the ordinary mucous 

 glands, situated within the submucous coat and most abundant in the upper 

 half of the tube, and the special cardiac glands, lodged within the tunica 

 propria and limited to the two ends of the oesophagus. The usual glands 

 are tubo-alveolar in form and pure mucous in type, mucus-producing cells 

 alone being present. Their ducts, commonly somewhat tortuous, are often 

 dilated into miniature ampullae just before penetrating the muscularis 

 mucosas; they leave the tunica propria and enter the epithelium in the val- 

 leys between the papillae. The smaller ducts are lined with simple columnar 

 epithelium, which in the larger tubes may become stratified and, near the 

 free surface, may be replaced by stratified squamous cells. 



The special glands correspond in structure to those found at the cardiac 

 orifice of the stomach (page 160); hence their designation as "cardiac." 

 They consist of small oval or pyramidal groups of richly branched tubules 



