274 



THE DIGESTIVE SYSTEM 



THE MUSCULAR COAT contains an outer longitudinal and 

 an inner circular layer of muscle fibres, which are separated by a 

 narrow septum of loose fibrous tissue. In the upper and middle 

 thirds of the esophagus the muscle is of 'the striated variety, in 



FIG. 227. FROM A LONGITUDINAL SECTION AT THE JUNCTION OF THE MIDDLE AND 



LOWER THIRD OF THE HUMAN ESOPHAGUS. 



a, epithelium; 6, corium, and c, muscular layer of the mucosa; d, fibrous tissue, and 

 e, mucous glands of the submucosa : y, inner, and ^, outer layer of the muscular coat, 

 the former partly of smooth and partly of striated fibres ; A, edge of the outer fibrous 

 coat. Hematein and eosin. Photo, x 42. 



the lower third it is largely smooth or involuntary muscle. The 

 distribution of the muscle in the lower third is, however, subject 

 to great individual variation, and occasional striated fibres are 

 often found all the way down to the diaphragmatic opening. 



