HUMAN STRUCTURE AND LIFE-ACTIVITIES 469 



390. The Esophagus or Gullet is a tube extending from 

 the pharynx to the stomach. In the human body, and in all 

 mammals, it extends through the 



diaphragm, the membrane which 

 divides the body-cavity into tho- 

 racic and abdominal portions. In 

 the neck the esophagus is behind 

 (dorsal to) the trachea. 



391. The Stomach is a muscular 

 and greatly expanded portion of 

 the alimentary canal or digestive 

 tube between the esophagus and Ll 

 the intestine. It lies on the left 

 side and in contact with the liver. 

 Imagine a membrane (diaphragm) 

 stretched across the frog's body- 

 cavity so as to separate the heart 

 and lungs from the stomach and 

 liver. The human diaphragm lies 



in the same position ; that is, the 

 heart and lungs lie above it (ante- 

 rior) and the stomach and liver lie 

 just beneath (posterior). The end 

 of the stomach connected with the 

 intestine is provided with a muscu- 

 lar ring (pylorus) which, by opening 

 and closing, is able to control the 

 passage of food from the stomach 

 to the intestine. It should be re- 

 membered that the size of a 

 stomach, like that of a rubber bag, 

 depends upon the amount of disten- 

 tion. When empty, it is contracted so that it has practi- 

 cally no cavity, and when much distended by food, it may 

 hold about a half-gallon. 



y 



FIG. 157. Human alimen- 

 tary organs. Gls, salivary 

 glands ; Ph, pharynx ; Gl. 

 th, thyroid gland ; Gl. thy, 

 thymus ; Lg, lung ; Oe, 

 esophagus ; Z, diaphragm ; 

 mg, stomach ; Pa, pancreas ; 

 Lb, liver ; Dd, small intes- 

 tine ; Vic, valve between 

 small and large intestine ; 

 Pv, appendix ; Ca, Ct, Cd, 

 colon of large intestine ; R, 

 rectum ; A, anus. (From 

 Wiedersheim.) 



