The Digestive System 129 



coelom is known as the thoracic cavity and posteriorly as the abdom- 

 inal cavity. 



Although the digestive tract (Fig. 40) is essentially a tube, its 

 various parts are highly modified into separate organs. The most 

 anterior portion of the tract is the mouth. At the back of the mouth 

 is the pharynx which is a common passageway for both air and food. 



SUBMAXILLARY GLAND 



SUBUnCUAL SALIVARY 

 CLAND 



PAROTID 

 SALIVARY CLAMO 



BLADDER 



DUODEnUM 



HEPATIC 

 FLEXURE 



ASCEnDinC 

 COLON 



CECUM 



APPENDIX 



ILEUM 

 SICAAOID FLEXURE 



TRANSVERSE 

 ~ COLON 



DESCENDINC 

 COLON 



JEJUNUM 



SIGMOID 



RECTUM 



Fig. 40. — Th/e digestive tract of man. (From Zoethout and 

 Tuttle: Textbook of Physiology.) 



The pharynx leads directly into the esophagus, the only portion of 

 the tract in the thoracic cavity. The esophagus penetrates the dia- 

 phragm to join the stomach, a saclike organ separated from the small 

 intestine by a sphincter muscle. The much coiled small intestine is 

 the longest portion of the tract, and its coils occupy the greater part 



