1242 



THE ORGANS OF DIGESTION 



The abdomen contains (Fig. 958) the greater part of the alimentary canal; 

 some of the accessory organs to digestion viz., the liver and pancreas; the spleen, 

 the kidneys, and adrenals, or suprarenal capsules. Most of these structures, 

 as well as the wall of the cavity 'in which they are contained, are covered by an 

 extensive and complicated serous membrane, the peritoneum (Fig. 988). 



The Apertures in the Walls of the Abdomen. The apertures found in the walls of 

 the abdomen, for the transmission of structures to or from it, are the umbilicus, for 

 the transmission (in the fetus) of the umbilical vessels; the caval opening in the 

 Diaphragm, for the transmission of the inferior vena cava; the aortic opening, 

 for the passage of the aorta, vena azygos major, and thoracic duct; and the 

 oesophageal opening, for the oesophagus and vagus nerves. Below, there are two 

 apertures on each side, one for the passage of the femoral vessels, and the other 

 for the transmission of the spermatic cord in the male, and the round ligament 

 in the female. 



Fio, 959. The regions of the abdomen and their contents. Edges of costal cartilages in dotted outline. 



Regions (Fig. 959). For convenience of description of the viscera, as well as 

 of reference to the morbid conditions of the contained parts, the abdomen is arti- 

 ficially divided into nine regions by imaginary planes, two horizontal and two 

 sagittal, passing through the cavity, the edges of the planes being indicated by 

 lines drawn on the ventral surface of the body. Of the horizontal planes, the upper 

 or infracostal is indicated by a line encircling the body at the level of the lowest 

 points of the tenth costal cartilages, the lower by a line carried around the trunk 

 at the level of the summits of the iliac crests. The lower plane closely corre- 

 sponds to the intertubercular plane passing through the trunk at the level of the 

 prominent and easily defined tubercle on the iliac crest about two inches behind 



