1244 THE ORGANS OF DIGESTION 



viscera are in part exposed. Above and to the right side is the liver, situated 

 chiefly under the shelter of the right ribs and their cartilages, but extending across 

 the middle line, and reaching for some distance below the level of the ensiform 

 cartilage. To the left of the liver is the stomach, from the lower border of which 

 an apron-like fold of peritoneum, the greater omentum, descends for a varying 

 distance, and obscures, to a greater or less extent, the other viscera (Fig. 986). 

 Below it, however, some of the coils of the small intestine can generally be seen, 

 while in the right and left iliac regions respectively the cecum and the sigmoid 

 flexure of the colon are exposed. The bladder occupies the anterior part of the 

 pelvis, and, if distended, will project above the symphysis pubis; the rectum lies 

 in the concavity of the sacrum, but is usually obscured by the coils of the small 

 intestine. The sigmoid colon lies between the rectum and the bladder. 



If the stomach is followed from left to right it will be found to be continuous 

 with the first part of the small intestine, or duodenum, the point of continuity 

 being marked by a thickened ring which indicates the position of the pyloric 

 sphincter. The duodenum passes toward the under surface of the liver, and then, 

 curving downward, is lost to sight. If, however, the great omentum be thrown 

 upward over the thorax, the terminal part of the duodenum will be observed 

 passing across the vertebral column toward the left side, where it becomes con- 

 tinuous with the coils of the small intestine. These measure some twenty feet in 

 length, and if followed downward will be seen to end in the right iliac fossa by 

 opening into the cecum, the commencement of the large intestine. From the 

 cecum the large intestine takes an arched course, passing at first upward on the 

 right side, then across the middle line and downward on the left side, and forming 

 respectively the ascending, transverse, and descending parts of the colon. In the 

 left iliac region it assumes the form of a loop, the sigmoid flexure, then follows the 

 curve of the sacrum and terminates in the rectum and anal canal. 



The spleen lies behind the stomach in the left hypochondriac region, and may 

 be in part exposed by pulling the stomach over toward the right side. 



The glistening appearance of the deep surface of the abdominal wall and of 

 the exposed viscera is due to the fact that the former is lined and the latter more 

 or less completely covered by a serous membrane, the peritoneum. 



THE PERITONEUM (TUNICA SEROSA). 



The peritoneum is the largest serous membrane in the body, and consists, in 

 the male, of a closed sac, a part of which is applied against the abdominal parietes, 

 while the remainder is reflected more or less completely over the contained viscera. 

 In the female the peritoneum is not a closed sac, since the, free extremities of the 

 Fallopian tubes open_directl^Jnto the peritoneal cavity. ^The part which linesTKe* 

 pafieles is named the parietal peritoneum; that which "is reflected over the viscera, 

 the visceral peritoneum. The free surface of the membrane is smooth, covered by a 

 layer of flattened endothelium, and lubricated by a small quantity of serous fluid. 

 Hence the viscera can glide freely against the wall of the cavity or upon one another 

 with the least possible amount of friction. The attached surface is rough, being 

 connected to the viscera and inner surface of the parietes by means of areolar 

 tissue termed the subserous areolar tissue (tela subserosa). The parietal portion 

 is loosely connected with the fascia lining the abdomen and pelvis, but more 

 closely to the under surface of the Diaphragm and also in the middle line of the 

 abdomen. 



The space between the parietal and visceral layers of the peritoneum is named 

 the peritoneal cavity; but it must be remembered that under normal conditions this 

 cavity is a potential one, since the parietal and visceral layers are in contact. 



