902 THE ORGANS OF DIGESTION. 



covering respectively the anterior and posterior surfaces of the stomach. When 

 these two layers reach the lesser curvature of the stomach, they join together and 

 ascend as the double fold to the transverse fissure of the liver ; to the left of this 

 fissure the double fold is attached to the fissure of the ductus venosus as far as the 

 Diaphragm, where the two layers separate to embrace the end of the oesophagus. 

 At the right border the lesser omentum is free, and the two layers of which it is 

 composed are continuous. The anterior layer, which belongs to the greater sac, 

 turns round the hepatic vessels to become continuous with the posterior layer be- 

 longing to the lesser one. They here form a free, rounded margin, which contains 

 between its layers the hepatic artery, the common bile-duct, the portal vein, 

 lymphatics, and the hepatic plexus of nerves all these structures being enclosed in 

 loose areolar tissue, called Glissoris capsule. Between the layers where they are 

 attached to the stomach lie the gastric artery and the pyloric branch of the hepatic, 

 anastomosing with it. 



The great omentum (g astro-colic) is the largest peritoneal fold. It consists of 

 four layers of peritoneum, two of which descend from the stomach, one from its 

 anterior, the other from its posterior surface, and, uniting at its lower border, 

 descend in front of the small intestines, sometimes as low down as the pelvis ; 

 they then turn upon themselves, and ascend again as far as the transverse colon, 

 where they separate and enclose that part of the intestine. These separate layers 

 may be easily demonstrated in the young subject, but in the adult they are more 

 or less inseparably blended. The left border of the great omentum is continuous 

 with the gastro-splenic omentum : its right border extends as far only as the 

 duodenum. The great omentum is usually thin, presents a cribriform appearance, 

 and always contains some adipose tissue, which in fat subjects accumulates in 

 considerable quantity. Its use appears to be to protect the intestines from the 

 cold, and to facilitate their movement upon each other during their vermicular 

 action. Between its two anterior layers is the anastomosis between the right and 

 left gastro-epiploic arteries. 



The gastro-splenic omentum is the fold which connects the margins of the 

 hilum of the spleen to the cul-de-sac of the stomach, being continuous by its lower 

 border with the great omentum. It contains the vasa brevia vessels. 



The Mesenteries are : the mesentery proper, the transverse mesocolon, the 

 sigmoid mesocolon, and the mesorectum. In addition to these there are some- 

 times present an ascending and a descending mesocolon. 



The mesentery (fjisffov Hvrepov), so called from being connected to the middle 

 of the cylinder of the small intestine, is the broad fold of peritoneum which 

 connects the convolutions of the jejunum and ileum with the posterior wall of 

 the abdomen. Its root, the part connected with the vertebral column, is narrow, 

 about six inches in length, and directed obliquely from the left side of the second 

 lumbar vertebra to the right sacro-iliac symphysis (Fig. 490). Its intestinal 

 border is much longer ; and here its two layers separate so as to enclose the 

 intestine, and form its peritoneal coat. Its breadth, between its vertebral and 

 intestinal border, is about eight inches. Its upper border is continuous with the 

 under surface of the transverse mesocolon : its lower border, with the peritoneum 

 covering the caecum and ascending colon. It serves to retain the small intestines 

 in their position, and contains between its layers the mesenteric vessels and 

 nerves, the lacteal vessels, and mesenteric glands. 



In most cases the peritoneum covers only the front and sides of the ascending 

 and descending parts of the colon. Sometimes, however, these are surrounded 

 by the serous membrane and attached to the posterior abdominal wall by an 

 ascending and a descending mesocolon respectively. At the place where the 

 transverse colon turns downwards to form the descending colon, a fold of perito- 

 neum is continued to the under surface of the Diaphragm opposite the tenth and 

 eleventh ribs. This is the phreno-colic ligament ; it passes below the spleen, and 

 serves to support this organ, and therefore it has received the second name of 

 sustentaculum lienis. 



