1164 



DIGESTIVE SYSTEM 



The end of the duodenum is firmly fixed in its place by the suspensorius duodeni. This 

 name has been given to a fibro-muscular band that contains, according to Treitz, non-striated 

 muscular fibres, and descends to the terminal part of the duodenum from the lumbar part 

 of the diaphragm, passing to the left of the coeliac artery and behind the pancreas. Lockwood 

 points out that this band is continued on, after being inserted into the duodenum, between 

 the layers of the mesentery. He suggests the name of the 'suspensory muscle of the duodenum 

 and mesentery,' and says, 'together with the other constituents of the root of the mesentery, 

 it forms a band of considerable strength, sufficient not only to support the weight of the intestines 

 and mesentery, but also to resist the pressure of the descent of the diaphragm.' 



In connection with this fourth portion of the duodenum, mention may be made of certain 

 peritoneal folds and fossae which are of some surgical interest by reason of their being associated 

 with retro-peritoneal hernia. Four such fossae may be mentioned, namely, the superior and in- 

 ferior duodenal fossae, paraduodenal and the retroduodenal fossae. On drawing the terminal 

 portions of the duodenum to the right, two triangular folds of peritoneum, the superior and in- 

 ferior duodenal folds, which extend from the wall of the duodenum to the posterior abdominal wall 

 may be observed. Each fold has a free edge. Beneath each fold is found a pouch of peri- 

 toneum, constituting the superior and inferior duodenal fossae. The former, the smaller, 

 opens do-^Tiward and is present in about 50 per cent., while the latter opens upward and is 

 present in about 75 per cent., of the subjects examined (Jonnesco). The paraduodenal fossa 

 (fossa of Landzert) is not often found in the adult; when present, it is situated to the left of the 

 last part of the duodenum, and is formed by a fold of peritoneum enclosing the inferior mesen- 

 teric vein. The retroduodenal fossa is a rare form extending from below^ upward behind the 

 transverse portion of the duodenum. 



Interior of the duodenum. — The interior of the first part of the duodenum 

 is smooth. The pylorus is often somewhat invaginated, much in the same way 

 that the uterus projects into the vagina (fig. 908). On account of this arrange- 



FiG. 923. — Duodenal Foss^ and Folds. Paraduodenal fossa is not shown. 



(After Cunningham.) 

 Transverse colon Transverse meso-colon 



Duodenum 



Superior duodenal fossa 



Inferior duodenal fossa 



The mesentery (cut) 



Inferior mesenteric vein 

 Inferior mesenteric artery 



ment (which renders the complete emptying of the cavity somewhat difficult) 

 and also on account of the distensibility of this portion, it usually shows up very 

 distinctly in radiographic pictures as a 'cap' to the pyloric end of the stomach 

 during digestion. In the lower portions of the duodenum, transverse ridges or 

 folds of the mucosa appear (fig, 922) which are also apparent in radiographs 

 occasionally. On the medial wall of the descending portion, posteriorly, about 

 half-way down, is a more or less distinct longitudinal fold [plica longitudinalis 

 duodeni], toward the lower end of which is a small elevation, the bile papillajor 

 papilla major [papilla duodeni], upon which open the common bile duct and the 

 pancreatic duct, either s(!parately or by a common aperture (fig. 922). Above 

 th(! papilla there is usually a prominent hood-like fold (valvula connivens), and 

 below it a variables fold or free nn in, which forms a continuation of the plica longi- 

 tudinalis. About 2 cm. (.9 to 3.5 cm., Jialdwin) above and in front of the bile 

 papilla there is a second, smaller, rounded papilla minor, upon which the ac- 

 cessory pancreatic duct (of Santorini) ends. 



The minute structure, vascular relations, development, variations, etc., of the duodenum 

 will be considered later, with tho.se of the small intestine as a whole. 



