1376 CLINICAL AND TOPOGRAPHICAL ANATOMY 



The duodeno- jejunal flexure, which lies on the left side of the body of the second lumbar 

 vertebra, immediately below the body of the pancreas, is held up to the right crus of the dia- 

 phi-agm by a band of fibro-muscular tissue known as the suspenaorij ligament of Treitz. Some of 

 the fibres of this structm-e are continued onward into the root of the mesentery. It is not found 

 in pronograde animals. The duodeno-jejunal flexure is the commonest site of traumatic rup- 

 ture of the small intestine, since it is the point of union of a fixed and a freely movable portion 

 of the gut. 



In the operation of posterior gastro-enterostomy the duodeno-jejunal flexure is readily 

 found by passing the hand along the under sm-face of the transverse meso-colon to the left side 

 of the spine, the omentum and colon being turned upward. The first coil of the jejunum is 

 anastomosed to the posterior wall of the stomach, which is exposed by making an opening in 

 the transverse meso-colon. 



In some cases the first few centimetres of the jejvmum are found to be fused between the 

 layers of the transverse meso-colon. Certain peritoneal fosste are often found on the left side 

 of the flexure. They may give rise to retro-peritoneal hernia and strangulation of intestine. 

 The duodenal fossae are described on p. 1164. 



Jejunum and ileum. — The mesentery contains between its two peritoneal 

 layers the superior mesenteric vessels and their intestinal branches, the superior 

 mesenteric plexus, lacteals and many lymph nodes on their course. These 

 nodes are frequently enlarged in abdominal tuberculosis in children (tabes 

 mesenterica). The attached border of the mesentery may be marked out 

 on the surface by a line drawn from just below the transpyloric plane and a little 

 to the left of the middle line (the duodeno-jejunal flexure), which curves downward 

 and to the right to end in the iliac fossa at the junction of the intertubercular 

 and right lateral vertical lines (the ileo-caecal valve). 



Meckel's diverticulum which is present in about 2 per cent, of subjects (Treves) is found in 

 the free border of the ileum 30 cm. to 1 m. (1 to 3 ft.) above the ileo-csecal valve. It is a remains 

 of the vitello-intestinal duct. It is usually a blind conical pouch some 6 to 9 cm. long with a 

 free extremity, but may be attached to the umbilicus by a fibrous cord. This cord may cause 

 acute intestinal obstruction by strangulating a coil of gut, or the diverticulum may be invag- 

 inated and form the starting-point of an intussusception. 



The presence of aggregated lymph nodules (Peyer's patches) in the lower part of the ileum 

 accounts for the fact that tuberculous ulcers and perforating typhoid ulcers are almost confined 

 to this part of the gut. 



Intestinal localisation. — It often happens that the surgeon wishes to ascertain 

 roughl}' to what part of the small intestine a given coil presenting in a wound 

 belongs. The variations in length of the small intestine and the considerablf- 

 range of movement of the coils during peristalsis render the problem difficult, 

 but it may be stated as a general rule that the upper third of the intestine lies 

 in the left hypochondrium and is not usually encountered in a wound; the 

 middle third occupies the middle part of the abdomen, and the lower third lies 

 in the pelvis and right iliac fossa (Monks). The jejunum is thicker walled and 

 more vascular than the ileum. The lumen steadily diminishes as we pass 

 downward, hence foreign bodies such as gall-stones that pass through the jeju- 

 num are apt to become impacted in the lower ileum. 



The most reliable indications of the level of a given coil are found, however, on inspection 

 of the mesentery and its blood-vessels (see fig. 482 in Section V). Opposite the upper part of 

 the bowel the mesenteric arteries are arranged in a series of large primary anastomosing loops. 

 I'>om these the vasa recta run to the gut 3 to 5 cm. long, straight and unbranched. Passing 

 downward toward the lower end, the single large primary loops give place to smaller and more 

 numerous secondary loops arranged in layers coming nearer and nearer to the bowel. Hence 

 the va.sa recta become shorter. They become also less regular and more branched, and in the 

 lower third of the small intestine arc Ics.s than 1 cm. in length. The mesenteric fat in the upper 

 third never reaches c|uite to the free edge of the mensentery, so that clear transparent spaces 

 arc left near the bowel. In the lower third the fat usually occupies the whole of the mesentery 

 right up to the intestine, and makes it thicker and more opaque.* 



The average width of the mesentery, from its root at the posterior parietes to the bowel 

 is 20 cm. (8 in.) and the longest part lies between 2 and 8 in. from the duodenum (Treves). 

 The ileum is fretily movable on a long mesentery down to the ileo-cajcal region. In some cases 

 hf)wever a (•()ngenital fusion of the; hjft half of the mes(!ntery with the parietal peritoneum near 

 the pelvic brim binds the bowel down a few inches above the ileo-ca^cal valve, and has been said to 

 give rise to symptoms of intestinal stasis. (I''!int,t Gray, and Anderson.) 



(B) Large intestine. Ileo-caecal region. — The position of the ileo-ca^cal 

 valve may l)c marked on the surface by the junction of the intertubercular and 

 right lateral vertical lines, though it is often found consideral)ly lower. It is 

 situated on the postero-medial aspect of the caicum. The caecum, which is the 



* Monks: Trans. Airier. Surg. Assoc, 1913. 



t Bulletin, Johns Hopkins Hospital, Oct., 1912. 



