THK DUODENUM 1283 



(6 m.) in length/ and gradually diminishes in size from its commencement 

 to its termination. It is contained in the central and lower part of the abdominal 

 cavity, and is surrounded above and at the sides by the large intestine; a portion 

 of it extends below the brim of the pelvis and lies in front of the rectum. 

 It is in relation, in front, with the great omentum and abdominal parietes, and 

 the greater part of it is connected to the vertebral column by a fold of peritoneum, 

 the mesentery (p. 1263). The small intestine is divisible into three portions 

 the duodenum, the jejunum, and the ileum. 



The Duodenum (Figs. 1007, 1014). 



The duodenum has received its name from being about equal in length to the 

 breadth of twelve fingers (ten inches). It is the shortest, the widest, and the most 

 fixed part of the small intestine, and has no mesentery, being only partially covered 

 by peritoneum. Somewhat more than the upper half of the duodenum is placed 

 in the epigastric region; the remainder is in the umbilical region. Its course 

 presents a remarkable curve, somewhat of the shape of an incomplete circle, 

 so that its termination is not far removed from its beginning. 



In the adult the course of the duodenum is as follows: Commencing at the 

 pylorus it passes backward, upward, and to the right, beneath the quadrate lobe 

 of the liver to the neck of the gall-bladder, varying slightly in direction according 

 to the degree of distention of the stomach ; it then takes a sharp curve and descends 

 along the right margin of the head of the pancreas, for a variable distance, gener- 

 ally to the level of the upper border of the body of the fourth lumbar vertebra. 

 It now takes a second bend, and passes from right to left across the front of the 

 vertebral column, having a slight inclination upward; and to the left side of the 

 vertebral column it ascends for about an inch, and then terminates opposite the 

 second lumbar vertebra in the jejunum. As it unites with the jejunum it turns 

 abruptly forward, forming the duodenojejunal flexure. From the above descrip- 

 tion it will be seen that the duodenum may be divided into four portions superior, 

 descending, transverse, and ascending. 



The first or superior portion (pars superior) (Figs. 1007 and 1008) is about two 

 inches (5 cm.) in length. Beginning at the pylorus, it ends at the level of the neck 

 of the gall-bladder. It is the most movable of the four portions. It is almost 

 completely covered by peritoneum derived from the two layers of the lesser omen- 

 tum, but a small part of its posterior surface near the neck of the gall-bladder 

 and the inferior vena cava is mncovered (Fig. 1008). It is in such close relation 

 with the gall-bladder that it is usually found to be stained by bile after death, 

 especially on its anterior surface. It is in relation above and in front with the 

 quadrate lobe of the liver, lying in a slight concavity, the impressio duodenalis, and 

 the gall-bladder; behind, with the gastroduodenal artery, the common bile duct, 

 and the portal vein; and below, with the head of the pancreas. 



The second or descending portion (pars descendens) (Figs. 1007 and 1009) is 

 between three and four inches (7.5 to 10 cm.) in length, and extends from the neck 

 of the gall-bladder on a level with the first lumbar vertebra along the right side 

 of the vertebral column as low as the body of the fourth lumbar vertebra. It is 

 crossed in its middle third by the transverse colon, the posterior surface of which 

 is uncovered by peritoneum and is connected to the duodenum by a small quantity 

 of connective tissue. The portions of the descending part of the duodenum above 

 and below this interspace are named the supracolic and infracolic portions, and are 



1 Treves states that in one hundred cases the average length of the small intestine in the adult male was 22 

 feet 6 inches, and in the adult female 23 feet 4 inches; but that it varies very much, the extremes in the male 

 being 31 feet 10 inches in one case and 15 feet 6 inches in another, a difference of over 15 feet. He states that 

 he has convinced himself that the length of the bowel is independent, in the adult, of age, height, and weight. 



