THE DUODENUM. 



369 



BPECIAIi CHARACTERS AND CONNECTIONS OF THE SEVERAL PARTS 

 OP THE SMALL INTESTINE. 



DuoDENOTi. — This is the shortest aud widest part of the small intes- 

 iine. In length ib measures 10 or 12 inches, or about the breadth of 

 twelve fingers ; hence its name. 



It varies in diameter between an inch and a half and two inches. 

 In its course it describes a single large curve somewhat resembling a 

 horseshoe, the convexity of which is turned towards the right, whilst 

 the concavity embraces the head of the pancreas. 



Fict. 266. 



Fig. 266. —View of thk Duodenum from 

 BEFOKE (.slightly altered from LiLsclika). ^ 



12, tlie twelfth dorsal vertebra and rib ; 1, 

 3, 4, 5, transverse i)rocesses of the tinst, third, 

 fourth, and fifth left lumbar vertebrte ; 2, 

 that of the second on the right side ; «, «, the 

 abdominal aorta above the cadiac axis and also 

 near the bifurcation ; m, superior mesenteric 

 arteiy ; v, v, the vena cava above the renal 

 veins and near the bifurcation ; p, placed on 

 the first part of the duodenum, points to the 

 pyloric orifice seen from the side next the 

 stomach, of which a small part is left con- 

 nected with the intestine ; d, on the descend- 

 ing or second part of the duodenum, indicates 

 the termination of the common bile-duct and 

 the pancreatic duct ; d', the tlurd or oblique 

 part of the d uodenum ; j, the commencement 

 of the jejunum. 



It has no mesentery, and is covered only partially by the peritoneum. 

 Its muscular coat is comparatively thick, and its mucous membrane 

 towards the pylorus is the seat of the glands of Brunner, already 

 described. The common bile-duct and the pancreatic duct open into 

 this part of the intestinal canal. 



Three portions of the duodenum are described by anatomists. 



The first, or siqmior portion, between two and three inches long, 

 extends from the pylorus upwards, backwards, and to the right, as far 

 as beneatli the neck of the gall-bladder, where it bends suddenly down- 

 wards. The first portion of the duodenum is for the most part free, 

 and invested by peritoneum like the stomach. Above, and in front of 

 it, are the liver and gall-bladder, and it is commonly found stained by 

 the exudation of bile from the latter a few hours after death. Behind 

 it is tlie biliary duct, with the blood-vessels passing up to the liver. 



The second, or descendhhj portion, commencing at tlie bend below the 

 neck of the gall-bladder passes downwards as low as the second or third 

 lumbar vertebra, where the bowel turns across to the left to form the 

 third portion. This part of the duodenum is invested by the perito- 

 neum on its anterior surface only, — the posterior surface being con- 

 nected to the right kidney and the vertebral column by areolar tissue. 

 In front is the transverse colon and mesocolon, the upper layer of 

 which is continuous with the peritoneal covering of the duodenum. To 

 the left is the head of the pancreas (see fig. 2b2), whicli adapts itself to 



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