Which of the following statement(s) is/are true concerning the anatomy of the small intestine?

a. The second (descending), third (transverse) and fourth (ascending) portions of the duodenum lie in the retroperitoneum and are mobilized for surgical procedures via the Kocher maneuver

b. The identification of the superior mesenteric vein and artery can be facilitated by an extensive Kocher maneuver mobilizing the transverse portion of the duodenum and exposing the vessels as they course over the duodenum and under the neck of the pancreas

 The duodenum is divided into four parts-the bulb, followed by the second (descending), third (transverse), and fourth (ascending) portion. The duodenal bulb begins at the pylorus and extends for the next 5 cm as the duodenum assumes a retroperitoneal position for the second, third, and fourth portion. The third and fourth portion of the duodenum complete the duodenal sweep. Mobilization of the duodenum from the retroperitoneum for a multitude of abdominal procedures can be facilitated by the Kocher maneuver where the retroperitoneal attachment is divided and the duodenum and head of the pancreas can be brought out of its retroperitoneal position. Endoscopically, the major papilla of the duodenum can be seen entering at the mid-point of the second portion of the duodenum. The papilla (ampulla of Vater) appears anatomically as a hooded fold, marking the confluence of the common bile duct and the main pancreatic duct (duct of Wirsung) and is surrounded by the muscular sphincter of Oddi. In some 50% to 60% of patients, an accessory pancreatic duct (the duct of Santorini) can be seen entering the duodenum proximal to the ampulla of Vater. Endoscopically, this lesser, or minor, papilla appears as a one-to-three mm sessile polyp. The jejunum is the portion of the small bowel that courses from the ligament of Treitz to an arbitrary point approximately two-fifths of the distance to the ileocecal valve. The length of the jejunum has been estimated at 100 cm although this distance can vary dramatically depending on the status of the small intestine. The jejunum is the widest portion of the small intestine, and the diameter progressively decreases as the ileocecal valve is approached. The ileum makes up the distal three-fifths of the combined jejunal/ileal length.