The pancreas arises in the fourth week of fetal life from the
caudal part of the foregut as dorsal and ventral pancreatic buds.
Both anlagen rotate to the right and fuse near the point of origin
of the ventral pancreas. Later, as the duodenum rotates, the pancreas
shifts to the left. In the adult, only the caudal portion of the head
and the uncinate process are derived from the ventral pancreas.
The cranial part of the head and all of the body and tail are derived
from the dorsal pancreas. Most of the dorsal pancreatic duct joins
with the duct of the ventral pancreas to form the main pancreatic
duct (duct of Wirsung); a small part persists as the
accessory duct (duct of Santorini). In 5–10% of
people, the ventral and dorsal pancreatic ducts do not fuse, and most
regions of the pancreas drain through the duct of Santorini and
the orifice of the minor papilla. In this case, only the small ventral
pancreas drains with the common bile duct through the papilla of
The pancreas is a thin elliptic organ that lies within the retroperitoneum
in the upper abdomen (Figures 26–1 and 26–2). In the adult, it is 12–15
cm long and weighs 70–100 g. The gland can be divided into
three portions: head, body, and tail. The head of the pancreas is
intimately adherent to the medial portion of the duodenum and lies
in front of the inferior vena cava and superior mesenteric vessels.
A small tongue of tissue called the uncinate process lies behind the
superior mesenteric vessels as they emerge from the retroperitoneum.
Anteriorly, the stomach and the first portion of the duodenum lie
partly in front of the pancreas. The common bile duct passes through
a posterior groove in the head of the pancreas adjacent to the duodenum. The
body of the pancreas is in contact posteriorly with the aorta, the
left crus of the diaphragm, the left adrenal gland, and the left
kidney. The tail of the pancreas lies in the hilum of the spleen.
The main pancreatic duct (the duct of Wirsung) courses along the
gland from the tail to the head and joins the common bile duct just
before entering the duodenum at the ampulla of Vater. The accessory
pancreatic duct (the duct of Santorini) enters the duodenum 2–2.5 cm
proximal to the ampulla of Vater (Figure 26–1).
Anatomic configuration of pancreatic ductal system.
(Courtesy of W Silen.)
Arterial supply and venous drainage of the pancreas.
(Courtesy of W Silen.)
The blood supply of the pancreas is derived from branches of
the celiac and superior mesenteric arteries (Figure
26–2). The superior pancreaticoduodenal artery arises
from the gastroduodenal artery, ...