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The pancreas (plural: pancreata) is an unpaired, mostly retroperitoneal organ that has endocrine and exocrine functions, with a role in glucose metabolism and digestion.
The pancreas is located at approximately the L1-L2 vertebral level in the anterior pararenal space of the retroperitoneum with the exception of its tail, which is intraperitoneal. It is an elongated, mostly midline structure that extends further left laterally. It lies slightly oblique with its tail more superior to its head. Developmentally, it is considered a secondary retroperitoneal structure 6.
The diameter of the pancreatic head does not exceed the transverse diameter of the adjacent vertebral body 9.
The pancreas may have the shape of a dumbbell, tadpole, or sausage. It can be divided into four main parts:
uncinate process: extension of the head, posterior to SMV, SMA 1
lies within "C" shaped concavity of duodenum (D2 and D3)
neck: thinnest part; lies anterior to SMA, SMV
SMV joins splenic vein behind pancreatic neck to form portal vein
body: main part; lies to left of SMA, SMV
anterior surface is covered with peritoneum forming the posterior surface of the omental bursa (lesser sac)
splenic vein lies in groove on posterior surface of body
tail: lies between layers of the splenorenal ligament in the splenic hilum and is the only intraperitoneal part
Pancreatic juice is secreted into a branching system of pancreatic ducts that extend throughout the gland. In the majority of individuals, the main pancreatic duct empties into the second part of duodenum at the ampulla of Vater.
See article: pancreatic ducts for more information.
The pancreas is involved in production of endocrine hormones, including insulin, glucagon, and somatostatin. Its exocrine function is secretion of enzymes involved in the break down of carbohydrates, proteins and lipids.
L1/L2 vertebral body
common bile duct grooves posterior surface of upper part of head close to duodenum
aorta behind neck and uncinate process
left kidney hilum, left suprarenal gland
splenic vein joined by inferior mesenteric vein, and confluence of splenic vein and superior mesenteric vein to form portal vein
lesser sac separating it from stomach
lesser omentum and liver through it above the lesser curvature
attachment of transverse mesocolon across head and lower margin of neck and body
D1 duodenum anterior to (or above) head of pancreas
infracolic compartment in front of lower part of head, neck and body
origin of celiac trunk
common hepatic artery runs to the right across upper margin of head and neck
splenic artery runs to the left across upper margin of body
Arterial supply to the head is primarily from the inferior and superior pancreaticoduodenal arteries. Branches of the splenic artery supply the neck, body and tail via multiple branches including the dorsal pancreatic artery, greater pancreatic artery (arteria pancreatica magna) and transverse pancreatic artery.
Venous return is by numerous small veins into the splenic hilum. From the head the superior pancreaticoduodenal vein drains into the portal vein and the inferior pancreaticoduodenal vein drains into the superior mesenteric vein.
follows blood vessels → collects in splenic, celiac, superior mesenteric and hepatic nodes
accessory pancreas when head beneath mesenteric vessels separate
pancreatic duct variations
pancreatic clefts: linear clefts may be seen which contain fat where small vessels enter the pancreas and are a common mimic of pancreatic laceration. They are most prominent at the junction of the body and neck 2
portal annular pancreas
agenesis or hypoplasia of the pancreas (rare)
In contrast enhanced abdominal CT, fat planes between the pancreatic parenchyma and major arteries (celiac trunk, common hepatic artery and superior mesenteric artery) and inferior vena cava are always visible. Fat planes are variably present between the pancreas with splenic vein, superior mesenteric vein and stomach. In contrast, the fat plane between the pancreas and portal vein and medial duodenal wall are always invisible 7.
The primitive pancreas develops from separate primordial buds in the dorsal and ventral mesogastrium, representing small evaginations from the foregut. The buds form around 32 days after ovulation and migrate to fuse into one gland at 41 days.
dorsal pancreatic bud
develops into the anterior part of the head, body, and tail (and a small variable portion of the uncinate process)
contains a long duct continuing from the accessory pancreatic papilla to the tail
ventral pancreatic bud
smaller of the two buds that develops into the posterior part of the pancreatic head and most of the uncinate process
contains a short main pancreatic duct which is connected to the common bile duct
develops just distal to the developing biliary tree
starts to the right of the duodenum
rotates to the left underneath the dorsal pancreas
The ducts continue to fuse throughout the second and third trimesters but often continue into the neonatal period. Most of the dorsal duct drains into the proximal part of the ventral duct. The remaining proximal part of the dorsal duct forms the accessory duct.
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