The Pancreas

Anatomical Position & Relations

The pancreas is an oblong-shaped organ located at the level of the transpyloric plane (L1). With the exception of its tail, it is a retroperitoneal structure, lying deep within the epigastric and left hypochondriac regions of the upper abdomen.

Organs

The pancreas has close anatomical relationships with several surrounding abdominal organs:

• Stomach – lies anterior to the pancreas, separated from it by the lesser sac.
• Duodenum – curves around the head of the pancreas. The first part passes anterior to the head, while the second part lies lateral to its right.
• Common bile duct – Passes posterior to the head of the pancreas, then joins the main pancreatic duct. Together, they open into the second part of the duodenum.
• Spleen – Positioned posterolateral to the pancreas. It is connected to the tail of the pancreas by the splenorenal ligament, a fold of peritoneum that also contains the splenic vessels.
• Transverse mesocolon – A fold of peritoneum that attaches the transverse colon to the posterior abdominal wall. It is anchored to the anterior surface of the pancreas.

Vascular Structures

The pancreas lies in close proximity to several major vessels:

• Aorta and inferior vena cava – pass posterior to the head of the pancreas.
• Superior mesenteric artery – runs behind the neck of the pancreas and anterior to the uncinate process.
• Portal vein – formed posterior to the neck of the pancreas by the union of the splenic and superior mesenteric veins.
• Splenic artery – courses along the superior border of the pancreas as it travels from the coeliac trunk to the hilum of the spleen.

By TeachMeSeries Ltd (2025)

Fig 1
Anterior view of the abdomen. The stomach, transverse colon, and the majority of the small intestine have been removed to expose the underlying pancreas

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Anatomical Structure

The pancreas is typically divided into five parts:

• Head – the widest part, which lies within the C-shaped curve of the duodenum and is connected to it by connective tissue.
• Uncinate process – a hook-like projection from the lower part of the head, extending medially to lie beneath the body of the pancreas. It lies posterior to the superior mesenteric vessels.
• Neck – located between the head and body, it overlies the superior mesenteric vessels, which create a groove on its posterior aspect.
• Body – the central portion, crossing the midline and lying posterior to the stomach and to the left of the superior mesenteric vessels.
• Tail – the left-most part, which lies in close proximity to the splenic hilum. It is the only intraperitoneal part of the pancreas, contained within the splenorenal ligament along with the splenic vessels.

By TeachMeSeries Ltd (2025)

Fig 2
The parts of the pancreas

Duct System

The exocrine pancreas is classified as a lobulated, serous gland which produces digestive enzyme precursors. It is composed of approximately one million ‘berry-like’ clusters of cells called acini, connected by short intercalated ducts.

The intercalated ducts unite with those draining adjacent lobules and drain into a network of intralobular collecting ducts, which in turn drain into the main pancreatic duct.

The pancreatic duct runs the length of the pancreas and unites with the common bile duct, forming the hepatopancreatic ampulla of Vater. This structure then opens into the duodenum via the major duodenal papilla.

Secretions into the duodenum are controlled by a muscular valve – the sphincter of Oddi. It surrounds the ampulla of Vater, acting as a valve.

By TeachMeSeries Ltd (2025)

Fig 3
The exocrine pancreas, secreting into the duodenum

Vasculature

The pancreas is supplied by the pancreatic branches of the splenic artery. The head is additionally supplied by the superior and inferior pancreaticoduodenal arteries which are branches of the gastroduodenal (from coeliac trunk) and superior mesenteric arteries, respectively.

Venous drainage of the head of the pancreas is into the superior mesenteric branches of the hepatic portal vein. The pancreatic veins draining the rest of the pancreas do so via the splenic vein.

By TeachMeSeries Ltd (2025)

Fig 4
The arterial supply and venous drainage of the pancreas

Lymphatics

The pancreas is drained by lymphatic vessels that follow the arterial supply. They empty into the pancreaticosplenal nodes and the pyloric nodes, which in turn drain into the superior mesenteric and coeliac lymph nodes.