Pancreas is a gland that produces digestive secretions and hormones that regulate blood glucose, the sugar carried in the blood. It lies across the upper abdomen, mainly behind the stomach, extending from the duodenum, the first part of the small intestine, towards the spleen on the left.
Where is the pancreas located?
Most of the pancreas is retroperitoneal: it lies behind the peritoneum, the membrane lining the abdominal cavity and covering many abdominal organs. The tail is the exception, extending between the layers of a peritoneal fold called the splenorenal ligament towards the spleen.
The stomach lies in front of the pancreas, separated from it by the lesser sac, a space within the peritoneal cavity. Behind the pancreas are major blood vessels, including the aorta, the main artery supplying the body, and the inferior vena cava, the large vein returning blood from the lower body. The left kidney also lies behind the gland.
The duodenum curves around the pancreatic head. The transverse colon, the crosswise part of the large intestine, lies below and in front of the gland. Its supporting fold, the transverse mesocolon, crosses the anterior surface of the pancreatic head and attaches along the anterior border of the body.
What are the parts of the pancreas?
The regions of the pancreas are named by their position and shape. Following them from right to left gives a useful framework for understanding neighbouring vessels and organs.
| Part | Position and main relation |
|---|---|
| Head of pancreas | Broad right-hand region within the curve of the duodenum. |
| Uncinate process of pancreas | Projection from the lower head that extends behind the superior mesenteric vessels, which supply and drain much of the intestine. |
| Neck of pancreas | Short region between the head and body, lying in front of the formation of the portal vein. |
| Body of pancreas | Central region crossing towards the left, behind the stomach. |
| Tail of pancreas | Narrow left end approaching the hilum of the spleen, where its vessels enter and leave. |
The portal vein, which carries blood from digestive organs towards the liver, forms behind the neck where the splenic and superior mesenteric veins join. The common bile duct, which carries bile towards the duodenum, passes in a groove on the posterior surface of the head or through its substance.
The body has anterior, posterior and inferior surfaces, facing forwards, backwards and downwards respectively. These surfaces help organise its relations to the stomach, posterior abdominal structures and intestinal loops.
How are pancreatic tissue and ducts organised?
The parenchyma of pancreas is its functional tissue. It contains acini, clusters of secretory cells arranged around small central spaces, and pancreatic islets, groups of hormone-producing cells scattered among them. Connective tissue divides the gland into small compartments called lobules and supports its vessels and ducts.
The pancreatic duct tree is the branching network that collects secretions from the acini. Small ducts join larger channels, which drain towards the main pancreatic duct. This duct runs from the tail through the body towards the head.
The main duct usually joins the common bile duct before opening into the duodenum at the major duodenal papilla, a small elevation on its inner wall. An accessory pancreatic duct may drain part of the head through a separate opening called the minor duodenal papilla. The connections between these ducts vary.
What does the pancreas do?
The pancreas has exocrine and endocrine functions. Exocrine secretion passes through ducts onto a surface; here, digestive fluid enters the gastrointestinal tract, the continuous passage through which food travels. Endocrine secretion releases hormones into the blood.
- The acinar cells produce digestive enzymes, proteins that help break down food. Some are released as inactive precursors that become active in the intestine.
- Duct cells add fluid rich in bicarbonate, which helps neutralise acidic contents arriving from the stomach.
- The pancreatic islets release hormones, including insulin and glucagon, which help regulate blood glucose.
These functions occupy different tissue components within the same gland. Digestive secretions leave through the ducts, whereas hormones enter nearby blood vessels.
What is the blood supply of the pancreas?
The head receives blood through connected arterial routes around the pancreas and duodenum. Superior pancreaticoduodenal arteries arise from the gastroduodenal artery, while the inferior pancreaticoduodenal artery usually arises from the superior mesenteric artery, either independently or through a common trunk with a jejunal artery. Their connections form arterial arcades, loops that allow blood to reach the region from both directions.
The body and tail receive pancreatic branches of the splenic artery, which runs along the upper border of the gland. Pancreaticoduodenal veins drain the head, while veins from the body and tail drain mainly into the splenic vein. These routes ultimately carry pancreatic venous blood into the portal vein.
Which nerves supply the pancreas?
The pancreatic plexus, a network of nerves around the gland and its vessels, carries autonomic fibres. These are nerves involved in involuntary control of glandular activity and blood vessels.
Parasympathetic fibres, associated with digestive activity, arrive through the vagus nerve (X). Sympathetic fibres reach the pancreas through upper abdominal nerve networks, including connections from the celiac ganglia, clusters of nerve cell bodies. Sensory fibres also travel through these networks.
Where does pancreatic lymph drain?
Lymph is fluid collected from tissue spaces and carried through lymphatic vessels. Pancreatic lymphatic vessels generally follow the blood vessels towards regional lymph nodes, small structures that filter lymph.
Drainage reaches splenic lymph nodes along the splenic vessels, as well as superior mesenteric lymph nodes and celiac lymph nodes. The routes reflect the close anatomical relationships between the pancreas, spleen, duodenum and major abdominal arteries.
How can I locate the pancreas in the 3D model?
In the 3D model beside this article, rotate and zoom to examine the upper abdomen, then select and isolate the pancreas. Hide or fade surrounding structures, switch layers, or cut a section along the sagittal, coronal or transverse plane to explore spatial relationships.