Pancreas

At a glance

English

Pancreas

Latin (TA2)

Pancreas

System

Digestive

Region

Abdomen

Side

Single, on the midline

About the pancreas

The pancreas stretches almost horizontally across the posterior abdominal wall, behind the stomach and the lesser sac, at about the level of the first and second lumbar vertebrae. It is roughly 15 cm long, and anatomists name four regions along it: head, neck, body, tail. The broad head lies to the right in the curve of the duodenum, with a hooked uncinate process tucked behind the superior mesenteric vessels. The narrow neck passes in front of those vessels and the start of the portal vein, the body crosses the aorta and left kidney, and the tail ends at the hilum of the spleen. Apart from the tail, which lies in the splenorenal ligament, it is retroperitoneal.

Its relations explain much of its clinical behaviour. The bile duct runs through or behind the head, the splenic vein lies in a groove on the back of the body, and the splenic artery winds along its upper border. The transverse mesocolon is attached along its front, dividing it into an upper surface facing the lesser sac and a lower surface facing the small bowel.

It is two glands in one. Most of the tissue is exocrine: clusters of acinar cells make an alkaline juice full of enzymes for proteins, fats and starches, which drains through the main and accessory pancreatic ducts into the duodenum. Scattered through it are the islets of Langerhans, the endocrine part, whose cells release insulin and glucagon into the blood to control blood sugar, with somatostatin and pancreatic polypeptide.

Acute pancreatitis, most often triggered by a gallstone at the ampulla or by alcohol, gives severe upper abdominal pain spreading to the back. Repeated inflammation can scar the gland, causing poor digestion and diabetes. Cancers of the head often show as painless jaundice when they press on the bile duct, while those of the body and tail tend to be found late. Loss of the insulin-making cells causes type 1 diabetes.

Function and supply

Function

Secretes digestive enzymes and bicarbonate into the duodenum, and releases insulin, glucagon and other hormones into the blood to regulate glucose.

Nerve supply

Vagal parasympathetic fibres stimulate secretion; sympathetic fibres from the coeliac and superior mesenteric plexuses carry pain, which is felt in the epigastrium and back.

Blood supply

The head from the pancreaticoduodenal arcades, superior and inferior (from the gastroduodenal and superior mesenteric arteries); the neck, body and tail from pancreatic branches of the splenic artery. Veins drain to the portal system.