The pancreas is an abdominal glandular organ, with a digestive (exocrine) and hormonal (endocrine) function.
In this article, we shall look at the anatomy of the pancreas – its structure, anatomical position and neurovascular supply.
The pancreas is an oblong-shaped and flattened organ, about the size of a hand. Aside from the tail, it is a retroperitoneal structure (lies behind the peritoneal cavity), located deep within the upper abdomen in the epigastrium and left hypochodrium regions.
Within the abdomen, the pancreas is surrounded by other viscera and vessels:
- Stomach – lies anteriorly and superiorly.
- Duodenum – situated anteriorly and medially, curving around the head of the pancreas.
- Spleen – located posteriorly and laterally. It is connected by ligaments to the tail of the pancreas.
- Vasculature – the aorta and inferior vena cava pass posteriorly to the head of the pancreas.
The pancreas is typically divided into five parts;
- Head: This is the widest part of the pancreas. It lies within the C-shaped curve created by the duodenum, and is connected to it by connective tissue.
- Uncinate process: This is a projection arising from the lower part of the head and extending medially to lie beneath the body of the pancreas. It lies posterior to the superior mesenteric vessels.
- Neck: Located between the head and the body of the pancreas. It overlies the superior mesenteric vessels which form a groove in its posterior aspect.
- Body: The body is centrally located, crossing the midline of the human body to lie behind the stomach and to the left of the superior mesenteric vessels.
- Tail: The left end of the pancreas that lies within close proximity to the hilum of the spleen. It is contained within the splenorenal ligament with the splenic vessels. This is the only part of the pancreas that is intraperitoneal.
The Duct System
The exocrine compartment is classified as a serous gland. It is composed of approximately a million ‘berry-like’ clusters of cells called acini, connected by short intercalated ducts.
Intercalated duct cells beginning within acini are called centroacinar cells. The intercalated ducts 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 opens into the duodenum.
Secretions into the duodenum are controlled by a muscular valve – the sphincter of Oddi. It surrounds the ampulla of Vater, acting as a valve.
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 into the splenic vein.
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.
Clinical Relevance: Pancreatitis
The pancreas can become inflamed and cause pancreatitis – this is can be acutely or persist over a long period of time and cause chronic pancreatitis. To remember the causes of acute pancreatitis there is a little mnemonic – I GET SMASHED:
- Gall stones
- Scorpion stings
- Hypertriglyceridaemia and hypercalcaemia
- ERCP – endoscopic retrograde cholangiopancreatography
- Drugs – such as sodium valproate, azathioprine and metformin
Pancreatitis creates severe epigastric pain which can radiate to the back and also cause nausea, vomiting and diarrhoea.
Treatment involves supportive measures such as IV fluids, painkillers and oxygen. The underlying cause will then also need to be treated.