The pancreas is considered the largest of the digestive glands. It is located mostly posterior to the stomach, and extends across the posterior abdominal wall, from the right, to the hilum of the spleen, on the left. The pancreas lies within the first, second, and third parts of the duodenum, and performs a range of both endocrine and exocrine functions. It is involved in glucose homeostasis, and upper gastrointestinal motility and function. Moreover, it secretes various enzymes that are involved in lipid, carbohydrate, and protein digestion.
The pancreas is a salmon pink flattened structure, with a smooth lobulated surface that is thicker at its medial end and thinner at its lateral end. It lies mostly in the retroperitoneal cavity, except for a small portion of its tail. Typically, the pancreas is divided into five parts: the head, the uncinate process, the neck, the body, and the tail.
The head is the widest part of the pancreas. It lies within the C-shaped concavity created by the duodenum, and is connected to this structure by connective tissue.
The uncinate process is a hook-like projection from the inferior part of the pancreatic head, which extends medially below the body of the pancreas. It passes posterior to the superior mesenteric vessels.
The neck of the pancreas is short, and is located between the pancreatic head and body. It is situated anterior to the superior mesenteric vessels, which mark its posterior aspect.
The body of the pancreas extends from the pancreatic neck to the tail. It is positioned centrally, crossing the midline of the human body to lie to the left of the superior mesenteric vessels.
The tail passes anterior to the left kidney, where it is closely related to the splenic hilum and the left colic flexure. It is contained within the layers of the splenorenal ligament along with the splenic vessels.
The pancreatic duct begins at the tail, and is formed by the junction of several secondary lobular ducts. As it reaches the neck of the pancreas, it turns inferiorly and posteriorly to join the bile duct. These two ducts form hepatopancreatic ampulla, which enters into the second descending part of the duodenum at the major duodenal papilla. A smaller accessory pancreatic duct also functions to empty into the duodenum, just above the major duodenal papilla, at the minor duodenal papilla. It usually communicates with the pancreatic duct via several small branches.
The arterial supply of the pancreas is rich and derived from the celiac trunk and the superior mesenteric artery. It is supplied by pancreatic branches originating from the splenic artery, and the superior and inferior pancreaticoduodenal arteries originating from the gastroduodenal and superior mesenteric arteries, respectively. The venous drainage of the pancreas flows via corresponding pancreatic veins and tributaries, from the splenic and superior mesenteric parts of the hepatic portal vein. Most of these veins drain into the splenic vein. The pancreas is innervated by nerves derived from the vagus (CN X) and abdominopelvic splanchnic nerves passing through the diaphragm. The networks of parasympathetic and sympathetic fibers reach the pancreas by passing along the celiac and superior mesenteric plexus.