Chapter 68: Pancreas Anatomy

The pancreas functions both as one of the body’s largest digestive glands, performing a primary exocrine role by secreting essential enzymes necessary for the breakdown of proteins, lipids, and carbohydrates, and an important endocrine role derived from specialized cell clusters that regulate glucose homeostasis. This retroperitoneal organ typically measures between 12 and 15 cm in length and is structurally divided into four regions: the head, which includes the hook-shaped uncinate process; the neck; the body; and the tail. The consistency of the pancreas is surgically relevant, as a harder gland is associated with a lower risk of fluid leakage after reconstruction procedures. The highly complex arterial supply originates from the coeliac trunk and the superior mesenteric artery, forming interconnected vascular networks known as the anterior and posterior pancreaticoduodenal arcades that supply the head and uncinate process, while the body and tail are largely nourished by multiple branches of the splenic artery. Venous drainage occurs primarily into the hepatic portal, superior mesenteric, and splenic veins. Exocrine products drain via the main pancreatic duct (of Wirsung), which usually joins the bile duct to form the hepatopancreatic ampulla before entering the duodenum at the major papilla. A significant anatomical variant, pancreas divisum, occurs when the dorsal and ventral ducts fail to fuse, forcing most pancreatic drainage through the narrow minor duodenal papilla via the accessory pancreatic duct (of Santorini), increasing the risk of recurrent pancreatitis. Histologically, the gland is primarily exocrine acinar tissue, with the islets of Langerhans embedded throughout, containing essential cell types such as beta cells (insulin) and alpha cells (glucagon) that release hormones directly into the richly fenestrated capillary network. The extensive innervation, especially dense in the head and neck regions, contributes to the characteristic referred pain often experienced in the lower back in cases of chronic inflammation or pancreatic cancer, which sometimes necessitates ablation of the coeliac plexus for control. Pathologies, including tumors of the head, often necessitate complex resections like the pancreaticoduodenectomy (Whipple procedure), where major vessel involvement, particularly the superior mesenteric or hepatic portal veins, critically determines the tumor's resectability.