Pancreas

Anatomy

Function

The pancreas is a unique organ because it fulfills both exocrine and endocrine roles. Its exocrine function includes the synthesis and release of digestive enzymes into the duodenum of the small intestine. Its endocrine function involves the release of insulin and glucagon into the bloodstream, two important hormones responsible for regulating glucose, lipid, and protein metabolism. 

The main players responsible for pancreatic function are endocrine and exocrine glands. The latter synthesize inactive pancreatic digestive enzymes (zymogens), which are released into the glandular and pancreatic ductal systems. Upon reaching the duodenum, the zymogens are activated by proteolytic enzymes, becoming active peptidases, amylases, lipases and nucleases which act to further digest food entering the small intestine from the stomach.

The endocrine function of the pancreas is carried out by the pancreatic islets of Langerhans. These endocrine glands secrete hormones directly into the bloodstream and consist of three main cell types (alpha, beta, and delta) which. Don’t worry, you don’t need to know the entire Greek alphabet to understand the functions of the pancreas! In a nutshell, beta cells secrete insulin, alpha cells release glucagon, and delta cells produce somatostatin. These hormones are crucial in regulating glucose metabolism and gastrointestinal functions.

If you want a more in-depth explanation about the internal structure, including the histology of the pancreas, take a sneak peek below. Its functions and the endocrine system are also explained.

Blood vessels

The pancreas receives its blood supply from several sources. The uncinate process and head are supplied by the superior and inferior pancreaticoduodenal arteries, which are branches of the gastroduodenal and superior mesenteric arteries respectively. Each pancreaticoduodenal artery has anterior and posterior branches that project along the respective faces of the pancreatic neck where they form pancreaticoduodenal arcades and supply them with arterial blood.

In turn, the body and tail of the pancreas are supplied by pancreatic arteries that stem from the splenic, gastroduodenal, and superior mesenteric arteries. The major contributor is the splenic artery.

Pancreatic veins are responsible for draining deoxygenated blood from the pancreas. The anterior superior pancreaticoduodenal vein empties into the superior mesenteric vein, while the posterior variant empties into the hepatic portal vein. Both the anterior and posterior inferior pancreaticoduodenal veins drain into the superior mesenteric vein, while the pancreatic veins draining venous blood from the body and tail empty into the splenic vein.

Do you want to see the exact trajectory of the previously explained blood vessels and master their anatomy? Take advantage of the following resources! With our custom quiz you can test your newly acquired knowledge on the arteries of the pancreas.

Innervation

The pancreas receives involuntary innervation via the autonomic nervous system (ANS). Its parasympathetic innervation originates from the vagus nerve (CN X) and its sympathetic innervation from the greater and lesser splanchnic nerves (T5-T12). Both types of autonomic fibers travel until the celiac ganglion and superior mesenteric plexus, ultimately projecting onto the pancreas. 

Inside the organ, they carry nerve impulses to the acinar cells and the pancreatic islets. Parasympathetic fibers induce secretion from acinar cells, ultimately resulting in the release of pancreatic juice, insulin and glucagon. In contrast, sympathetic fibers cause vasoconstriction and inhibition of exocrine secretion, in other words, inhibition of pancreatic juice. In relation to hormonal release, sympathetic innervation stimulates the release of glucagon but inhibits that of insulin. 

Lymphatics

Lymph is drained from the body and tail of the pancreas via lymphatic vessels that empty into the pancreaticosplenic lymph nodes located along the splenic artery. The vessels draining the head empty into pyloric lymph nodes. Subsequently, lymph is transported to the superior mesenteric or celiac lymph nodeslymph nodes.

For more information about the lymphatics of the pancreas and a quiz testing your knowledge of the entire organ, take a look at the following resources:

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• Hepatopancreatic ampulla
• Pancreatic duct