What is the pancreas? The pancreas is a long, flat gland located deep in the abdominal cavity. Because it is difficult to feel the pancreas in daily life, people do not know much about the pancreas compared to other organs. However, the pancreas is a very important part of the digestive system and blood sugar regulation. The pancreas is located deep in the abdominal cavity, part of it is located between the stomach and the spine, and the rest is located in the duodenal ring (the first part of the small intestine). To visualize the location of the pancreas, try this: touch your right thumb to your little finger, put the other three fingers together and straighten them, then place your hand in the center of your stomach, below your rib cage, with your fingers pointing to the left. Then your hand is the approximate shape and location of the pancreas. Because of the deep location of the pancreas, pancreatic tumors are difficult to touch. This explains why pancreatic cancer does not show symptoms until it grows large enough to affect the function of the pancreas or to affect surrounding organs such as the stomach, duodenum, liver and gallbladder. Figure 1 Location of the pancreas Components of the pancreas Your doctor may mention several anatomical components of the pancreas when discussing your condition with you. Pancreatic tumors in different locations will have different symptoms as well as different treatment options. The pancreas is divided into five parts. Figure 2 Anatomy of the pancreas Two functions of the pancreas The pancreas is a mixture of two glands. The majority of the pancreas is made up of exocrine cells that secrete digestive enzymes that help the body digest food. These exocrine cells release enzymes into progressively larger lumens (ducts) inside the pancreas, which eventually form the main pancreatic duct, which runs the length of the pancreas and drains digestive enzymes into the duodenum (the first part of the human small intestine). The second major function of the pancreas is endocrine function, and the endocrine pancreas consists of small island-like cells called islets of Langerhans. These endocrine cells do not excrete enzymes into the pancreatic ducts, instead they release hormones such as insulin or glucagon (a hormone that raises blood glucose) into the circulation, and these hormones are involved in the regulation of blood glucose in the body. Figure 3 Function of the pancreas Alveolar cells are the exocrine cells of the pancreas that produce and transport enzymes that are excreted into the duodenum to participate in the digestion of food. Figure 4 Structure of the alveolar cells Langerhans islet cells Langerhans islet cells are endocrine cells in the pancreas that produce and secrete insulin or glucagon (a hormone that raises blood sugar) into the circulation. Together, insulin and glucagon maintain a steady level of blood sugar, which is the body’s source of energy. A full understanding of the two functions of the pancreas has two important implications: 1. The enlargement of pancreatic tumors has an important impact on both functions: when the tumor blocks the duct of pancreatic enzymes discharge, the patient will experience pancreatitis and abdominal pain because the digestive enzymes of the pancreas cannot be discharged to the intestine at this time, but instead have a digestive effect on the pancreas itself; and at this time, the patient will have diarrhea because the digestive enzymes cannot digest food; meanwhile If the tumor destroys the function of pancreatic islet, diabetes will appear. 2. Pancreatic tumors may originate from cells of both functions: most of the pancreatic tumors originate from exocrine cells, and under the microscope they are similar to normal pancreatic ducts, so they are called ductal adenocarcinoma or adenocarcinoma (which is what we usually call pancreatic cancer); while the relatively rare tumors that originate from endocrine cells are called pancreatic neuroendocrine tumors or islet cell tumors. The pancreas participates in digestion with surrounding organs The pancreas is an important part of the digestive system, and the order of digestion is often changed after surgery for pancreatic cancer, so it is important to understand the order in which food is normally excreted in the digestive tract. After the food is swallowed by the mouth, it enters the stomach through the esophagus (a tubular organ that connects the mouth and the abdomen). In the abdomen, the esophagus discharges the food into the stomach, where the acidic gastric juice can digest and break down the food. The duodenum is followed by the rest of the small intestine, called the jejunum and ileum, where food continues to be digested. At the end of the ileum food enters the large intestine and eventually forms feces that is excreted through the anus. Figure 5 Pancreas and surrounding organs (stomach, duodenum, gallbladder) Bile It is important to understand the function of bile because in pancreatic cancer the drainage of bile is often impaired and the drainage of bile is altered after surgery for pancreatic cancer. Bile is a yellow-green liquid involved in fat digestion. After being synthesized by liver cells, bile passes through the bile duct to join the cystic duct of the gallbladder to form the common bile duct, crosses the head of the pancreas to join the pancreatic duct to form the tepid potbelly (a segment of duct that widens before entering the duodenum), and then enters the duodenum (the direction of bile drainage is shown by the green arrow). Figure 6 Function and drainage direction of bile Pancreatic juice The pancreatic juice in the pancreatic duct is produced by the pancreatic alveoli. The main pancreatic duct of the pancreas, which usually has many branches, joins with the bile duct at the head of the pancreas to form the spent pot belly, after which it enters the duodenum. As with bile, pancreatic cancer can block the drainage of pancreatic fluid, and likewise the drainage of pancreatic fluid changes after pancreatic surgery (the direction of pancreatic fluid drainage is shown by the black arrow). Figure 7 Function of pancreatic fluid and direction of drainage