Pancreatic beta cell is a type of cell in the pancreas that makes insulin. The pancreas is a fish-shaped organ that stretches across the back of the abdomen behind the stomach. Within the pancreas there are areas that are called the islets of Langerhans. The beta cells constitute the predominant type of cell in the islets. The beta cells are particularly important because they make insulin. Degeneration of the beta cells is the main cause of type I (insulin-dependent) diabetes mellitus. The pancreas is an organ that is part of the digestive system. It sits behind and below the stomach in the back of the abdominal cavity. It has two main functions: making digestive enzymes that help break down the proteins in your food, and producing the hormone insulin, which helps regulate your blood sugar levels.