The pancreas is a glandular organ in the abdominal cavity that is part of the digestive and endocrine systems. It consists of exocrine and endocrine cells that work together to maintain digestion and blood sugar levels. Acinar cells are exocrine cells arranged into clusters called acini. These cells secrete large volumes of enzyme-rich, alkaline digestive juices. The islets of Langerhans are clusters of endocrine cells scattered throughout the pancreas. There are four types of commonly known endocrine cells. Each of these secretes hormones involved in blood glucose regulation. Alpha cells produce glucagon, which stimulates the liver to release stored glucose and raises blood sugar levels. Beta cells produce insulin, which promotes glucose uptake by the body's cells, lowering blood sugar levels. Delta cells produce somatostatin, also known as the growth hormone-inhibiting hormone, which inhibits insulin and glucagon release. Pancreatic polypeptide or PP cells produce pancreatic polypeptides, which control the rate of nutrient uptake in the intestines.