Paul Langerhans (1847–1888) was the first to provide a detailed description of microscopic pancreatic structures in the late 1860s. He noticed unique polygonal cells in the pancreas. It was not until 1893 that G.E. Laguesse discovered that the polygon-shaped cells were the endocrine cells of the pancreas that secreted insulin.
The parts of the pancreas: 1 = Uncinate process; 2 = Head; 3 = Main pancreatic duct; 4 = Hepatopancreatic ampulla; 5 = Common bile duct; 6 = Accessory pancreatic duct; 7 = Neck; 8 = Body; 9 = Tail. The Islet of Langerhans includes 10 = Alpha cell; 11 = Beta cell; 12 = Delta cell. Anatomical Chart Co.