Islet of Langerhans: They are insulin-producing tissues. It was discovered by Paul Langerhans in 1869. These cells are in groups and look like islands in the pancreas. There are about one million islets in a healthy adult human pancreas. It weighs about 1 to 1.5 grams. The maximum Islets of Langerhans are found in tail region of the pancreas.

As already stated, the pancreas has about 1 million islets of langerhans. An islet may have few dozens to several thousand of cells. They are scattered irregularly throughout the pancreas, but most densely in the tail region. There are three major types of islet cells - alpha cells, beta cells and delta cells. Beta cells are situated at the core of the islet. Alpha cells are situated peripherally next to the beta cells. Delta cells are situated more peripherally next to alpha cells, Fig. The beta cells have the shape of a truncated pyramid. The alpha cells look like columns. The delta cells are dendrite in shape. All these cells have lot of secretory granules in them. Beta cells constitute about 60 percent of total islet cells. Alpha cells and delta cells constitute about 25 percent and 10 percent of total islet cells respectively