islet of Langerhans cell
Meaning of islet of Langerhans cell: Beta and alpha cells sit close enough to argue with each other, which is how blood sugar is held within a narrow band.
Definition of islet of Langerhans cell
An islet of Langerhans cell is any of the hormone-producing cells clustered in the pancreatic islets, small rounded groups of tissue embedded among the digestive bulk of the pancreas. Several distinct types sit side by side within each cluster, the commonest making insulin and the next most numerous making glucagon. Their products pass straight into the bloodstream rather than into the gut.
Which cells does an islet contain?
| Cell type | Hormone made | What the hormone does |
|---|---|---|
| Beta cell | Insulin | Moves sugar from blood into cells for use or storage |
| Alpha cell | Glucagon | Prompts the liver to release its stored sugar |
| Delta cell | Somatostatin | Damps down the release of both of the above |
| PP cell | Pancreatic polypeptide | Influences appetite and digestive secretion |
| Epsilon cell | Ghrelin | Signals hunger |
Beta cells make up most of a typical islet, and their destruction by the immune system is what produces type 1 diabetes. All the islets together account for only a small fraction of the weight of the pancreas, which is otherwise given over to making digestive juice.
How does a cluster of cells hold blood sugar steady?
By keeping opposing signals in direct contact. After a meal the beta cells register the rise in blood sugar and release insulin, which drives that sugar into muscle, fat and liver. Between meals and overnight the alpha cells release glucagon, which tells the liver to break its store down and push sugar back out. The two cell types sit within reach of each other and each hormone influences the neighboring cells directly, so the cluster behaves as a single control loop rather than as two separate glands. Blood passes through an islet before reaching the surrounding digestive tissue, so these hormones reach it first.
Why does the name cause confusion?
Because two unrelated things carry it. The islets are named for the physician who first described them in the pancreas. That same physician also described a population of immune cells in the skin, and those are called Langerhans cells. The two share nothing but a name: one group makes hormones in an abdominal gland, the other patrols the skin as part of the immune defenses. The disorder Langerhans cell histiocytosis is a disease of the skin type and has no bearing on the pancreas or on blood sugar. Tumors that do arise from islet cells were long called islet cell tumors and are now grouped with the pancreatic neuroendocrine tumors.
Also known as
Used in a sentence
The specimen showed preserved islet of Langerhans cell architecture within the pancreatic tissue.
Good to know
The islets of Langerhans in the pancreas and the Langerhans cells of the skin are unrelated despite sharing a name, and Langerhans cell histiocytosis is a disorder of the skin cells with no bearing on blood sugar control.
Word origin
Where “islet of Langerhans cell” comes from
Islet reaches English through French from the Latin insula, meaning island, describing clusters of hormone-making cells set like islands within the surrounding digestive tissue. The rest of the name honors the physician who described them.