Islets of Langerhans
What are the Langerhans Islands?
The pancreas is made up of different cell types. Between the glandular tissue there are about one million cell clusters, which are arranged island-shaped and are called Langerhans islands. They were named after the physician Paul Langerhans and have the task to regulate the blood sugar level via the hormones glucagon and insulin.
Anatomy & Construction
The Langerhans Islands are cell clusters that consist of about 2, 000 to 3, 000 cells. The islands make up about one to three percent of the mass of the pancreatic tissue and are more common in the tail area than in the head area. Altogether one differentiates between four endocrine island cell types: The B cells are responsible for the formation of insulin. They can be selectively displayed immunohistochemically and contain very typical secretion granules and a crystalline center in the electron microscope. The glucagon is formed by the A cells, which are located in the outer area of the islands. They are larger than the B cells and account for about twenty percent of the islet cells.
If the glucose concentration in the blood drops, the A cells release glucagon. As a result, the glucose release or the glucose synthesis is increased and the blood glucose concentration increases. The D cells produce somatostatin, which inhibits the secretion of glucagon and insulin. The fourth group are the PP cells that make up the pancreatic polypeptide, thereby inhibiting pancreatic secretion. An island is supplied by one to three island arterioles. These can split in the outer area of the island or in the center in capillaries. As a result, the islands are supplied from the depth or from the surface. In addition, there are several laxative vessels through which the blood leaves the islands. These are called insuloacinar portal veins and enter the exocrine acinar cells.
Function & Tasks
In the Langerhans Islands, glucagon and insulin are formed, both of which are important for carbohydrate metabolism. With the help of insulin, the blood sugar level is lowered. If carbohydrates are absorbed, insulin is released, which promotes the utilization or uptake of glucose. When insulin is formed, the proinsulin splits into a C-peptide and an insulin molecule, both of which are released in the same proportion. This can be used to determine whether the body's own insulin is still produced. In addition, insulin also affects the appetite sensation and prevents fat tissue from being broken down.
If the insulin is insufficient, very high triglyceride levels are detectable. If there is a complete insulin deficiency, the body is flooded with fatty acids and severe metabolic disorders occur. The antagonist to insulin is the glucagon. Glucagon promotes glycogen breakdown in the liver and stimulates insulin secretion. If the blood sugar level drops or if you take a very high-protein meal, glucagon is released. As a result, glucose is released in the liver, so that the blood glucose level increases again. This mutual glucagon and insulin synthesis causes the blood glucose level to normalize very quickly.
A very common disease is diabetes mellitus. Diabetes is characterized by high blood sugar and sugar in the urine. In addition, patients complain of severe thirst, blurred vision, itching, skin infections and weight loss. High levels of blood sugar cause damage to the blood vessels and cholesterol and fats are deposited, increasing the risk of an infarction. In the eye it comes to worsening to blindness and the kidney can completely fail. In addition, the nerves on the feet and legs can be damaged, so you often do not notice minor injuries.
When the wounds become infected, ulcers develop that lead to a so-called diabetic foot. In Type 1 diabetics, very little or no insulin is released because the B cells are destroyed by the immune system. In type 2 diabetics, the body can not respond adequately to the released insulin and insulin production diminishes. This type is also called "adult onset diabetes" because it usually occurs only at the age of about 56 years, but it can also occur in overweight people or in people with elevated blood lipids. Another form of diabetes can also occur during pregnancy, as there is insensitivity to insulin, which is hormonal.
As a result, a morbid glucose tolerance occurs, but disappears after pregnancy again. Secondary diabetes develops as a result of other diseases such as pancreatic disease, hyperthyroidism, infection, or long-term medication. Insulin secretion can be restored by transplanting isolated islet cells. For this purpose, one isolates islet cells from the pancreas of a donor and cleans them in a very complex process.
Thereafter, the cells are flooded into the liver with the aid of a catheter, where they resume the regulation of blood sugar. So that the foreign tissue is not repelled, an immunosuppression (suppression of the defenses by drugs) is required. Many diabetics can thus do without injected insulin, but the duration of success so far is relatively limited. Many transplant patients need insulin again after about one year, so islet cell transplantation is still not a routine procedure in diabetology.
Typical & common diseases of the pancreas
- Pancreatitis (pancreatitis)
- Pancreatic cancer (pancreatic carcinoma)
- Diabetes mellitus