What is the target cell of insulin

This is how insulin works

Like all internal organs, the pancreas also receives chemical, e.g. hormonal, control signals, as well as those of the vegetative, non-voluntarily controllable nervous system. The nerve fibers shown here belong to the sympathetic nervous system, which, in addition to the parasympathetic nervous system, is part of the autonomic nervous system. The sympathetic nerve fibers come from the spine and run along arteries to the internal organs. Your nerve nodes (ganglia) are located here in the area of ​​the 1st lumbar vertebra just above the pancreas around the abdominal artery (aorta abdominalis) and the arterial branches that branch off from it. They are connected to one another by numerous nerve fibers. In this way, they form a ray-like network of nerve fibers and ganglia, which, due to its appearance, was previously referred to as the solar plexus or solar plexus. It is known to be an extremely sensitive region. A blow to the solar plexus can cause an adult to become unconscious.

The pancreas is composed of many small lobules. The main part of a lobule is made up of glandular tissue that produces the digestive juice. It mainly contains digestive enzymes to break down proteins, fats and sugars, the amount of which fluctuates depending on the food being eaten. The secretion flows into numerous small ducts that eventually flow into the central pancreatic duct.

The pancreatic lobules, which are abundantly supplied with blood vessels and nerves, mainly consist of Glandular tissue. Its cells make pancreatic secretions with digestive enzymes. The hormone-producing cells of the pancreas are embedded in the glandular tissue like islands. These cell groups are named after the German physician Paul Lagerhans (1847-1888), also as Langerhans Islands designated. They occur mainly in the area of ​​the body and tail of the pancreas, rarely in the head of the pancreas.

The pancreatic duct (ductus pancreaticus), which runs from tail to head through the entire pancreas, feeds the digestive secretions formed in the pancreatic lobules to the intestine with enzymes. It flows into the small intestine with the so-called Vater’s papilla. Shortly before the mouth, it often unites with the main bile duct, in which the other important digestive secret, the bile from the liver, flows to the intestine. It is less common that both passages lead separately into the intestine.

The main bile duct opens into the small intestine with a small bulge (papilla) in the intestinal mucosa. This mouth is called the Vater'sche papilla after the German anatomist Abraham Vater (1684 - 1751). Here, the bile duct is surrounded by a ring-shaped sphincter that is permanently contracted, preventing bile and pancreatic secretions from flowing out when the bowel is empty. As soon as the chyme from the stomach reaches the small intestine, a hormone in the intestinal wall causes the sphincter muscle to open and the digestive juices to drain into the intestine.

The entirety of all Langerhans Islands is often referred to as the island organ. Each islet of Langerhans contains about 3000 islet cells, which are divided into A, B and D cells. Most, around 75 to 80 percent, are B-type. They form the important metabolic hormone insulinthat promotes the absorption of sugar from the blood into the body's cells. The A cells, the proportion of which is about 20 percent, form Glucagon, the antagonist of insulin. When the blood sugar level is low, glucagon supports the breakdown of energy reserves, especially from the liver. Both hormones are released directly into blood vessels within the lobules, known as endocrine gland function (arrows). About 5 to 10 percent of the cells are D-type. They make the hormone Somatostatinwhich has a regulating effect on the A and B cells and dampens their hormone production.

The exocrine gland cells of the pancreas sit in berry-shaped gland end pieces (acini), from which the lobules are built. One of the small branches of the pancreatic duct begins in each end piece. If necessary, the glandular or acinar cells release the slightly basic digestive secretion with the digestive enzymes into the duct, i.e. not into the bloodstream or directly into the tissue (arrows). This is known as exocrine gland function. The production of the secretion starts just a few minutes after eating and lasts for a few hours. It is stimulated by nerve signals and chemically by the hormone cholecystokinin from the intestinal mucosa when food reaches the stomach or intestines.