The pancreas, formed by the primary intestinal cells of the endoderm, has two parts - the exocrine gland, occupying 98% of the whole body of the gland. And pancreatic islets, or islets of Langerhans - the endocrine part, located in small inclusions on the surface of the gland.
The exocrine department is responsible for the processes occurring in the duodenum, as well as the production of gastric juice and its saturation with enzymes that promote the breakdown of carbohydrates, proteins and fats.
Endocrine part produces hormones of carbohydrate synthesis.
Hormones synthesized by the pancreas
The endocrine department is involved in the synthesis of two different types of glandular cells, which are called insulin and glucagon. Synthesis of glucagon is produced by alpha cells, and beta cells participate in the production of insulin. In addition to alpha- and beta-cells, pancreatic islets contain another type - delta cells, which promote the production of somatostatin, an analogue of the hormone produced by the hypothalamus.
Insulin, as a polymeric hormone, is two polypeptide yarns connected by a pair of disulfide bonds. It is formed as a result of the action of beta-cell protease on low-active proinsulin, produced by the pancreas.
Regulation of secretory activity
There are two secretory types of insulin - stimulated and basal.
With the basal type, the hormone enters the bloodstream in the absence of stimuli. For example, on an empty stomach, at indicators of a level of sugar in the analysis of blood at practically healthy person no more than 5,5 mmol / l, and insulin level makes 69 mmol / l.
The stimulated type of secretion is caused by exogenous sends, such as amino acids or glucose metabolites that affect calcium exocytosis in the intake of insulin and C-peptide into the blood. The secretory function of the hormone of the pancreas is the stimulation of the action of amino acids, in particular leucine or preparations based on sulfonylureas.
There is a short, or initial stage of insulin stimulation and a long or slow stage. The short stage involves the release into the blood of the hormone enclosed in the granule. The slow phase is characterized by the synthesis of the hormone itself.
Effect and role of hormones
Gastric juice directly affects the exocrine activity of the pancreas. Its functionality depends on the quantitative content of hydrochloric acid in the liquid fraction of the secretion of the gland. It depends on the activity of secretion by the small intestine through the cell membrane of secretin and pancreosimin, as special substances that affect the synthesis of enzymes contained in pancreatic juice.
The use of medications such as vitamin A, morphine, magnesium sulfate, pilocarpine, stimulating the pancreas, can lead to increased secretory activity. Atropine and histamine lead to inhibition of its functions.
The intrasecretory role of the pancreas in the production of insulin and glucagon is responsible for regulating the process of carbohydrate and lipid metabolism, as well as the process of adsorption of glucose from the blood by tissues, fixing the quantitative glycogen index in the liver cells and reducing the level of lipemia. Glucagon promotes suppression of glucose adsorption from the blood plasma.
The main hormonal function is the synthesis of lipocaine, or lipotropic substance that blocks the degeneration of liver fat cells.
Lack of hormones in the pancreas
Hormonal failure caused by a lack of hormones in the human body can be associated with many causes, including congenital deficiencies.
Insulin deficiency leads to such an unpleasant disease as diabetes. With an excess of the hormone of the pancreas, there is a process associated with an increase in glucagon content, a decrease in the concentration of sugar in the blood plasma, and an increase in the content of adrenaline. Decreased insulin secretion and an increase in glucagon leads to hypoglycemia - suppression of glucose utilization processes by liver cells.
The deficiency of somatostatin, synthesized by delta-cells, of the somatostatin pancreas, an analog of the growth hormone produced by the pituitary, leads to inhibition of the body's internal functions with suppression of developmental processes and metabolic disorders.
Isolation of insulin by pancreas
Insulin is the hormone responsible for reducing the sugar content in the blood plasma and affecting fat metabolism in tissues.
The primary product of beta-cell synthesis is proinsulin. It is not a hormone and carries a biological activity. Its transformation into insulin occurs due to the Golgi complex - intracellular structure with the presence of specific enzymes. After the proinsulin is modified into insulin, it is again absorbed by the beta-cell. In it, the hormone is subjected to the process of granulation and enters the vault, from which it can be extracted in case of an acute shortage of it in the body.
Such a need arises every time with an elevated sugar content in the blood plasma. The role of insulin pancreas is to increase the permeability of the cell membrane for glucose with active absorption of the latter. It helps transform excess sugar into glycogen, and deposits it in muscles and liver. Due to the action of the hormone of the pancreas, the level of sugar in the blood plasma is significantly reduced.
What is behind the increased levels of insulin?
High insulin values in blood tests indicate that the body undergoes low resistance to excessive amounts of the hormone. This may be due to the exclusion of receptors responsible for carbohydrate metabolism. As a result, a disease develops, such as type 2 diabetes, or non-insulin dependent diabetes mellitus, in which the pancreas produces excess hormone, and the internal receptors do not respond to it: carbohydrates that come with food are not absorbed by the body, and the sugar level in the blood plasmagives good results.
Insulin injections are contraindicated in this type of diabetes, because the pancreas produces hormone in excess. The most unpleasant symptom in atypical diabetes is debilitating thirst, since excess glucose absorbs intracellular moisture, causing dehydration of the body.
Factors affecting the release of insulin
The pancreas of a healthy person is a very subtle instrument for tuning the entire body. She reacts very sensitively to the changes caused by the glucose in the blood, releasing a large amount of insulin with an excess of sugar and reducing it with its lack.
Diabetes leads to impaired pancreatic functions with oppression of the islets of Langerhans - the endocrine gland. Therefore, there are contraindications to the consumption of sugar-containing foods saturated with easily digestible carbohydrates, such as sweets, chocolate, honey or jam, as well as sugar, leading to depletion and further death of insulin-synthesizing beta cells.
Glucagon - a hormone synthesized by the pancreas
At the molecular level is a polypeptide consisting of one filament with a mass of 3,500 daltons. Glucagon is synthesized by alpha cells of the endocrine department. Mucous membrane of the intestine is entero-glucagon, being synergist of adrenaline, it functions directly in the cells of the liver. Its realization is carried out through cyclic AMP and adenylate cyclase. The pancreatic hormone is responsible for controlling the rate of lipolysis, as well as glycogenolysis of the liver.