What Is the Head of Pancreas?

The pancreas is a large gland in the human body that is second only to the liver. It is behind the stomach and corresponds to the height of the first and second lumbar vertebrae. Its long axis is slightly curved and is located in front of the posterior abdominal wall. The pancreas is soft and dense, grayish red, weighing about 65 to 75 grams, and has a triangular shape. It is divided into the pancreatic head, pancreatic body, and pancreatic tail.

Chinese name: pancreatic
Foreign name: pancreas
Radicals: month

External strokes: 6
Pinyin: yí
Wubi 86: : EGXW
Wubi 98: EGXW

Pancreas

Basic meaning of pancreas

1. One of the glands in the human or higher animal, in the lower back of the stomach (also known as "pancreas"): ~ fluid, ~ lipase, ~ protease, ~ amylase, ~ child (a. B. Soap).

Pancreas detailed meaning

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1. Pancreas A large compound digestive gland, located in front of the first lumbar vertebra and behind the stomach. Post-duodenal communication

Pancreas common phrase

Insulin

[insulin] Langerhan Island (islet) secreted a kind of protein pancreatic hormone, especially indispensable for carbohydrate metabolism. Commodities are often extracted and crystallized from the pancreas of cattle or pigs for the treatment and control of diabetes

Pancreas

[pancreas] See "Pancreas"

Pancreatic juice

[pancreatic juice] Clear alkaline pancreatic secretion containing at least three different enzymes. Trypsin, pancreatic amylase, and lipase or their precursors are mixed with bile sweat and intestinal fluid after flowing into the duodenum to further digest food that has been partially digested by saliva and gastric enzymes

4. Pancreatic lipase

[pancreatic lipase; steapsin]

5. Pancreas

(1) [pancreas of pigs, sheep, etc.] []: Pancreas of pigs, sheep, etc.

(2) [soap]

Pancreas is the second largest digestive gland of the human body. It is located behind the stomach, transverse to the posterior abdominal wall, and spans in front of the first and second lumbar vertebrae.

The pancreas is long, soft, grayish red or light red, and can be divided into three parts: head, body, and tail. The pancreatic head swell is located on the right side and is surrounded by the duodenum. The end of the pancreatic duct penetrates into the duodenal wall, meets the common bile duct, and opens in the duodenal papilla.

The pancreas is divided into two parts: exocrine glands and endocrine glands. Exocrine glands consist of acinar (glandular cells) and glandular ducts. The acinar secretes pancreatic juice, and the glandular duct is the channel through which the pancreatic juice is discharged. Pancreatic juice contains sodium bicarbonate, trypsin, lipase, and amylase. Pancreatic juice flows into the pancreatic duct through various levels of catheters. The pancreatic duct and common bile duct open together in the duodenum. Pancreatic juice is drained through the pancreatic ducts into the duodenum.

Pancreatic juice contains a variety of digestive enzymes, which can digest proteins, fats and sugars.

The endocrine glands are made up of islet cells of different sizes scattered between the exocrine glands. There are three types of islet cells: A, B, and D. Among them, islet A cells secrete glucagon, which can promote the breakdown of glycogen in liver cells, muscle fibers, etc. into glucose, and inhibit glycogen synthesis to increase blood sugar; the hormone secreted by islet B cells is called insulin, which directly enters the blood Lymph, which is mainly involved in regulating glucose metabolism. Insufficient insulin secretion can cause diabetes; D cells secrete somatostatin, which can inhibit the secretion of A and B cells to maintain insulin secretion in accordance with blood glucose concentrations.

Pancreas experiment: Section 71: HE staining of pig or bovine pancreas.

The pancreas parenchyma is divided into many leaflets, and there are lightly stained cell clusters between the acinars, namely islets.

The acinus is made up of cone-shaped cells with a round nucleus located slightly off the base in the center of the cell. The free end of the cell is stained with light purple, the bottom of the cell is stained with purple, and the bottom of the cell is stained with dark purple. Can secrete pancreatic juice. Vesicular heart cells, sacral ducts (single layer of flat epithelium), intralobular ducts (single layer of cubic epithelium), interlobular ducts (single layer of columnar epithelium), and pancreatic ducts (high columnar epithelium).

Pancreas

The head of the pancreas is located on the right side of the second lumbar vertebra and is enclosed in a C -shaped groove in the duodenum. The left part of the pancreas is called the hook process. There is a portal vein and common bile duct behind the head of the pancreas. The pancreatic body is the middle part of the pancreas, the front is adjacent to the stomach, and the back crosses the front of the first lumbar vertebra, and contacts the abdominal aorta, inferior vena cava, left kidney, and left adrenal gland. The tail of the pancreas extends to the upper left and contacts the spleen hilum. The pancreas has a long columnar shape and is divided into three parts: head, body, and tail. The head of the pancreas is wide and surrounded by the duodenum. The tail of the pancreas is blunt and thin, located at the upper left, with the pancreas body between the head and tail. The parenchyma of the pancreas is divided into endocrine and exocrine parts, and the exocrine part secretes pancreatic juice, which is discharged into the duodenum through the pancreatic duct and participates in digestion. The endocrine area is islets, which are small cell clusters scattered in the parenchyma. Insulin secreted by the islets can regulate blood sugar concentration and increase fat synthesis in the liver. Insulin inhibits the breakdown of proteins and promotes protein synthesis, which is indispensable for human growth and development. If insulin is lacking, the growth hormone secreted by the pituitary will not function, and growth and development will be impeded. The islets also secrete glucagon, which promotes the breakdown of glycogen and fat and urea production, and has a strong heart, inhibits gastric and intestinal peristalsis, and increases renal blood flow.

Pancreatic anatomy

The pancreas is usually not visible on a supine abdominal plain film. The surrounding retroperitoneal fat is not very helpful in understanding its size and shape. Although its location is just below the stomach, unless the pancreatic pseudocysts, abscesses, and tumors have become very large, changes in the outline of the gastric vesicles do not reflect an increase in the volume of the pancreas. Moreover, due to the close relationship between the pancreas and the common bile duct and spleen vein, even small pancreatic lesions can show obvious clinical and laboratory manifestations before X-ray examination. However, abnormalities of the pancreas, especially acute and chronic inflammation, can show reliable plain film signs of the pancreas itself and surrounding tissue structures. The special shape of gas accumulation, displacement of organs, and calcification are often easily found on plain radiographs. Careful observation of the performance of these plain films can help to quickly diagnose or choose the best next imaging method.

Pancreatic histology

Tissue structure The surface of the pancreas is covered with a thin layer of connective tissue envelope. A small amount of connective tissue extends into the gland and divides the parenchyma into many leaflets. The substance consists of a ducted exocrine part and a ductless endocrine part. The exocrine part occupies most of the pancreas and consists of two parts, acinus and duct. Acinars vary in size and are vesicular or tubular. Glandular epithelial cells are cone-shaped, with a circular nucleus at the base of the cell, and cytoplasm at the top contains secretory particles. In the acinar cavity, 2 to 3 oblate heart cells and sacral ducts were continuous. Catheters are divided into sacral ducts, intralobular ducts, interlobular ducts, and pancreatic ducts. The sacral canal consists of a single layer of flat or low-cubic epithelium, the sacral canal merges into the intralobular duct, and its wall consists of a cubic epithelium. The intralobular duct exits the leaflet and enters the interlobular connective tissue into the interlobular duct. The epithelium of the tube wall increases into a short columnar shape, and finally enters the pancreatic duct. The tube wall is composed of tall columnar cells, sandwiched by goblet cells, and occasionally scattered endocrine cells. The endocrine section is a group of endocrine cells of various sizes and shapes scattered in the acinus to aggregate into islets. The islet cells are arranged into irregular and anastomosing cell cords. There are abundant capillaries and sinuses between the cords. The insulin and glucagon secreted by the cells enter the intercellular space or the connective tissue space around the blood vessels, thereby reaching the circulatory system.

Pancreatic Pancreatic Juice Secretion and Regulation

The organic components in pancreatic juice include albumin, globulin, and enzyme protein. The protein concentration is between 0.1% and 10%. As pancreatic enzyme secretion increases, the protein concentration in the pancreatic juice increases. Pancreatic juice contains enzymes that digest the three major nutrients of sugar, lipids, and proteins, most of which are secreted in the form of zymogens. An activator is required to convert them into enzymes before they can act on the substrate (see table). Therefore, under normal circumstances, trypsin does not digest pancreatic tissue itself.

Pancreatic juice is not secreted when fasting. Pancreatic fluid secretion is caused by eating, which is regulated by nerves and hormones.

Neuromodulation. The color, aroma, taste, shape and volume of food stimulate the body's receptors, which can cause pancreatic fluid secretion in a reflective way. The nerves that dominate the pancreas are the vagus nerve and splanchnic nerve.

hormone regulation. The main gastrointestinal hormones that stimulate pancreatic juice secretion are secretin and secretin. Secretin can stimulate S endocrine cells in the intestinal mucosa and release secretin. This hormone can stimulate pancreatic juice secretion through blood circulation and also stimulate acinar cells to secrete a small amount of pancreatin. Tryptase can stimulate I endocrine cells in the intestinal mucosa and release cholecystokinin-tryptase (CCK-P2). This hormone stimulates the pancreas through blood circulation, secretes pancreatin and promotes gallbladder contraction.

Pancreas Endocrine and Hormones

The endocrine part of the pancreas is a cell cluster of different sizes and shapes, called islets, which mainly secrete a variety of hormones. The two main types are insulin and glucagon:

1.Insulin

The beta cells of the islets secrete insulin. Its effect is to lower blood sugar, which is the result of various effects of insulin on sugar metabolism, such as promoting the carrier transport process of glucose, making it easy for sugar to pass through the cell membrane; increasing the activity of hexokinase or glucokinase; promoting the further development of glucose 6-phosphate Oxidation, which enhances the use of sugar; increases the synthesis of glycogen; inhibits gluconeogenesis. As a result, the blood glucose concentration decreased significantly. In addition, insulin can inhibit the release of free fatty acids from adipose tissue and promote fat synthesis, as well as protein and nucleic acid synthesis.

Insulin must bind to cell membrane receptors to function. Most cells in the body, such as liver, fat cells, skeletal muscle, cardiac muscle, lymphocytes, brain, adrenal gland, ovary, uterine cells, etc. have insulin receptors. The number and affinity of insulin receptors on target cells can vary significantly under different circumstances. If insulin secretion increases after eating, its receptor number and affinity decrease. The number and affinity of the receptors returned to normal after fasting.

In the absence of any external stimulus, insulin is continuously secreted. Glucose is the most important and frequently occurring stimulus. After the administration of glucose, the insulin secretion reached a peak within a few minutes, and the administration of glucose was stopped, and the insulin quickly returned to normal levels. Fake feeding can cause insulin secretion and can form a conditioned reflex. Insulin secretion requires calcium ions, and as intracellular Ca2 + increases, insulin secretion increases.

2.Glucagon

Glucagon is also known as glucagon or anti-insulin or insulin B. It is a hormone that is secreted by insulin from the islet alpha cells of the vertebrate pancreas. It is relatively resistant to insulin and plays a role in increasing blood sugar. In 1953, it was separated and precipitated to obtain crystals. It is a single-chain peptide (molecular weight of about 3500) consisting of 29 amino acid residues with N-terminal histidine as the starting point and C-terminal threonine as the ending point. There is no SS bond in the molecule. Completely different from insulin. The structure of this compound has been confirmed by recent chemical synthesis. The initial process of glucagon is to specifically bind to the receptor present on the cell membrane of the target cell, to activate adenylate cyclase, and cyclic AMP becomes the second messenger to activate phosphorylase and promote glycogen decomposition. Human glucagon is a linear polypeptide consisting of 29 amino acids with a molecular weight of 3485. It is also cleaved from a large molecule precursor. The concentration of glucagon in serum is 50-100ng / L, and the half-life in plasma is 5-10min. It is mainly inactivated in the liver and degraded by the kidney.

(A) the main role of glucagon

Contrary to the role of insulin, glucagon is a hormone that promotes catabolism. Glucagon has a strong role in promoting glycogen decomposition and gluconeogenesis, which significantly raises blood sugar. A 1 mol / L hormone can quickly decompose 3 × 106 mol / L glucose from glycogen. Glucagon activates the phosphorylation enzymes of liver cells through the cAMP-PK system and accelerates glycogen breakdown. Enhancement of gluconeogenesis is because hormones accelerate amino acids into liver cells and activate enzymes involved in the gluconeogenesis process. Glucagon can also activate lipase, promote lipolysis, and at the same time strengthen the oxidation of fatty acids and increase the production of ketone bodies. The target organ for glucagon to produce the above-mentioned metabolic effects is the liver. When the liver is excised or the blood flow is blocked, these effects disappear.

In addition, glucagon can promote the secretion of insulin and islet somatostatin. Pharmacological doses of glucagon can increase cAMp content in myocardial cells and increase myocardial contraction.

(B) Regulation of Glucagon Secretion

There are many factors affecting glucagon secretion, and blood glucose concentration is an important factor. When the blood glucose decreases, the secretion of glucagon increases; when the blood glucose increases, the secretion of glucagon decreases. The effect of amino acids is opposite to glucose, which can promote glucagon secretion. Protein meal or intravenous injection of various amino acids can increase glucagon secretion. The increase of amino acids in the blood promotes insulin release on the one hand, which can reduce blood sugar, and stimulates glucagon secretion at the same time, which has certain physiological significance for preventing hypoglycemia.

Insulin can indirectly stimulate glucagon secretion by reducing blood glucose, but islet ratios secreted by B cells and somatostatin secreted by D cells can directly affect adjacent A cells and inhibit glucagon secretion.

Insulin and glucagon are a pair of hormones with opposite effects, and they form a negative feedback regulation loop with blood glucose levels. Therefore, when the body is in different functional states, the molar ratio (I / G) of insulin to glucagon in the blood is also different. Generally, the ratio of I / G is 2.3 under the condition of overnight fasting, but the ratio can drop below 0.5 when starving or exercising for a long time. The smaller ratio is due to reduced insulin secretion and increased glucagon secretion, which is beneficial for glycogen breakdown and gluconeogenesis, maintains blood glucose levels, adapts to the needs of the heart and brain for glucose, and facilitates lipolysis and enhanced fatty acids Oxidative energy. In contrast, the ratio can rise to more than 10 after ingestion or sugar load, which is due to increased insulin secretion and reduced glucagon secretion. In this case, the islet-comparison effect is dominant.