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Pancreas
Last reviewed: 20.11.2021
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The pancreas (pancreas) has an elongated shape, a gray-pink color, is located in the retroperitoneum. The pancreas is a large digestive gland of mixed type. It has simultaneously exocrine part with typical secretory departments, protocol apparatus and endocrine part. As an exocrine gland, it produces 500-700 ml of pancreatic juice daily, which enters the lumen of the duodenum. Pancreatic juice contains proteolytic enzymes, trypsin, chymotrypsin and amylolytic enzymes (lipase, etc.). The endocrine part of the gland in the form of small cell clusters (pancreatic islets) produces hormones (insulin, glucagon, etc.) that regulate carbohydrate and fat metabolism.
The length of the pancreas in an adult is 14-18 cm, width - 6-9 cm, thickness - 2-3 cm, its mass is 85-95 g. The gland is covered with a thin connective tissue capsule. The gland is located transversely at the level of I-II lumbar vertebrae. The gland of the gland lies slightly higher than its head.
Behind the pancreas are the spine, the aorta, the lower hollow and left renal veins. In front of the gland is the stomach. The pancreas is secreted with a head, body and tail.
The head of the pancreas (caput pancreatis) is on top right and bottom covered by the duodenum. The head is slightly flattened in the anteroposterior direction. On the border between the lower part of the head and the body there is a deep cut of the pancreas (incisura pancreatis), in which the superior mesenteric artery and vein pass. The posterior surface of the head of the pancreas is attached to the right renal vein, and closer to the median plane - to the initial part of the portal vein. Ahead of the gland is the right side of the transverse colon.
The body of the pancreas (corpus pancreatis) is prismatic in shape, it has anterior, posterior and lower surfaces. The front surface (facies anterior) is covered with a parietal peritoneum. On the border of the body of the gland with its head there is a bulge anteriorly - the so-called gland tuber (tuber omentale). The posterior surface (facies posterior) is attached to the spine, large blood vessels (inferior vena cava and aorta), the celiac plexus. The lower surface (facies inferior) is narrow, partly covered by the peritoneum, separated from the anterior surface by the anterior edge of the gland. To the upper edge of the gland adjoining the splenic artery and vein.
The tail of the pancreas (cauda pancreatis) is directed to the left, where it touches the visceral surface of the spleen, below its gates. Behind the tail of the gland are the left adrenal gland, the upper part of the left kidney.
The parenchyma of the gland is divided into lobules by connective tissue interlobular septa (trabeculae) that extend inward from the capsule of the organ. In the lobules are the secretory sections resembling hollow sacs in the size of 100-500 microns. Each secretory department - pancreatic acinus (acinus pancreaticus) consists of 8-14 cells - exocrine pancreatocytes (acinocytes), having a pyramidal shape. Secretory (acinous) cells are located on the basal membrane. From the cavity of the secretory department, the insertion grooves (diictuli intercalatus), lined with a single-layered flattened epithelium, begin. Insertion grooves give rise to the protocol apparatus of the gland. Insertion grooves pass into intralobular ducts (ductuli intralobulares), formed by a single-layered cubic epithelium, and then into interlobular ducts (ductuli interlobulares) passing through interlobular connective tissue septa. The walls of interlobular ducts are formed by a high prismatic epithelium and its own connective tissue plate. Interlobular ducts flow into the excretory duct of the pancreas.
The inferior duct (main) of the pancreas (ductus pancreaticus), or the virsung duct, goes into the thickness of the gland, closer to its posterior surface. The duct begins in the region of the gland's tail, passes through the body and head, takes on the course of smaller interlobular excretory ducts. The main duct of the pancreas flows into the lumen of the descending part of the duodenum, opens on its large papilla, previously connected with the common bile duct. The wall of the final section of the pancreatic duct has a sphincter of the duct of the pancreas (sphincter ductus pancriaticae), which is a thickening of the circular bundles of smooth muscles. Often, the pancreatic duct and the common bile duct flow into the duodenum separately at the apex of the large papilla of the duodenum. Other variants of the confluence of both ducts are possible.
In the area of the head of the pancreas, an independent additional duct of the pancreas (ductus pancreatis accesorius), or santorini in the duct, is formed. This duct opens into the lumen of the duodenum on its small papilla. Sometimes both ducts (main and additional) anastomose with each other.
The walls of the main and additional ducts are lined with a cylindrical epithelium. In the epithelium of the protocol apparatus of the pancreas there are goblet cells that produce mucus, as well as endocrine cells. Endocrine duct cells synthesize pancreosimine and cholecystokinin. In its own plate of the mucous membrane of the interlobular ducts, the additional and main ducts there are multicellular mucous glands.
Endocrine part of the pancreas
The endocrine part of the pancreas is formed by pancreatic islets (islets of Langerhans), representing accumulations of endocrinocytes. The islets are located mainly in the region of the tail, and less in the body of the gland. Pancreatic islets are round, oval, ribbon-shaped or star-shaped. The total number of islands is 0.2-1.8 million, the diameter of the island varies from 100 to 300 microns, the mass of all islets is 0.7-2.6 g. There are several varieties of endocrine cells forming islets.
[8], [9], [10], [11], [12], [13]
Innervation of the pancreas
The pancreas is innervated by the branches of the vagus nerves (mainly right), sympathetic nerves from the celiac plexus.
Blood supply to the pancreas
The pancreas is supplied with blood by means of such vessels: the anterior and posterior pancreatic-duodenal arteries (from the gastroduodenal artery), the lower pancreas-duodenal artery (from the superior mesenteric artery). Venous outflow: into the pancreatic veins (inflows of the superior mesenteric, splenic and other veins from the portal vein system).
Outflow of lymph: in the pancreas: pancreas-duodenum, pyloric and lumbar lymph nodes.
[14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30]
Age features of the pancreas
The pancreas of a newborn is small. The length is 4-5 cm, the mass is 2-3 g. The gland is located somewhat higher than in the adult. By 3-4 months of life the weight of the gland doubles, by the age of 3 years it reaches 20 g, at 10-12 years its mass is 30 g. Due to the lack of firm fixation to the back wall of the abdominal cavity, the pancreas in the newborn is relatively mobile. By the age of 5-6, the gland takes on a form characteristic of the gland of an adult. Topographic relationships of the pancreas with neighboring organs, characteristic of an adult, are established by the end of the first year of life.