4.4.0 DIGESTIVE TRACT: PANCREAS: INTRODUCTION
The pancreas consists of an exocrine gland with endocrine islets (of Langerhans):
1. The exocrine gland is constructed as lobes, and each lobe contains ducts and acini. Each acinus has an individual intra-acinar duct which drains into progressively larger ducts.The acinar cells produce secretory zymogen granules containing digestive enzymes such as carboxypeptidase, trypsin (chymotrypsin), nucleases, amylases and lipases, elastases released as inactive forms, which become activated subsequently in the lumen of the digestive tract. The pancreas secretion is affected by duodenal hormones secretin and cholecystokinin. Secretin stimulates the bicarbonate production in the centroacinar cells and in the cells of the intercalated ducts. Cholecystokinin stimulates the acinar cells. The blood levels of amylase and lipase are used as markers for the exocrine pancreas condition. The pancreatic secretion is alakline due to the bicarbonate ions produced by the ductal epithelial cells. The main pancreatic ducts end and empty in the duodenal lumen at the ampulla of Vater with a sphincter.
See: POJA-L4200; POJA-L0251; POJA-L2838+3542
2. The endocrine Langerhans islets consist of clusters of endocrine cells of three types, α-, β- and δ-cells. The α-cells produce glucagon that elevates the blood glucose level via liver glycogen. The β-cells produce insulin that lowers the blood glucose level in favor of formation of glycogen in liver and muscles, while the δ-cells generate somatostatin that modulates the release of insulin and glucagon. Usually the islets of Langerhans consist of about 20% α-cells, 60-80% β-cells and 8% δ-cells. A fourth cell type is called PP-cells and produces pancreas polypeptide acting as gastrin antagonist lowering the HCl production in the stomach. The insulin granule possess a clear zone surrounding the dense granule. β-granule has crystalline inclusions. The islets have numerous fenestrated capillaries.
See: POJA-L2845+2846; POJA-La0250+2853+2854.
3. Pathology.
Insulinoma: See: 4.4.1 POJA-L2851+2852.
Pancreas adenocarcinoma: See: 4.4.1 POJA-L3320+3321+3322.
1. The exocrine gland is constructed as lobes, and each lobe contains ducts and acini. Each acinus has an individual intra-acinar duct which drains into progressively larger ducts.The acinar cells produce secretory zymogen granules containing digestive enzymes such as carboxypeptidase, trypsin (chymotrypsin), nucleases, amylases and lipases, elastases released as inactive forms, which become activated subsequently in the lumen of the digestive tract. The pancreas secretion is affected by duodenal hormones secretin and cholecystokinin. Secretin stimulates the bicarbonate production in the centroacinar cells and in the cells of the intercalated ducts. Cholecystokinin stimulates the acinar cells. The blood levels of amylase and lipase are used as markers for the exocrine pancreas condition. The pancreatic secretion is alakline due to the bicarbonate ions produced by the ductal epithelial cells. The main pancreatic ducts end and empty in the duodenal lumen at the ampulla of Vater with a sphincter.
See: POJA-L4200; POJA-L0251; POJA-L2838+3542
2. The endocrine Langerhans islets consist of clusters of endocrine cells of three types, α-, β- and δ-cells. The α-cells produce glucagon that elevates the blood glucose level via liver glycogen. The β-cells produce insulin that lowers the blood glucose level in favor of formation of glycogen in liver and muscles, while the δ-cells generate somatostatin that modulates the release of insulin and glucagon. Usually the islets of Langerhans consist of about 20% α-cells, 60-80% β-cells and 8% δ-cells. A fourth cell type is called PP-cells and produces pancreas polypeptide acting as gastrin antagonist lowering the HCl production in the stomach. The insulin granule possess a clear zone surrounding the dense granule. β-granule has crystalline inclusions. The islets have numerous fenestrated capillaries.
See: POJA-L2845+2846; POJA-La0250+2853+2854.
3. Pathology.
Insulinoma: See: 4.4.1 POJA-L2851+2852.
Pancreas adenocarcinoma: See: 4.4.1 POJA-L3320+3321+3322.
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All rights reserves worldwide for the POJA collection are hold by L.G. Poels and P.H.K. Jap and Radboud University Medical Center (Radboud UMC Nijmegen). No one may modify, copy, distribute, transmit, display, or publish any materials contained in the POJA collection without prior written permission of the authors Poels and Jap or the UMC St Radboud. Any commercial use of the POJA collection is forbidden. POJA images are partly deposited in the Health Education Assets Library (HEAL database) as well as in the MedEdPortal/AAMC database).
All rights reserves worldwide for the POJA collection are hold by L.G. Poels and P.H.K. Jap and Radboud University Medical Center (Radboud UMC Nijmegen). No one may modify, copy, distribute, transmit, display, or publish any materials contained in the POJA collection without prior written permission of the authors Poels and Jap or the UMC St Radboud. Any commercial use of the POJA collection is forbidden. POJA images are partly deposited in the Health Education Assets Library (HEAL database) as well as in the MedEdPortal/AAMC database).