Pancreas histology
Definitions & Key takeaways
The pancreas is an abdominal gland that has both exocrine and endocrine functions. Its exocrine part produces digestive enzymes in the small intestine, while its endocrine part produces hormones such as insulin and glucagon that regulate the body's blood sugar levels. Histologically, three main types of tissue make the pancreas: acinar cells, duct cells, and islet cells. Acinar cells produce enzymes and are secreted into the small intestine to aid digestion.
Duct cells line the pancreatic ducts and secrete a bicarbonate-rich fluid to neutralize stomach acid as it enters the small intestine. Islets of Langerhans produce hormones such as insulin and glucagon. In addition to these three main types of cells, the pancreas also contains supportive stromal cells and blood vessels. The stroma of the pancreas is composed of connective tissue that provides support, blood vessels, and nerve fibers.
The pancreas is a large gland that has both exocrine and endocrine functions.The majority of the pancreas consists of exocrine glands that produce about 1.5 liters of alkaline digestive enzymes daily, which is secreted directly into the duodenum.The pancreas, also contains small endocrine cells found in clusters called islets of Langerhans, which typically stain lighter than the pancreatic tissue around it.The pancreas has a thin collagenous capsule that surrounds the entire pancreas, although only portions of it can be seen in this image.The capsule also extends into the pancreas as septa, forming lobules.This section of the pancreas was prepared with Azan stain, which stains collagen blue-ish purple color in order to highlight structures such as the capsule, septa, as well as the connective tissue that surrounds large blood vessels.Azan stain will also stain the connective tissue surrounding interlobular ducts a similar color as well.But these ducts can be differentiated from the blood vessels by the presence of digestive enzymes instead of red blood cells within their lumen as well as their distinct epithelium that lines the lumen.The epithelium consists of simple columnar cells in this image, but some ducts may also consist of stratified columnar or stratified cuboidal epithelium instead.To the right of the interlobular ducts is an adipocyte.The adipocytes actually increase in number within the pancreas as individuals age, which is a normal finding that’s caused by pancreatic atrophy over time.The main functional tissue of the pancreas is called the parenchyma.If we take a closer look at this slide stained with hematoxylin and eosin, or H&E for short, we can see that the majority of the parenchyma consists of the exocrine portion of the pancreas.
The exocrine secretory cells are arranged in groups that resemble a berry surrounding a central lumen.In latin acini means “berries,” which is why the groups of exocrine cells are called acini.
we can see that the secretory cells are pyramid-shaped and their nuclei are found slightly closer to their bases.This particular slide was stained with H&E, which allows us to see the purple, basophilic rough endoplasmic reticulum seen closer to the base of each secretory cell; and the pink eosinophilic secretory granules at the apices are inactivated enzymes called zymogens.In acute pancreatitis, it’s the exocrine secretory cells that are damaged and end up releasing their enzymes into their immediate surroundings.These strong digestive enzymes cause additional damage to pancreatic tissue and leads to severe inflammation as well.The center of the acini will sometimes contain one or more cells with a paler appearance.These cells are called centroacinar cells and they’re actually extensions of the small ducts that drain the digestive enzymes produced by the acini, called intercalated ducts.The presence of centroacinar cells is a unique feature of the exocrine pancreas and is also an identifying marker that indicates the beginning of the intercalated ducts.These ducts are lined by simple cuboidal epithelium and can be seen in this image as a linear arrangement of cuboidal cells.And in this cross-section of the intercalated duct, you can see the circular duct that is formed by the cuboidal cells.The intercalated ducts then drain into slightly larger intralobular ducts, like the one here.As the ducts progress, they gradually increases in diameter and the connective tissue surrounding these ducts also thickens.The epithelium will also transition from simple cuboidal cells to stratified cuboidal cells.The intralobular ducts then drain into the interlobular ducts, which are located between the lobes, but within the septa.These ducts are lined with epithelium that can be simple columnar, stratified columnar, or stratified cuboidal epithelium; and have a very thick layer of connective tissue surrounding them.
The interlobular ducts eventually join with the large main pancreatic duct, which runs the length of the pancreas and leads to the common bile duct in order to drain into the duodenum.A smaller accessory duct is also often present, which also drains into the duodenum.Let’s move onto the endocrine portion of the pancreas, which forms clusters of paler cells such as the ones seen in this image, called islets of Langerhans.The overall size of the islets can vary, but they can be identified pretty easily by their lighter stain and smaller cells when compared to the surrounding exocrine tissue.When we increase the magnification to 20x, we can see the fenestrated or perforated capillaries within the islet as well.The islets of Langerhans consist of four main types of cells, but they can not be easily distinguished from one another on slides stained with H&E.Beta cells are the most common cell type, which comprises approximately 70% of pancreatic islets and secrete insulin.The islets also consist of alpha cells that secrete glucagon, delta cells that secrete somatostatin, and PP cells that secrete pancreatic polypeptide.This image of an islet was stained with Gomori’s stain, which allows us to differentiate the beta cells that stain bluish-purple, and the alpha cells stained pink; and we can also see just how much of the islet is made of beta cells.In individuals with type 1 diabetes, there’ll be a decreased number of beta cells, as a result of autoimmune destruction of these cells specifically.##SummaryAlright, as a quick recap.The pancreas has both exocrine and endocrine functions.Acini are the berry-shaped groups of exocrine cells that secrete digestive enzymes.The individual secretory cells are pyramid-shaped with basophilic RER and nuclei at their base and eosinophilic granules at the apex.Islets of Langerhans are responsible for the pancreas’ endocrine secretion and are seen with H&E by their paler stain and smaller cells when compared to their surrounding tissue.The islets consist of alpha, beta, delta, and PP cells, with beta cells making up about 70% of the islets.
much of the Earth is made of beta cells and individuals with type 1, diabetes, decrease number of beta cells, as a result of autoimmune destruction, if you sell specifically, all right, as a quick recap, the pancreas an endocrine functions and I are the very shape groups of exocrine cells that secrete digestive enzymes.
The individual secretory cells are pyramid shape, with basic feel like rough endoplasmic, reticulum and nuclei at their base.
And you sent to Philip granules at the Apex islets of langerhans, are responsible for the pancreas is endocrine secretion and are seen with a Cheney by their paler, stain and smaller cells.
When compared to the surrounding tissue. Dallas consist of Alpha Beta Delta and PP cells with beta cells making up about 70% of the eyelets.
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