Editing Pancreas (section)

===Microanatomy===
[[File:Langerhanssche Insel.jpg|thumb|This image shows a [[pancreatic islet]] when pancreatic tissue is stained and viewed under a microscope. Parts of the digestive ("exocrine") pancreas can be seen around the islet, more darkly. These contain hazy dark purple granules of inactive digestive enzymes ([[zymogen]]s).]]
[[File:Human pancreatic islet.jpg|thumb|A pancreatic islet that uses [[immunohistochemistry|fluorescent antibodies]] to show the location of different cell types in the pancreatic islet. Antibodies against glucagon, secreted by alpha cells, show their peripheral position. Antibodies against insulin, secreted by beta cells, show the more widespread and central position that these cells tend to have.{{sfn|Wheater's Histology|2013|pp=332-333}} ]]
The pancreas contains tissue with an [[endocrine]] and [[exocrine]] role, and this division is also visible when the pancreas is viewed under a microscope.{{sfn|Wheater's Histology|2013|pp=287-291}}

The majority of pancreatic [[Parenchyma|tissue]] has a digestive role. The cells with this role form clusters ([[acini]]) around small [[duct (anatomy)|ducts]], and are arranged in lobes that have thin [[fibrous tissue|fibrous]] walls. The cells of each acinus secrete inactive digestive enzymes called [[zymogen]]s into the small ''intercalated'' ducts which they surround. In each acinus, the cells are pyramid-shaped and situated around the intercalated ducts, with the [[Cell nucleus|nuclei]] resting on the [[basement membrane]], a large [[endoplasmic reticulum]], and a number of zymogen granules visible within the [[cytoplasm]]. The intercalated ducts drain into larger ''intralobular'' ducts within the lobule, and finally ''interlobular'' ducts. The ducts are lined by a single layer of [[columnar epithelium|column-shaped cells]]. There is more than one layer of cells as the diameter of the ducts increases.{{sfn|Wheater's Histology|2013|pp=287-291}}

The tissues with an [[endocrine]] role within the pancreas exist as clusters of cells called [[pancreatic islets]] (also called islets of [[Paul Langerhans|Langerhans]]) that are distributed throughout the pancreas.{{sfn|Wheater's Histology|2013|pp=332-333}} Pancreatic islets contain [[alpha cell]]s, [[beta cell]]s, and [[delta cell]]s, each of which releases a different hormone. These cells have characteristic positions, with alpha cells (secreting [[glucagon]]) tending to be situated around the periphery of the islet, and beta cells (secreting [[insulin]]) more numerous and found throughout the islet.{{sfn|Wheater's Histology|2013|pp=332-333}} [[Enterochromaffin cell]]s are also scattered throughout the islets.{{sfn|Wheater's Histology|2013|pp=332-333}} Islets are composed of up to 3,000 secretory cells, and contain several small arterioles to receive blood, and venules that allow the hormones secreted by the cells to enter the [[systemic circulation]].{{sfn|Wheater's Histology|2013|pp=332-333}}