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Exocrine

Endocrine: islets

The human pancreas, from organ to cell

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Region

Duct tree: a large interlobular duct in the septa, interlobular ducts to each lobule, intralobular ducts inside, terminal (intercalated) ducts ending in acini
Acini, in grape-like clusters at the ends of the terminal ducts (drawn sparser than real, so the ducts show)
Lobules cut across, purple as in H&E, with pale pink septa of connective tissue between them: the ring round the opening
Islets: pale islands among the acini, sizes about the mean of 110 µm, at the region’s density
Interlobular ducts, with an artery (red) and vein (blue), in the septa

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Simulated: built from published descriptions and measurements

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Stain

Cell types colours each kind of cell like a multiplex immunofluorescence panel: acinar orange, duct teal, beta green, alpha magenta, delta cyan, PP amber, capillaries red, stellate cells yellow, collagen lavender, nuclei blue.

Acinar cellsWedges converging on the lumen like orange segments. As in H&E: the base stains purple with hematoxylin (rough ER), the apex pink-red with eosin (zymogen granules); round, dark basal nuclei. Cut cells show their stained interior.
Ducts and centroacinar cellsPale-staining cuboidal cells in intralobular ducts, low flat cells in intercalated ducts, pale centroacinar cells inside each acinus; round nuclei.
CapillariesA looping network between acini; the islet has its own dense bed.
Red blood cells
StromaCollagen aligned along the ducts (CODA), loose fibres, spindle-shaped stellate cells.
IsletIn H&E, a pale island among the darker acini, its cells alike with round nuclei. Switch the stain to Cell types to see beta (green), alpha (magenta), delta (cyan) and PP (amber) cells.

Nucleus, basal
Rough ER round the nucleus: makes the enzymes
Golgi above the nucleus: packages them
Zymogen granules, about 1 µm, at the apex
Enzymes released into the lumen and down the duct (with Motion on)
Mitochondria

Insulin granules, about 350 nm: dark cores of insulin with zinc, in clear halos
Glucose entering from the blood (with Motion on)
Insulin released into the capillary (with Motion on)
Nucleus
Golgi; rough ER in blue
Mitochondria
Primary cilium

Glucagon granules, about 200 nm: dense, with little or a grey halo
Glucagon released into the capillary (with Motion on)
Nucleus
Golgi; rough ER in blue
Mitochondria
Its capillary

Somatostatin granules, about 250 nm, homogeneous
Processes reaching neighbouring beta and alpha cells (1–18 µm in human islets)
Somatostatin released beside its neighbours (with Motion on)
Nucleus
Golgi; rough ER in blue
Mitochondria

Nucleus, central
Mitochondria, many: secretion needs energy
Microvilli on the apical surface, facing the lumen
Primary cilium, one per cell, into the lumen
Tight junctions: a belt sealing the apical edge
CFTR, apical anion channel
SLC26A6, apical Cl⁻/HCO₃⁻ exchanger
Basement membrane, beneath the cell
Bicarbonate leaving into the lumen and carried along it (with Motion on)

How the tissue is built

Acinar cells reach out until they meet a neighbouring acinus, a vessel, a duct or the islet, so acini deform against one another; they fill 52% of each tested block. Sizes of acinar, centroacinar, duct and beta cells, acini, granules, capillaries and stellate cells are typical values not yet sourced; the duct tree and centroacinar cells are described in rat (Endo 2002). The core is cut from the 300 µm block built and tested for its region; in the uncinate process its islet is PP-rich.

Sources

HRA 3D reference organs (HuBMAP), from the Visible Human Project. CC BY 4.0.
Kiemen AL, et al. CODA. Nat Methods 2022. doi:10.1038/s41592-022-01650-9
Endo H, et al. Pancreatic ductular system. Histol Histopathol 2002. doi:10.14670/HH-17.107
Beer RL, et al. Centroacinar cells. Dev Biol 2016. doi:10.1016/j.ydbio.2016.02.027
Messenger SW, et al. Granule exocytosis in acinar cells. Cell Calcium 2014. doi:10.1016/j.ceca.2014.03.003
Palade G. Intracellular aspects of the process of protein synthesis. Science 1975. doi:10.1126/science.1096303
Hahn M, et al. 2021; Wang X, et al. 2013; Cabrera O, et al. 2006; Brissova M, et al. 2005: islets.
Berclaz C, et al. Insulin–zinc crystals in beta cell granules. Diabetologia 2016. doi:10.1007/s00125-015-3819-x
Ishiguro H, et al. Bicarbonate secretion by pancreatic duct epithelium. Nagoya J Med Sci 2012. PMC4831246
Hegyi P, Rakonczay Z. Pancreatic ducts in acute pancreatitis. Pancreatology 2015. doi:10.1016/j.pan.2015.03.010
Steward MC, Ishiguro H. Pancreatic duct cell function. Curr Opin Gastroenterol 2009. doi:10.1097/MOG.0b013e32832e06ce
diIorio P, et al. Cilia in the pancreas. Birth Defects Res C 2014. doi:10.1002/bdrc.21064
Narration written for this viewer after: StatPearls, Anatomy, Abdomen and Pelvis, Pancreas (NCBI Bookshelf NBK532912) and the StatPearls chapter on the endocrine pancreas (NBK459261), CC BY 4.0; Columbia University histology laboratory notes on the exocrine and endocrine pancreas; University of Basel histology collection, exocrine pancreas; Human Protein Atlas, normal pancreas.