Calf Pancreas - Glass slide #6
We learned that most secretory cells in the pancreas produce zymogens, inactive forms of digestive enzymes. These cells are arranged in roughly spherical structures called acini, hence the name 'acinar cells'. Acini are the functional subunit of the exocrine (zymogen-secreting) pancreas. Try to envision the boundaries of other acini in the exocrine pancreas on your glass slide.
Topic: Exocrine Acini
Acinar cells (yellow outline) of a pancreatic acinus (green outline). Acini are the primary functional subunit of the ducted (blue arrow) exocrine or zymogen-secreting pancreas. In tissue sections acini often appear irregular in shape, though boundaries between adjacent acini are easily identified. Within acinar cells, secretory granules are stored in the apical cytoplasm (red arrows) until needed.
Pancreatic ducts vary significantly. Interlobular ducts have a simple columnar epithelial lining and a significant tunic of circumferential connective tissue. Smaller intralobular ducts have a simple cuboidal lining and a thin collagenous support for their basement membranes.
Topic: Pancreatic ducts
This duct (green arrows) is lined by low cuboidal epithelium. A small amount of collagen surrounds it, suggesting it may be close to merging with an interlobular duct.
Lobules are defined by septa of collagen. These septa may contain nerves and vessels.
Topic: Interlobular septum
Green arrow - peripheral nerve. Red arrow - venule adjacent to a terminal arteriole on its right. Blue arrow, typical collagen stroma of the calf pancreas.
A small islet is visible in this montage. Lighter cells with conspicuous capillaries nearby are usually pancreatic islets. Scan your glass slide for larger or more prominent examples.
Topic: Endocrine islet
Small pancreatic islet
Canine Pancreas, fasted - Glass slide #165
This slide was made from a fasting animal, hence the acinar cells contain an abundance of zymogen granules. The pancreatic duct system begins with small cells inside the acini, called centroacinar cells, which connect to the intercalated ducts. Intercalated ducts are the first and smallest of the ducts, lined with cuboidal epithelium. and Smaller ducts with lower epithelium extend into the lobules as intralobular ducts. Terminal cells of intercalated ducts in acini can often be observed as centroacinar cells.
Topic: Centroacinar cell
Blue arrows indicate a centroacinar cell, the first component of the extensive duct system. Yellow line = approximate boundary of the acinus containing the centroacinar cell.
The intercalated ducts secrete bicarbonate into the pancreatic secretions. They are lined by simple cuboidal epithelium, are branched, and channel zymogens to interlobular ducts.
Topic: Intercalated duct
Blue arrows indicate an intercalated duct at a branch point.
Again, pancreatic islet cells do not stain as intensely as exocrine acinar cells. They are found in clusters where they are arranged along capillaries. Special stains are necessary to distinguish the various types of islet cells.
Topic: Pancreatic islet
A pancreatic islet (blue arrows) surrounded by acinar cells full of red zymogen granules.
Guinea Pig Pancreas - Aldehyde Fuchsin stain; Glass slide #89
Specialized staining with Aldehyde-Fuchsin demonstrates molecules having disulfide bridges. Insulin is the product of islet beta cells and has two disulfide bridges between the A and B chains, thus it stains purple. Orange-staining cells are glucagon containing alpha cells. Note the adipocytes in this pancreas from the Guinea Pig. Try to identify examples of the duct system in this differently-colored slide.
Topic: Pancreatic islet
Arrows indicate the outer margins of this pancreatic islet.