Compound Glands

00:00 Now, let me describe the pancreas. It's rather a complex gland because it's both exocrine and endocrine. And I think it's worthwhile just having a look at this diagram and just reviewing the duct system in glands. This is both a component of the exocrine glands. And along with the salivary glands which is structured similarly to what you see here, it secretes digestive enzymes.

00:32 It also has an endocrine component, which I explained in a lecture on the endocrine system. But just for a moment, focus on this diagram. Here is a section of a lobe of a salivary gland. Let's say it's the pancreas, the exocrine part of the pancreas.

00:53 And then the lobe, as you know, is divided by connective tissue septa that come in from the capsule of the lobe and divided that lobe into smaller lobules. And within each lobule, you have a series of duct systems that go to individual secretory units or acini. An acinus, if you recall, is a little berry-shaped or a grape-shaped collection or cluster of secretory cells. And each of those little acini secretes into the initial duct system, which is called an intercalated duct, and they in turn feed into a striated duct; striated because of the appearance at the basal aspect of these cells of striations that reflect the very active transport going on there absorbing components. Because in the case of protein secreting salivary glands and salivary acini and in the case here with the pancreas, those intercalated ducts and then those striated ducts, also modify the secretion product. Hence, you see these striations in those striated ducts where there are lots of mitochondria and lots of basal folding to house the transport channels and transport proteins and the energy from the mitochondria to support this very highly active function.

02:20 You don't see these units a lot in the mucous secreting acini because in mucous secreting glands and acini, the secretion product is not modified. The ducts then flow into intralobular ducts, interlobular ducts, interlobar ducts, and then finally, out through the excretory ducts. So make sure you're aware of this duct system, and also the acini. It's common in all glands, in all exocrine compound glands. And the pancreas is one of them.

02:56 And here on the right-hand side, it just summarizes some of the major salivary glands that I've covered in a lecture on the digestive system, the parotid gland at the top, sublingual, and then submandibular. The parotid is essentially serous like the pancreas. The submandibular is mixed. It has both mucous components that's labelled, and then next to it, you can see serous secreting cells.

03:22 And the sublingual is also a salivary gland but it's entirely, or mostly anyway, mucous secreting. And that enables you to distinguish between those three salivary glands. One is purely serous, one is purely mucous, and one is mixed.

03:43 The pancreas is entirely serous, but you can tell it from the parotid gland because the pancreas has the endocrine components in it, the islets, the pancreatic islets.