Mucous and Serous Glands

00:01 I mentioned earlier that there are some cells such as the goblet cell that secretes a mucous type product. But there are also other cells that secrete a serous type product and I will explain what those two types of products really are in a moment. In this slide, you can see two images, two histological sections taken through two different exocrine glands. One is dominated by mucous secreting units.

00:38 The other is dominated by serous secretory units. And you see here, they stain very differently.

00:45 In the case of the mucous secreting unit or mucous secreting cells, the blue tinge or the light staining is due to the component of the secretory product. Mucous secreting cells or mucous secreting units, we call them asini as well which I will explain later on.

01:09 They secrete proteins that are glycosylated with an anionic oligosaccharides. And because of that, these proteins, the secretory products are water soluble. So depending on the fix that you use, often, the secretory products are lost from the cell. Here in some way, there have been a little bit retained. On the right-hand side, you see serous secreting cells. These are proteins and if the tissue has been preserved very well, you can see little tiny granules containing these protein secretory products stored in small vesicles at the apex of the cells. Often you will see the rest of the cell, the rest of the cytoplasm basophilic and this reflects the enormous protein factory inside the cell that is making the secretory product. Go back to the mucous secreting unit. The cells there have nuclei that are squashed against the base of the cell so they appear flattened.

02:30 The serous secreting cells have nice rounded nuclei and often that is a good indication or a good way to identify the difference between mucous secreting cells and serous secreting cells.

02:45 Sometimes a gland can have both secretory units. Here you see a serous secreting unit, very pink staining, here you see a mucous secreting unit. And here is an example of what I've described before where the secretory product is water soluble and lost during the normal tissue processing where you use to examine sections of tissue stained with hematoxylin and eosin. Down below, if you look very carefully, you can see three profiles of duct system.

03:25 These ducts, remember, carry the secretion product from the secretory cells to an exterior location. And these locations can be often some distance from where the gland is housed within the body. And we will see an example of that when we look at the pancreas.

03:47 It has a long duct that opens into the duodenum some distance away.