Mucous Surface and Neck Cells

00:01 I want to now concentrate on the gastric glands. They are the major glands you find throughout the wall or the mucosa of the stomach. It's in the fundus or the body part of the stomach predominantly. And there are a couple of features that we need to describe before we look at the real histology. Again, on the right-hand side at the top, there's a little diagram. It represents the mucosa. It represents, first of all the top part, there's a little pit, a little hole, a beginning, an opening, if you like, and that opening goes down into the gastric glands. And the gastric gland can, or at least the pit, can be the conveyance area, the portion of the glands that can deliver those secretory products from one, two, or at least three of these gastric glands so they combine, they unite at the top in these pits to release their products.

01:07 And again, those glands are supported by the muscularis mucosa. And you'll see they extend all the way down to the level of the muscularis mucosa. So appreciate that generalized diagram first, then look across to the left-hand picture.

01:29 Here, a gastric gland is illustrated, and there are three major types of cells, and we'll go through each of these cells in this lecture. The surface cells are called surface mucous cells.

01:47 They are at the surface and the initial entry of the pit, the gastric pit.

01:53 And then you have mucous neck cells, the next ones down. And they are at the isthmus or they're at the level where the gastric glands are going to branch.

02:06 As I said earlier, a number of these gastric glands open into a common gastric pit.

02:10 That common gastric pit is lined by mucous cells. And then you have two other cell types. In the middle area of the gastric pit, there are parietal cells, and I'll describe those in a moment. Below that, there are these blue-stained chief cells.

02:35 The parietal cell, the chief cell, and the mucous cells at the neck and the surface are the three major types of cells in gastric pits. But there are also enteroendocrine cells, cells that secrete hormonal products. And we don't often see this in routine histological sections. You have to use special stains. I'm not going to mention this in great detail in this lecture, but understand they exist and they have very important functions, for instance, secreting the hormone gastrin that has an effect on the stomach. And the physiologist will explain to you all about the physiology of all these hormonal products when you study physiology. There is also stem cells that I will talk to you about in a moment.

03:31 Move across to the right hand bottom part of the slide and you'll see a histological section now taken through the gastric gland. Again, labelling the various components; the pit, the neck, and the body.

03:47 And you can see a dark-stained collection of cells right next to the muscularis mucosa that represent chief cells. And there is also clusters of parietal cells you'll see towards the middle region. In a moment, I'm going to tell you how you can identify each of these different cell types. But this is just to orientate you as to the structure of these gastric glands before we move on. On the left-hand side, we have our picture and our section has been labelled. But now on the right-hand side, we have a real section taken through the mucosa of the stomach.

04:37 And I want you to look at that carefully. See if you can actually identify the mucous surface cells and the parietal cells, and perhaps, the chief cells.

04:53 You know by now they are located at various parts, generally, in the mucosa. There, the mucous neck cells, clear staining. The mucous gets lost during the processing, so the cells would appear very clear. The parietal cells are these red-stained areas towards the middle of the gastric gland, and then the chief cells, are at the base. Although, when you look at these chief cells, you'll also find cluttered among them some parietal cells as well. And then underneath, you have the very thin layer of the muscularis mucosa also shown.

05:43 Let's concentrate on each of these cell types now in a little bit more detail and talk about their function. On the left-hand side, again, is our nice helpful diagram. The top layer of blue-stained or blue-coloured cells represents the mucous surface cells, mucous surface. Note the spelling of the word mucous. That refers to the adjective, the descriptive term of the cells.

06:16 Mucus refers to the product, the mucous product of the cell. So make sure you're aware of that difference in spelling. If you look now at the middle section, you can see the pale-staining cells that make up the surface of the gastric glands. And on the far right-hand side, you can make out the cells that make up the neck of the glands. Here are the mucous surface cells. Note the spelling, mucous the adjective describing the surface cells and mucus the product. And again, on the right-hand side, you can see the neck cells. Now, you should be able to observe that the mucous neck cells are much smaller than the surface cells. They have more prominent nuclei, but they are smaller. And the mucous neck cells actually secrete a soluble type of mucus. The mucous surface cells secrete an insoluble type of mucus.

07:30 And that's very important. That insoluble mucus forms a layer on the surface of those mucous cells, separating the epithelium and the gastric glands from the harsh environment in the lumen where the chyme is moving a battle at time due to the mixing activity of this stomach.

07:54 So these surface cells need to be protected against that mechanical abrasion. So that's the job of this very insoluble mucus. It's a very thick viscous type mucus. It's protective. But there's another job that this mucus does, this insoluble mucous does. It binds bicarbonate. It doesn't allow bicarbonate that's produced, into the lumen to mix into the lumen with the chyme.

08:29 It concentrates that bicarbonate in that insoluble mucous, and that's one of its major jobs. And concentrating that bicarbonate inside that insoluble mucus is very important to stop the acid attack on the underlying epithelium.

08:47 It's again another protective role. And the secretion of this insoluble mucous and the concentration of bicarbonate in that insoluble mucous and the secretion of the clearly watery mucus from the mucous neck cells is controlled by the vagal nerve. The vagal stimulation from the vagus nerve comes down and produces the secretion of those mucus components. And it only happens when the stomach fills with food and it's breaking down and mixing food. It doesn't happen at all when the stomach is in a resting phase.