Glandular Epithelial Tissue - Online Tutor, Practice Problems & Exam Prep

Exocrine vs. Endocrine Glands

In this video, we're going to begin our lesson on glandular epithelial tissue. Recall from our previous lesson videos that glandular epithelial tissue, as its name implies, is going to be epithelial tissue that forms glands. Recall from our previous lesson videos that a gland can be defined as a cellular structure that is specialized for secretion or releasing products into the environment. Or in other words, we can say that a gland is really just a single cell or a group of cells that once again is going to secrete a product. For example, that secreted product could be something such as sweat, bile, or hormones. Now glands themselves can actually be broadly categorized into 2 major groups. The first major group is exocrine glands, and the second major group is endocrine glands. Let's take a look at our image below to distinguish these two. Notice on the far left, we have exocrine glands and on the far right, we have endocrine glands. Notice that for exocrine glands, we have the 'EX' underlined. This can be used as a memory tool to remind you that exocrine gland secretions are going to exit into a body surface or into a body cavity. You can think the 'EX' in exocrine is for the 'EX' in exit, for the secretions exiting onto a body surface or into a body cavity. On the other hand, for endocrine glands, notice that we have the 'EN' underlined. Again, this is a memory tool to remind you that the secretions of endocrine glands are going to enter into the blood or into the bloodstream. You can think the 'EN' in endocrine is for the 'EN' in enter, to remind you that the secretions again enter into the blood. In terms of exocrine glands, they can either be unicellular glands, meaning that they're made of just one single cell, or they can be multicellular glands. As we move forward in our course, we'll talk more about some of those unicellular examples. Note here that the multicellular glands that are exocrine, they use structures known as ducts to release their products. The endocrine glands, on the other hand, tend to be multicellular, and they actually do not use ducts to release their products. Below what we have are some example secretions for exocrine glands, and they include things such as mucus, sweat, oil, and milk. Whereas for endocrine glands, the secretions tend to be hormones or chemical messengers. These hormones can affect distant organs. The reason for that is because the secretions are going to enter into the blood and the blood is pretty much a highway throughout the entire body. There are blood vessels that go into almost all regions of our body. Once the secretion enters into the blood, it can travel through the blood to a distant organ and affect that distant organ. If we take a look at the images below, what you'll notice is on the left side for exocrine glands, we can see that the epithelial tissue is folding in as you see here, and that is creating the duct that you can see highlighted right there. These exocrine glands are going to release their products into the ducts and when they release their products into the ducts those products can exit onto either a body surface or into a body cavity. These cells here that are forming the exocrine glands are considered exocrine glandular epithelial tissue. Over here on the right, the endocrine gland is actually right here in this region. Notice that the endocrine gland is going to release its secretions into the blood. So the secretions enter into the blood or the bloodstream. Once again, once the secretion is entering into the blood, it can travel through the blood, which is again pretty much like a highway through the body, and it can travel to other regions and affect distant organs. One thing that you'll notice here is that the endocrine glandular epithelial tissue here is not adjacent to open space, which we said in previous videos is pretty much a key defining feature of epithelial tissue. Endocrine glands are an exception to that key feature of epithelial tissue. Notice that the endocrine gland here is not immediately adjacent to open space as you see up above. One thing that is noteworthy though, is that when this epithelial tissue of the endocrine gland is forming, it actually initially starts with a duct that is opening up to the open space. But as this tissue develops, it actually loses the duct and, it is going to appear as if it is not epithelial tissue, but it actually is epithelial tissue and it has those derivations there. This here concludes our brief introduction to glandular epithelial tissue. As we move forward in our course, we're going to focus our attention mostly on exocrine glands. The reason for that is because later in our course, we have a chapter on the endocrine system, which includes endocrine glands. We'll talk a lot more about those endocrine glands later in our course. For now, we're going to move forward focusing on exocrine glands. That being said, I'll see you all in our next video.

Glandular Epithelial Tissue Example 1

So here we have an example problem that says the gland at the right releases a product. Use evidence from the image to determine if the structure is an endocrine or an exocrine gland. And so, option A says endocrine, and option B says exocrine. And so taking a look at this image on the right of the gland, notice that the glandular epithelial tissue is folding in in this format that you see here. The connecting cells that are folding in have not been lost; they are retained through the development of this gland. And so, they are actually forming these ducts that you can see highlighted in these regions. And so, recall that multicellular exocrine glands use ducts like this, but endocrine glands do not use ducts.

Also, what you'll notice is that the glandular epithelial tissue is secreting the product here, these little blue circles, into the ducts. And then, the secreted product can then exit onto either a body surface or into a body cavity. And so, recall that the secreted product exiting onto a body surface or into a body cavity is going to be a sign of exocrine glands. You can think the EX in exocrine is for the EX and the secretions exiting.

And so, recall that endocrine glands, on the other hand, their secretions are going to enter into the blood. We don't really see these secretions entering into anything that seems like it's entering into the blood. It looks like it's being, exiting onto a body surface or a body cavity. And so everything that we're seeing here is aligning with answer option B, exocrine glands. So we can go ahead and indicate B here is the correct answer to this example problem. And that concludes this example, so I'll see you all in our next video.

A mother breastfeeding her infant is utilizing what type of gland for that process? 

• A. Paracrine.
• B. Endocrine.
• C. Exocrine.
• D. Stratified.

Unicellular Exocrine Glands - Goblet Cells

In this video, we're going to begin our lesson on unicellular exocrine glands, more specifically, goblet cells. And so, of course, unicellular exocrine glands are going to be single-celled exocrine glands since recall that the root 'uni' means 1. And so the most common unicellular exocrine gland is going to be the goblet cell. And so the goblet cell is named because its shape actually resembles that of a goblet or a wine glass, if you will. And we'll be able to see that down below in our image. Now there actually is another notable unicellular exocrine gland and that is the mucus cell. But really the mucus cell is effectively the same as the goblet cell. The biggest difference is that the mucus cell does not take on the shape of a goblet. Whereas, of course, the goblet cells do take on the shape of a goblet. Now these goblet cells are going to be found sprinkled in or dispersed in the epithelial tissue that lines the respiratory and intestinal tracts. And, in fact, these goblet cells are going to be found in tissue that is usually shaped with columnar cells, long, tall, and narrow-shaped cells.

Now these goblet cells are going to be secreting vesicles that are filled with a product called mucin, which is not to be confused with mucus. Mucin is a glycoprotein that can ultimately form mucus, and mucus is going to be important for lubricating and protecting the epithelial tissue. Now, this mucin glycoprotein is going to be secreted by these goblet cells via exocytosis. And so let's take a look at our example image down below where we can label the missing words on the diagram of the goblet cell. And so, once again, these goblet cells are going to be found sprinkled in or dispersed in the epithelial tissue that lines the respiratory tract and the intestinal tract. And so notice that up above we have a micrograph from the respiratory tract and down below we have a micrograph from the intestinal tract.

And what you'll notice is that both of these have some goblet cells sprinkled in the epithelial tissue lining those tracts. And so, notice that these goblet cells that are being indicated here, they actually take on the shape of a goblet or a wine glass, if you will. And so, if we do the outline here, you can see that a little bit more clearly. There's actually another goblet cell over here that we can trace. And then down below in the intestinal tracts, again, there are also these goblet cells and again you can see their goblet shape or their wine glass shape right there. And so over here we actually have the goblet shape here. Again, it resembles that of a wine glass where it's wider at the top here and narrower toward the bottom. And then over here, what we have is yet another figure showing you the goblet cell here, embedded in that epithelial tissue lining of the respiratory and intestinal tract. And so notice that we're actually labeling the nucleus here of the goblet cell.

You can see all of these other organelles of the goblet cell. And we're also labeling these secretory vesicles that are again filled with mucin, the glycoprotein that ends up forming mucus. But again, mucin is not to be confused with mucus. And so we know that these secretory vesicles are going to be secreted by the goblet cell via exocytosis, and then that mucin can ultimately form mucus. And so you can see the layer of mucus here in green, above the epithelial tissue. And again, this mucus is going to be important for lubricating and protecting the epithelial tissue. Now, we're also labeling the microvilli of the goblet cell, which can be important for absorption.

This here concludes our brief lesson on unicellular exocrine glands, more specifically, the goblet cells, and we'll be able to get some practice applying these concepts and learn more as we move forward. So I'll see you all in our next video. Oh, and I almost forgot, my goblet with a green drink in it. Cheers. Delicious.

Which of the following is a primary function of goblet cells? 

• A. Lubricating and protecting the epithelium. 
• B. Secreting mucus. 
• C. Producing hormones. 
• D. Absorbing wastes.

If you had many more goblet cells than you're supposed to, which symptom are you most likely to experience?

• A. A dry throat. 
• B. Low hormone levels. 
• C. Difficulty breathing. 
• D. High blood pressure.

Modes of Secretion: Merocrine, Holocrine & Apocrine

In this video, we're going to begin our lesson on multicellular exocrine glands, more specifically focusing on their mode of secretion. And so, of course, multicellular exocrine glands are going to be composed of multiple cells. And because they are composed of multiple cells, they are going to be structurally more complex than unicellular glands. Now these multicellular exocrine glands can actually be grouped into 3 different types simply based on their modes of secretion or exactly how they go about secreting their product or releasing their products. And so these three different modes of secretion are, number 1, merocrine secretion, also known as eccrine secretion. Number 2 is holocrine secretion. And number 3 is apocrine secretion. And so, merocrine secretion is merely going to be using exocytosis in order to secrete products. And this is actually the most common form of secretion. It is the most common mode of secretion. And so, exocytosis is a pretty standard process for secreting products. And so, hopefully, bolding the MER here in merely can be used as a memory tool for you to remind you that Merocrine Secretion merely uses exocytosis to secrete products. Now moving on, holocrine secretion is going to be when the whole cell is going to rupture and die upon secreting the product. In fact, the root hollow, which you can see here in holocrine, is a root that means whole. And so hopefully, this can be used as a memory tool to remind you that holocrine secretion is when the whole cell is going to rupture and die in order to secrete the product. Now, because cells are actually dying in this process of secretion, this means that the gland is going to need to replace those dying cells in order to continuously secrete. Now, moving on, the 3rd and final mode of secretion is apocrine secretion. And in apocrine secretion, it is the apical portion of the cell that is going to shed off in order to secrete the product. But unlike holocrine secretion where the cell is going to die, in apocrine secretion, the cell does not die when that apical portion of the cell sheds off. And so let's take a look at our image down below where we can get a better understanding of these modes of secretion used by these multicellular exocrine glands. And so, notice in our image on the far left, we have merocrine secretion. In the middle here, we have holocrine secretion. And on the far right, we have apocrine secretion. And so recall that merocrine secretion, also known as eccrine secretion, is when cells merely secrete products via exocytosis. And so notice that the glandular epithelial tissue here is, folding in and it is forming this duct that you see right here. And if we zoom into the cells right over here in this region, what you'll notice is that the cells are secreting their products here via exocytosis. And so you can see that the secretory vesicles are being labeled in blue and, when they release their products, the cell secretion products are in the duct. And again, these cell products that are secreted into the duct can then exit onto either the body surface or an internal body cavity. Now, an example of a gland that utilizes merocrine secretion is going to be the salivary glands, which produces saliva. Now, moving on, we have the holocrine mode of secretion. And again, the root hollow means whole. And so this reminds us that the whole cell is actually going to rupture and die in this mode of secretion. And so, notice here that we have, again, our glandular epithelial tissue here and the cells are actually going to break off into the duct. And eventually these cells are going to rupture and die. And when these, if we zoom in right here, what you'll notice is that when these cells rupture and die, they are actually secreting their products. And so, an example of a gland that utilizes holocrine secretion is going to be the sebaceous glands, which secrete oil. And then last but not least, what we have is apocrine secretion over here on the far right, and apocrine secretion is going to be again when the apical portion of the cell is going to shed off. And so what you'll notice here is we have the glandular epithelial tissue once again. And if we zoom in, notice that the entire apical portion of the cell is shedding off. However, the cells are not going to die unlike holocrine secretion. And so, a classic example of a gland that utilizes apocrine secretion is going to be the mammary glands. And so this here concludes our brief lesson on multicellular exocrine glands and their modes of secretion, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.

Which type of multicellular gland needs to be completely regenerated each time it secretes product? 

• A. Merocrine.
• B. Apocrine.
• C. Holocrine.
• D. None of these.

Which type of gland doesn't need to be repaired at all after secretion?  

• A. Merocrine.
• B. Apocrine.
• C. Holocrine.
• D. None of these.

Which type of secretion is most consistent with how goblet cells secrete? 

• A. Merocrine.
• B. Apocrine.
• C. Holocrine.
• D. None of these.