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

Glandular epithelial tissue forms glands specialized for secretion, categorized into exocrine and endocrine glands. Exocrine glands release products via ducts onto body surfaces or cavities, while endocrine glands secrete hormones directly into the bloodstream. Unicellular exocrine glands, like goblet cells, secrete mucin for lubrication, whereas multicellular exocrine glands utilize merocrine, holocrine, or apocrine secretion modes. Merocrine secretion uses exocytosis, holocrine involves cell rupture, and apocrine sheds the apical portion without cell death, exemplified by salivary, sebaceous, and mammary glands, respectively.

Exocrine vs. Endocrine Glands

In this video, we're going to begin our lesson on glandular epithelial tissue. And so recall from our previous lesson videos that glandular epithelial tissue, as its name implies, is going to be epithelial tissue that forms glands. And so 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. And so, for example, that secreted product could be something such as sweat or bile or hormones, for example.

Now, glands themselves can actually be broadly categorized into 2 major groups. The first major group are exocrine glands, and the second major group are endocrine glands. And so let's take a look at our image down below to distinguish these 2. And so notice on the far left, we have exocrine glands, and on the far right, we have endocrine glands. Now notice that for exocrine glands, we have the EX underline.

And so that 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. And so you can think the EX in exocrine is for the EX and exit for the secretions exiting onto a body surface or into a body cavity. Now on the other hand for endocrine gland, notice that we have the 'EN' underline. And, 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. And so you can think the 'EN' in endocrine is for the 'EN' in enter, to remind you that the secretions again enter into the blood.

Now, 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. And when we move forward in our course, we'll talk more about some of those unicellular examples. But what you should note here is that the multicellular glands that are exocrine, they use structures known as ducts in order to release their products. And so the endocrine glands on the other hand, they tend to be multicellular, and they actually do not use ducts in order to release their products. Now, down below what we have are some example secretions for exocrine glands, and they include things such as mucus, for example, sweat, oil, and milk.

Whereas for endocrine glands, the secretions tend to be hormones or chemical messengers. And these hormones can affect distant organs. And so the reason for that is because, again, 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 pretty much go into almost all regions of our body. And so once the secretion enters into the blood, it can travel through the blood to a distant organ and affect that distant organ.

And so if we take a look at the images down below, what you'll notice is on the left side for exocrine gland, 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. And so, what you'll notice is that 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 exit into a body cavity, for example. And so, what you'll notice is that these exocrine glands, these cells here that are forming the exocrine glands are considered exocrine glandular epithelial tissue. Now, over here on the right, what you'll notice is that the endocrine gland is actually right here in this region. And notice that the endocrine gland is going to release its secretions into the blood, so the secretions enter into the blood or the bloodstream.

And 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. Now one thing that you'll note 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. And so really, endocrine glands are an exception to that key feature of epithelial tissue. Because notice that the endocrine gland here is not immediately adjacent to open space as you see up above. And so, 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. And so this here concludes our brief introduction to glandular epithelial tissue. And as we move forward in our course, we're going to focus our attention mostly on exocrine glands. And the reason for that is because later in our course, we have a chapter on the endocrine system, which includes endocrine glands. And so we'll talk a lot more about those endocrine glands later in our course.

And so, for now, we're gonna move forward focusing in on exocrine gland. And so 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 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. 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.

They are actually forming these ducts that you can see highlighted in these regions. Recall that multicellular exocrine glands use ducts like these, but endocrine glands do not use ducts. Additionally, the glandular epithelial tissue is secreting the product, these little blue circles, into the ducts. Then, the secreted product can exit onto either a body surface or into a body cavity. Recall that the secreted product exiting onto a body surface or into a body cavity is a sign of exocrine glands.

Think of the "EX" in exocrine as for the secretions exiting. Recall that endocrine glands, on the other hand, have their secretions entering the blood, and we don't really see these secretions entering into anything that seems like it's entering the blood. It looks like it's being exiting onto a body surface or a body cavity. Thus, everything that we're seeing here is aligning with answer option B, exocrine gland. So, we can go ahead and indicate that option 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" is a root that 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. And so 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. Multicellular exocrine glands are composed of multiple cells and, because of this, they are structurally more complex than unicellular glands. These multicellular exocrine glands can be grouped into three different types simply based on their modes of secretion or exactly how they go about secreting their product or releasing their product. 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. Merocrine secretion is going to use exocytosis to secrete products. This is actually the most common form of secretion and is a standard process. Bolding the "MER" here in "merely" can be used as a memory tool to remind you that merocrine secretion merely uses exocytosis to secrete products. Holocrine secretion involves the whole cell rupturing and dying upon secreting the product. The root "holo," which can be seen in "holocrine," means whole, helping to remember that in this process, the whole cell is affected. As cells die during this process, the gland needs to replace those dying cells to maintain secretion capabilities.

The third and final mode of secretion is apocrine secretion, where the apical portion of the cell sheds off to secrete the product, without the cell dying. Below, we'll explore these modes of secretion as used by multicellular exocrine glands more visually. On the far left of our image, you see merocrine secretion. The middle shows holocrine secretion, and on the far right, apocrine secretion. Merocrine secretion, also known as eccrine secretion, involves cells secreting products via exocytosis wherein the glandular epithelial tissue folds in, forming a duct visible here.

In this region, cells secrete their products via exocytosis as indicated by the secretory vesicles labeled in blue. When these products are released, they enter the duct and can exit onto either the body surface or an internal body cavity. An example of a gland utilizing merocrine secretion is the salivary glands, which produce saliva. Holocrine secretion, where the whole cell ruptures and dies, can be seen where glandular epithelial cells break off into the duct, rupture, and die while secreting their products. An example of this is the sebaceous gland, which secretes oil.

Lastly, apocrine secretion is demonstrated on the far right, where the entire apical portion of the cell sheds off but the cells do not die, unlike in holocrine secretion. A classic example of a gland utilizing apocrine secretion is the mammary gland. This concludes our brief lesson on multicellular exocrine glands and their modes of secretion, providing a foundation to apply these concepts moving forward. 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.

Here’s what students ask on this topic:

What is the difference between exocrine and endocrine glands?

Exocrine and endocrine glands are both types of glandular epithelial tissue, but they differ in their methods of secretion. Exocrine glands release their products through ducts onto body surfaces or into body cavities. Examples include sweat, oil, and salivary glands. In contrast, endocrine glands secrete hormones directly into the bloodstream, allowing these hormones to travel to distant organs and tissues. Examples of endocrine glands include the thyroid and adrenal glands. The key distinction is that exocrine glands use ducts for secretion, while endocrine glands do not.

What are goblet cells and where are they found?

Goblet cells are unicellular exocrine glands named for their goblet-like shape. They are primarily found in the epithelial lining of the respiratory and intestinal tracts. Goblet cells secrete mucin, a glycoprotein that forms mucus when hydrated. This mucus serves to lubricate and protect the epithelial tissue. Goblet cells are typically located among columnar cells, which are tall and narrow, and they release their mucin via exocytosis.

What are the three modes of secretion in multicellular exocrine glands?

Multicellular exocrine glands can secrete their products through three different modes: merocrine, holocrine, and apocrine secretion. Merocrine secretion, the most common type, involves exocytosis, where secretory vesicles release their contents without harming the cell. Holocrine secretion involves the entire cell rupturing and dying to release its product, as seen in sebaceous glands. Apocrine secretion involves the apical portion of the cell shedding off to release its product, without the cell dying, as seen in mammary glands.

How do merocrine, holocrine, and apocrine secretions differ?

Merocrine secretion involves the release of products via exocytosis, where secretory vesicles fuse with the cell membrane to expel their contents. Holocrine secretion involves the entire cell rupturing and dying to release its product, necessitating the replacement of the dead cells. Apocrine secretion involves the apical portion of the cell shedding off to release its product, but the cell itself does not die. These modes of secretion are exemplified by salivary glands (merocrine), sebaceous glands (holocrine), and mammary glands (apocrine).

What is the function of mucin secreted by goblet cells?

Mucin is a glycoprotein secreted by goblet cells, which are unicellular exocrine glands found in the respiratory and intestinal tracts. When mucin is hydrated, it forms mucus. The primary functions of mucus are to lubricate and protect the epithelial tissue. In the respiratory tract, mucus traps dust, microbes, and other particles, preventing them from reaching the lungs. In the intestinal tract, mucus facilitates the smooth passage of food and protects the lining from digestive enzymes and acidic conditions.