Introduction to Epithelial Tissue - Video Tutorials & Practice Problems
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concept
Intro to Epithelia
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3m
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In this video, we're going to begin our introduction to epithelial tissue. And so, recall from our previous lesson videos that epithelial tissue is one of just four primary types of tissue found in the human body. And epithelial tissue is commonly abbreviated as just epithelia without the L and without the tissue. And so, epithelia or epithelial tissue is tissue that covers body surfaces and many organs, lines, internal body cavities and ducts and makes up glands or cellular structures that are specialized for secretion or releasing products. And so covering lining and glands are key terms that are very often associated with epithelial tissue in your textbooks. However, one of the key defining features of most epithelial tissue is that it consists of a single sheet or multiple sheets of tightly packed cells on a boundary immediately adjacent to open space. In fact, if we take a look at our illustration down below, you'll notice that we're highlighting a few examples of where epithelial tissue can be found in the human body. And what you'll notice is that in each of the micro graphs, for these examples, we can clearly see that epithelial tissue is going to consist of sheets of tightly packed cells on a boundary adjacent to open space. In fact, we can actually highlight the open space in each of these micro graphs. And so notice on the far left over here, you can see the open space is right here in this region. In the second micrograph, you can see that there's open space right over here. In this third micrograph, you can see that there's small bits of open space in these highlighted small regions that you see there. And then in this final micrograph, once again, you can see that there's small bits of open space in these highlighted regions right there. And so over here in the micrograph, on the far left, notice that it is indicating that the outermost layers of our skin is going to be epithelial tissue. And we know that our skin covers our entire body surface. And so the outermost layers of the skin is a classic example of epithelial tissue. Now, we also know that epithelial tissue is going to be important for lining internal body cavities, including lining of our airways. And so notice that this second example is showing that the lining of our airways is going to contain epithelial tissue. And we also know that epithelial tissue is important for forming or making glands. And so that's going to include salivary glands and salivary glands are going to be found in our mouth and they are going to secrete or produce saliva And then last but not least we know that epithelial tissue is important for uh lining ducts and forming tubules as well. And so notice in this last example, we're showing you that the ducts and tubules found in our kidney are going to contain epithelial tissue. And so once again, this is just our brief introduction to epithelial tissue. And as we move forward in our course, we're going to continue to learn a lot more about epithelial tissue. And so this concludes this introduction and I'll see you in the next video where we'll talk more about the functions of epithelial tissue.
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concept
Functions of Epithelial Tissue
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7m
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In this video, we're going to begin our lesson on the functions of epithelial tissue. And so before we get started, it's important to note that the functions of epithelial tissue are pretty diverse. And so there are a bunch of different functions. And so instead of making an exhaustive list of all of the different functions of epithelial tissue. In this video, we're going to do more of a big picture view and talk more broadly about the functions of epithelial tissue. And so that being said, epithelial tissue can be broadly categorized into two major functional groups with the indicated functions that you can see down below in our image. And so those two major functional groups are number one covering and lining epithelium, which you can see is over here in this far left block. And number two glandular epithelium, which you can see is over here in this far right block. And so covering and lining epithelium as its name implies, is going to be important for covering body surfaces and many organs and lining internal body cavities and ducts. And so for the functions of covering and lining epithelial tissue, it can actually be grouped into three major functions that you can see down below in our image. And so the first major function is going to be provide protection. And so once again, covering and lining epithelium is going to be covering things and lining things and it's going to serve as tissue on a boundary. And so this tissue on a boundary can provide protection, essentially acting as a physical barrier. You can think of it pretty much as a shield that's going to be protecting against things such as mechanical stresses and pressures, microorganisms such as bacteria, preventing the bacteria uh from getting into certain regions of our body and protecting other tissues against really hot and cold things. Now, the next function that we have here is regulating transport. And so once again, covering and lining epithelium is going to serve as tissue on a boundary. And so when we're talking about regulating transport, we're really talking about regulating the transport of substances across this tissue that's serving as a boundary. And so this covering and lining epithelial tissue that's serving as a boundary in regulating transport can be selectively permeable, which you might recall from our previous lesson videos when we were talking about membranes just means that it's going to be really picky about what substances it allows to cross through this tissue serving as a boundary. And so some substances will be able to cross more easily than others, other substances when it is selectively permeable. And so if we take a look at this little image, that's right here, notice that we've got this thin layer of epithelial tissue covering and lining epithelial tissue. And it is going to be regulating transport and it's serving as tissue on a boundary. And so you can see up above what we have is open space and down below what we have is deeper tissues. And so this covering and lining epithelial tissue that's serving as a boundary is going to be regulating the transport of substances across the tissue and into the open space, but also regulating the transport of substances from the open space across the tissue deeper into the tissue. And so this leads us to these three terms that you should be at least lightly familiar with. And those are absorption, excretion and filtration. And so absorption is a term that refers to the uptake of nutrients. And so, for example, the covering and lining epithelial tissue that lines our digestive system can absorb nutrients such as glucose from our diet. Now, excretion is essentially the opposite of absorption instead of uptaking nutrients, it's going to be releasing wastes. And so, for example, we can release waste uh and have them be excreted through the urine. And filtration is a term that refers to separating substances. And this is a key feature of the kidneys and something that we'll get to talk more details about much later in our course. Now the third function here of covering and lining epithelium is actually to allow sensations. And this is going to be in close connection with nervous tissue. And so allowing sensations is actually the primary function of nervous tissue. However, recall that covering and lining epithelial tissue is going to serve as tissue on a boundary. Um and it is going to essentially line our uh our external body. And so, epithelial tissue makes up the outermost layers of our skin. And so the epithelial tissue is really what connects us to the outside world. It's in direct contact with the outside world. And so it can be heavily involved in detecting initial stimuli from the outside world and then activating the nervous tissue to allow for the sensations to occur. And so, for example, some sensations such as touch, for example, when we go to touch things, uh the pressure can be detected by the epithelial tissue. And then once that epithelial tissue detects the pressure, it can go on to activate the nervous tissue, which can conduct an electrical signal and allow for the processing of that signal. And ultimately the sensation. Uh and so really, uh some sensations such as touch involve the epithelium and nervous tissue. And so, allowing sensations is a notable function of covering and lining epithelial tissue. And so really, that's it for our covering and lining epithelial tissue. So we can move on to our second major functional group, which is the glandular epithelium. And as its name implies glandular epithelium is going to be important for forming glands which again are going to be cellular structures that are specialized for secretions, producing secretions and secretions are really just uh products that are going to be released. And these secretions are again released via gland. And down below what we have here is an image uh that is supposed to represent a gland. So you can see this glandular epithelial tissue right here And the cells within the glandular epithelial tissue are going to be producing secretions, releasing the secretions or the products into this open space that you see over here. And so down below what we have are some examples of secretions that can be produced by glandular epithelium. And so things such as sweat, saliva, milk or oil, enzymes, hormones and mucus are all examples of secretions produced by glandular epithelium. And so this year concludes our brief introduction to the functions of epithelial tissue. And once again, we'll be able to learn a lot more about epithelial tissue as we move forward and we'll be able to get some practice applying these concepts as well. So I'll see you all in our next video.
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example
Introduction to Epithelial Tissue Example 1
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5m
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So here we have an example problem that says to use an X to indicate the primary function or functions associated with the epithelium in each body location. And so notice that we've got the body location listed in the far left column and we've got the functions from our last lesson video listed across the top. And so if we take a look at our very first body location, we can see that it is the skin. And so we know that the outermost layers of our skin is going to be covering and lining epithelial tissue. And we know that the skin is going to cover our entire body surface. And so the skin is going to have a primary function of protection. It is going to protect us from environmental factors such as for example, mechanical stresses and microorganisms that might try to penetrate into our body and cause this disease and it can also protect us from really hot or cold substances. Now, we also know from our last lesson video that the epithelia in our skin can also have an important role in sensation. And so recall that the epithelia in our skin connects us to the outside world. And so it can be important for detecting stimuli in the outside world, such as for example, touch or pressure or temperature. And the epithelia that detects those initial stimuli can then go on to activate nerve endings of nervous tissue that it is in close connection with to allow for sensation. And so we can indicate that protection and sensation are primary functions of the skin. Now, in terms of secretion, this is more of a function of glandular epithelial tissue. And so the sweat glands of our skin, that would be more so glandular epithelial tissue, but not so much the epithelial tissue in our skin, the covering and lining epithelial tissue in our skin. And then also in terms of transport, that's not really a primary function of the epithelial tissue in our skin, if anything, the skin is going to be preventing transport. But uh it does so in a protective manner, for example, preventing the transport of microorganisms in order to protect us from those microorganisms. So, moving on the next body location that we have here is the lining of the bladder, which we'll learn later in our course is also known as transitional epithelium or Euro thelium. And so the lining of our bladder is going to have a primary function of protection. Once again, its job is to essentially protect the rest of the body from the waste products that are found in the urine that can actually cause us damage and harm if that, if those waste products are reabsorbed into our body. And so the lining of the bladder is going to have a protective function. It's also going to have a uh primary function of sensation as well. And so there are nerve endings that are going to allow for us to detect if our bladder is full and needs to be empty. Now, in terms of secretions, again, that's more so of a uh glandular epithelial function, not a covering and lining epithelial function. And uh in terms of transport, regulating transport. Again, this is not a primary function of the lining of the bladder. Uh if anything, it is going to be preventing the transport of the urine, but in a protective fashion. Uh now moving on here, we have the capillary blood vessels and the capillary blood vessels is going to be lined with a very thin epithelium. And so that is going to be a lining epithelium. And uh the capillary blood vessels is going to have a primary function in regulating transport. And so, uh the capillary blood vessel epithelium is going to be regulating the transport of nutrients and gasses from the blood into the tissues, such as glucose being transported from the blood into the tissues and oxygen gas being transported from the blood into the tissues. And it will also regulate the transport of waste products from the tissues back into the blood, such as for example, carbon dioxide gas being produced by the tissues. It will regulate the transport of that CO2 back into the blood. Now, in terms of secretion, again, that's more of a function of glandular epithelial tissue, not lining, epithelial tissue, uh sensation, not really a primary function of capillary blood vessels and protection. Once again, probably not a primary function. It's more so regulating the transport, the exchange of materials between the blood and the tissue. Now, last but not least here, what we have is salivary, gland, and salivary gland. Uh It gives it away with this gland. Here it is going to be a glandular epithelial tissue. It's going to produce uh saliva in our mouth, which is going to have enzymes that help us break down our foods in our mouth and uh the salivary gland, uh of course, it's going to have a primary function of secretion. And so, uh in terms of these other functions, this is not really the primary function of salivary gland, it's mainly to secrete. And so this here concludes our brief example 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.
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Problem
Problem
Which statement is true about nearly all epithelial tissue?
A
All epithelial tissue produces specialized secretions.
B
All epithelial tissue has one surface that is adjacent to an open space.
C
All epithelial tissue consists of a thick layer of cells in order to provide protection.
D
All epithelial tissue allows for the diffusion of molecules into other adjacent tissues.
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Problem
Problem
When considering an internal organ like the heart or liver, based on what you know about epithelial tissue, do you think that most of the tissue that makes up that organ would be epithelial tissue or some other kind of tissue?
A
Mostly epithelial tissue.
B
Mostly some other kind of tissue.
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Problem
Problem
A nutrient in the small intestine is absorbed into the bloodstream. In doing so, it moves from being dissolved in the chyme present in the small intestine to being dissolved in the plasma of the blood. How many times did the nutrient pass through epithelial tissue when moving from the intestine to the blood?
A
0
B
1
C
2
D
3
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