This is 3.2 simple epithelial tissue notes. The essential question is what are the characteristics, functions, and locations of each type of epithelium. Call that every epithelium have a first name and a last name. Having the first name simple tells you that it's going to be a single layer. First epithelium is simple squamous epithelium.
The first name tells you that it is single layer. Simple means single. So you see that there is a single layer of cells.
The last name squamous tells you that these cells are going to be flat shaped. Sometimes you might not be able to see the outline or the shape of the cell but you will definitely see the shape of the nuclei. Nuclei is the plural form of the word nucleus and here you can see the squamous tells you that the nuclei are disc shape or flat. Because simple squamous epithelium is flat and single layer, they are very, very thin.
So it allows for materials pass through easily. So the functions of simple epithelium is diffusion, which means that material substance is passing from high concentration to a lower concentration, and filtration, which means that substance is passing through some type of a membrane, and the liquid and the solids are being separated. The locations of... The simple squamous epithelium is the alveoli or the air sacs of the lungs.
This is where the gas exchange occurs, so they have to be very thin so that oxygen and carbon dioxide can easily pass through. They could also be found in the lining of the heart, blood, and lymphatic vessels, but specifically in the blood and lymphatic capillaries, which are very, very thin. That's where gas exchange also occurs.
And they are found lining body cavities. Here's a diagram. on the left and an actual picture on the right of the simple epithelium.
And note that the epithelial portion of this tissue is right here. Okay, this is the only portion that is the actual epithelium. The rest of this material here is actually connective tissue and not part of the epithelium.
You know that this is simple squamous epithelium because you see that there is only one layer. of epithelium and I can see that the cells are flat. Another indication that this is a simple squamous is that the nuclei are all disc shaped. You must also be able to identify three structures in a picture of a tissue.
One of those things is The apical surface, so this portion here, the top layer, or the portion that is not attached to anything, that's your apical surface. The portion that is actually attached to the underlying connective tissue is the basement membrane. And the last structure you need to identify are the nuclei.
Second type of epithelium is the simple cuboidal epithelium. Again, simple means one layer, but the last name tells you, cuboidal tells you that they are cube-shaped or square-shaped. And when you look at the nuclei, they're going to be round or spherical.
The functions of the simple cuboidal epithelium is going to be secretion, which means they're going to produce something and release them. They could also be involved in transportations in such organs as glands. And they could also be involved in filtration in the kidneys.
The locations for simple cuboidal is the kidney tubules, which are the tiny tubes inside the kidneys, and also the ovaries, the surface of the ovaries and their common type of epithelium-founding glands. Here is a diagram of simple cuboidal epithelium. The first thing you need to do is be able to identify where the actual tissue is, and it is surrounding this opening. Remember, epithelium always has to have one side that is exposed to the outside.
What you are looking at is looking through down the barrel of a tube. And so this white area here is the empty space inside the tube. And this space is called the lumen.
Again the area that is not touching another tissue. This is what's called an apical surface. Then you can kind of see the individual shape of the cell which is somewhat cube shape. And there is only one layer.
And the shape of the nuclei, majority of them are round, even though some of them are kind of squished. They are round or spherical shaped. The portion that is actually attached to the connective tissue, this area in the blue, is connective tissue. The portion that is attached to the connective tissue is called the basement membrane.
The third type of... Epithelium is the simple columnar epithelium. Simple tells you it's one layer. Columnar tells you that the cells are going to be tall and the nuclei are going to be oval shaped.
And the thing about simple columnar that you might see structure called cilia or microvilli. Cilia are tiny short hair like structures on the surface of the epithelium or lining of the epithelium. And microvilli are a little bit bigger and they're more like a thicker finger-like structures.
And their job is to increase surface area. Cilia is there to kind of sweep things along. Whereas microvilli is for absorption and increase in surface area gives it more areas for things to be absorbed through. Here is a picture of a simple columnar cell.
And notice that they are... Tall cells, column shaped. They have one row of nuclei. That kind of tells you that that is a single layer, simple. And they have cilia or microvilli on the apical surface.
The surface that is not attached to another tissue. Another unique thing about simple columnar cells, they have something called the goblet cells, and their job is to produce mucus. Function of...
The simple columnar epithelium is absorption. Again, absorption means sucking some type of fluid or chemical through a wall. Secretion of mucus and if they have cilia, the cilia aids in moving something along down usually when this epithelium is lining a tube.
Locations where simple columnar epithelium can be found is lining small tubes in the lungs. Or they could be found in the female reproductive organs such as the uterine tube and the uterus. And the most common place you will find them is the digestive tract.
Here is a diagram of the simple columnar epithelium. Notice that the cells are tall. They're lined up, standing straight tall. And you can see the nuclei are standing and they're oval-shaped.
Okay, those are your nuclei. The basement membrane is here, okay, because this lavender area right here is your connective tissue. So again, basement membrane is right there and right here. The apical surface is the surface that contains the cilia. That's your apical surface.
And this one is the microvilli. You can see the microvilli. And then these structures here. Sometimes they'll look like empty spaces like this here.
Those are your goblet cells. The last simple epithelium is pseudostratified columnar epithelium. The prefix pseudo means false, stratified means layer. So literally pseudostratified means false layer.
The reason for this name is that this epithelium has the appearance of layers but it is still considered one layer. Notice that this is a columnar cell which means that they have Goblet cells and they have cilia because this one is a columnar cells you might mistake pseudostratified with simple columnar epithelium and the way you're going to tell those apart is has to do with the varying heights of the nuclei in the simple columnar the Nuclei are all in a row, but in pseudostratified they can be staggered There is a picture of pseudostratified epithelium. Notice that the first cell looks a lot like simple columnar, but notice the other cells are not perfect rectangular shape. Okay, and some of the cells will not start at the basement membrane and go all the way to the top.
Notice how this one starts at the basement membrane. They kind of taper off and they don't quite reach the apical surface. Another thing you'll notice is the nuclei are kind of staggered. Notice this one is on the bottom, this one's at top, this one's the bottom again, this one is the top, bottom, bottom, so they are staggered.
The nuclei are staggered. But just like simple columnar, they do have cilia on its apical surface. Locations where you might find pseudostratified columnar epithelium is the male reproductive tubes and the trachea, which is the windpipe and the upper airways.
And in that area, that's where you're going to have the cilia. And so the name of that type of tissue would be ciliated pseudostratified columnar epithelium. Here's another picture of pseudostratified columnar epithelium. Here is the basement membrane again.
Here is the apical surface. The apical surface have cilia. You notice the goblet cells, spaces. Notice they're like lighter in color. Those are your goblet cells.
And notice the nuclei are kind of almost stacked on top of each other. Some of those, like this cell right here, doesn't go all the way to the top, and they're kind of not all lined up. The nuclei are not lined up. Some are toward the apical surface, and they're toward the bottom, too. The 3.2 notes homework is, number one, where in the body is ciliated pseudostratified columnar epithelium found?
Number two, what type of tissue is found in the digestive tract? And number three, what is the most common tissue found in glands?