Connective Tissue Proper: Loose Connective Tissue - Video Tutorials & Practice Problems

Loose Connective Tissue

In this video, we're going to continue to talk about connective tissue proper as we begin our lesson on loose connective tissue and so loose connective tissue as its name implies is going to be a connective tissue named for its loose arrangement of protein fibers found in the extracellular matrix. Now, loose connective tissues are often going to be vascular, which means that often loose connective tissues are going to have blood vessels in them. Now, loose connective tissue is commonly known as the packing material of the human body. And this is because loose connective tissues are found all throughout the body in various locations including in the spaces in between organs as well as underneath of the epithelia throughout pretty much the entire body and it can form the internal structural framework inside of some organ. Now, really there are three different types of loose connective tissue. And so those three different types of loose connective tissue are Ariola, connective tissue, reticular connective tissue and adipose connective tissue. And so moving forward in our course, in different videos, we're going to talk a lot more details about each of these three different types of loose connective tissue Now, it is worth noting that these three types of loose connective tissue actually differ from each other in terms of their protein fiber arrangement in their extracellular matrix, in terms of the amount and the types. And they also differ from each other in terms of the cell types. And we'll be able to talk more about that as we move forward, talking about each of these three types in their own separate videos. And so notice down below what we have is the map of our lesson, which we've seen before in some of our previous lesson videos. And so again, we know that connected tissue can be grouped into two major classes, connected tissue proper or general or fibrous connected tissue and specialized connective tissue. Now we'll talk about the specialized connective tissues later in our course in different videos. Right now, we're focused on connective tissue proper, more specifically the loose connective tissues. Uh And of course, we've introduced here that there are three different types of loose connective tissues, including Ariola, connective tissue, reticular connective tissue, and adipose connective tissue. And so once again, we'll talk about each of those three different types of loose connective tissues moving forward in our course. But for now, this year concludes our brief introduction to loose connective tissues. And so I'll see you all in our next video to talk more details about alar connective tissue

Areolar Connective Tissue

In this video, we're going to talk about the first type of loose connective tissue in our lesson, which is areolar connective tissue. And so the word Ariola is actually a Latin term that means small open spaces. And so what you'll notice is down below in the micrograph of AOL or connective tissue, there appear to be all of these small open spaces or pores throughout the entire tissue. And so this is a direct result of the loosely arranged protein fibers in the extracellular matrix. And so notice that all of these lines that are striking through this micrograph here are all of the protein fibers in the extracellular matrix and notice that these protein fibers are all loosely arranged in aerial or connective tissue in such a way that it appears to create all of these small open spaces. And so hopefully all of this is a helpful reminder for you that aerial or connective tissue is a type of loose connective tissue with these loosely arranged fibers that seem to create all of these small open spaces in aerial or connective tissue. Now, aerial or connective tissue is actually the most widely distributed connective tissue in the human body. And so it can actually be found in pretty much all areas of the human body. Now, aerial or connective tissue is commonly referred to as the universal packing material of the human body. Again, because it's so widely distributed and can be found in areas such as the spaces in between organs. And so it can wrap those organs and cushion and bind those organs together. It can be found around blood vessels and nerves and muscles and aerial or connective tissue is also found supporting the epithelial tissue throughout pretty much the entire body. And so notice over here on the right, we have a diagram which is showing you the epithelial tissue here and notice that immediately beneath the epithelial tissue, we have the basement membrane and notice that immediately beneath the basement membrane is ollar connective tissue, a type of loose connective tissue. And recall from our previous lesson videos that often loose connective tissues are vascular and that does apply to AOL or connective tissue. It is vascular, which means that it contains blood vessels and those blood vessels in the AOL or connective tissue can support the avascular epithelia by providing nutrients and uh helping to eliminate waste. Now, in terms of the composition, areolar connective tissue actually has all three types of protein fibers, including collagen fibers, reticular fibers and elastic fibers. And that's going to contribute to its diverse functions. Now, also because aerial or connective tissue is a type of loose connective tissue and loose connective tissue is a type of connective tissue proper. Recall from our previous lesson videos that connective tissue proper tend to have a gelatinous ground substance that is a semifluid something in between a solid and a liquid. And so that means that the ground substance is going to be somewhat viscous or thick and that's going to create a somewhat thick matrix. Now, in terms of the composition of cells, aerial or connective tissues can have a bunch of different types of cells, including the fixed and resident cells associated with connective tissue proper, including fibroblasts, which are again are blast cells that are going to actively secrete and build components of the extracellular matrix, including the ground substance and the protein fibers. And it's also going to include fibrocyte which are going to be less active and are going to more maintain the extracellular matrix with minor repairs and routine maintenance. Now, aerial or connective tissue is also going to have migratory immune cells including mass cells which are going to release the chemical histamine that is important for inflammation. And also it includes the migratory macrophages, which are going to be important for phagocytosis, which is essentially engulfing pathogens for elimination. Also, aerial or connective tissue has adipocyte which are fat cells and these adipocyte are going to be considered a fixed or resident cell that is found in aerial or connective tissue. Now, these adipocyte which are fat cells again, they store fat molecules which can actually be used as a nutrient for a long term energy stored. And also those fat cells or adipocyte with all of that fat can provide insulation as well. Now, in terms of the functions, aerial or connective tissues have many different functions. But here in this video, we're going to focus on three main functions that they have. And so the first is supporting and binding. Again, we know that aerial or connective tissue is going to support the epithelial tissue cells. Again, aerial or connective tissue is vascular and so it can support the epithelial tissue. Since again, aerial or connective tissue is usually found immediately underneath of the epithelial cells right underneath of the basement membrane. And in terms of binding, again, aerial or connective tissue can be found in it's, it basically serves as the universal packing material. And so it can be found in the spaces in between organs and help to provide cushioning and bind those organs together. And also it can help to essentially bind the epithelial tissue. Uh The aerio uh connective tissue can bind the epithelial tissue to any underlying tissues that are beneath. Now, because arial or connective tissue has these m uh migratory immune cells, including mast cells and macrophages. It can actually be really important for protecting um and protecting against infection and invaders. And so this is also a really intuitive way to understand why aerial or connective tissue is found throughout the entire body because at any point in time, any location of our body can become infected. Or uh for example, if we get a cut in any region of our body, it can get infected. And so we need to be able to have aerial or connective tissue in many regions of our body. In order to help protect us against infection and also aerial or connective tissue because it does have these small spaces and pores. It can actually serve as a reservoir for water and fluids and nutrients. And so actually storing nutrients is a function of, of AOL or connective tissue. So it can store nutrients and fluids. And again, aerial or connective tissue is vascular, meaning it has blood vessels. And so those blood vessels deliver the nutrients to the aerial or connective tissue where those nutrients and fluids can be stored. And the aerial or connective tissue can supply nutrients and fluids to the epithelia, for example, and other surrounding tissues. Now, in terms of the locations, again, aerial or connective tissue, the universal packing material of the body is found all throughout the body in various locations, including underneath of the epithelia pretty much throughout the entire body. And so again, over here, you can see in the micrograph that these darker red spots are actually the nuclei of the cells, I likely the fibroblasts or the fibrocyte. And uh again, the fibers are going to be all of these lines that you can see striking through the extracellular matrix. And so this year concludes our lesson on AOL connective tissue. And as we move forward in our course, we'll be able to apply these concepts and problems and also learn more about other types of loose connective tissue. So I'll see you all in our next video.

Connective Tissue Proper: Loose Connective Tissue Example 1

So here we have an example problem that asks how does the structure of aerial or connective tissue help it act as packing material? And we've got these four potential answer options down below. Now, option A says that the ground substance holds fluid. And so recall from our previous lesson videos that Ariola is actually a Latin term for small open spaces which you can actually see under the light microscope is due to the loose arrangement of protein fibers in the extracellular matrix. And so because Ariola connective tissue has those small open spaces or that porous look to it, it's actually able to serve as a reservoir for nutrients and fluids. And also recall that aerial or connective tissue is a type of loose connective tissue which is a type of connective tissue proper. And recall from our previous lesson videos that connective tissue proper tends to have a gelatinous ground substance that is somewhat of a semifluid in between a solid and a liquid. And so because it does have this semifluid ground substance, it does allow the ground substance to store some fluid. And so option A is actually going to be true. Now, notice option B says a combination of branch and straight fibers create shrink. Now, recall from our previous lesson video that ollar connective tissue actually has all three of the protein fibers in its extracellular matrix, including collagen fibers, reticular fibers and elastic fibers. And recall that the term reticular in reticular fibers is a term that means netlike and so that reminds us that reticular fibers have collagen proteins arranged in a net like or a branched fashion. And so for sure, we know it's going to have branched fibers and also elastic fibers can also be branched and wavy. Now, we know that collagen fibers are actually going to have their collagen proteins arranged in an unbranded or straight pattern. And so, of course, this means that a combination of branch and straight fibers are going to be present and that's going to help create strength because having straight fibers like collagen fibers creates strength in one particular direction in terms of how that it's arranged and branched fibers can actually create resistance to forces in multiple directions. And so that's going to give it a lot of strength and a lot of versatility. And so option B is also going to be true. And so notice, option C says the presence of adipocyte acts as cushions and recall that adipocyte are fat cells that store lipids. And so those lipids can actually serve as long term energy storage and they can help provide a cushion and insulation and So these adipocyte are found in aerial or connective tissue. And so also option C is correct as well. And so this means that answer, option D, all of the above is going to be the correct answer for this example problem. And so all of these are going to help aerial or connective tissue have the properties that it needs to serve as the universal packing material in the human body. So that concludes this example and I'll see you all in our next video.

Reticular Connective Tissue

In this video, we're going to talk about the second type of loose connective tissue in our lesson, which is reticular connective tissue. And so recall from our previous lesson videos that one of the three protein fibers that can be found in the extracellular matrix are reticular protein fibers. And so it's no surprise that reticular connective tissue is only going to have those reticular protein fibers in its extracellular matrix, which is why reticular connective tissue is called reticular. And also this is why the fibroblasts of reticular connective tissue are actually called reticular cells because again, these reticular cells only produce those reticular protein fibers in the extracellular matrix. Now, because there are only reticular fibers in the extracellular matrix of reticular connective tissue. What this means is that the other two types of protein fibers including collagen fibers and elastic fibers are not found in their extracellular matrix, which means that the extracellular matrix of reticular connective tissue is going to have a lack of structural diversity and that lack of structural diversity is going to lead to a lack of functional diversity in reticular connective tissue as well. Now recall that the term reticular is actually a term that means netlike. And so this reminds us that those reticular protein fibers are going to have those collagen proteins arranged in a net like or a branched structure. And that branch structure actually allows it to resist forces in multiple directions, which is really important for being able to provide structural support. And so reticular connective tissue is going to be important for providing structural support by again using its branch reticular protein fibers in its extracellular matrix. Now, in addition to the reticular cells and reticular connective tissue, there can also be a host of other migratory immune cells in reticular connective tissue as well. Now, in terms of the functions of reticular connective tissue. Here in this video, we're only going to focus on one main function of reticular connective tissue. And that is going to be that reticular connective tissue forms the internal scaffolding for soft organs such as for example, the lymph nodes, the spleen, the liver, the kidneys, the thymus and the bone marrow, for example. And so because reticular connective tissue does form the internal scaffolding, providing structural support in these soft organs. It means that reticular connective tissue is going to support the functions of each of these soft organs. For example, reticular connective tissue with its branched reticular fibers can actually be used to filter dead blood cells in the spleen. And it can also be used to filter microbes in the lymph nodes, for example. And in the bone marrow, reticular connective tissue is going to provide the structural framework for um hematopoiesis to occur, which is actually the process of uh blood formation, which again occurs in the bone marrow. And so again, what we're saying here is that reticular connective tissue because it provides that structural support and that internal scaffolding uh framework inside of these soft organs, it's going to support the functions of each of these organs. And so notice over here on the right, we're showing you an image of a person and you can see the lymphatic vessels going through this person here and each of these bulges that you can see throughout the lymphatic vessels represent lymph nodes. And again, we know that reticular connective tissue is going to form the internal structural framework of these lymph nodes as well as the bone marrow. And the bone marrow is found inside of the bones. As you can see in this little uh image. It's also going to form the internal structural framework of the kidneys of the spleen, the liver and the thymus as well. And so notice here we have a micrograph that's showing you reticular connective tissue where you can see all of these reticular cells. And in some micrograph, you're actually able to see the reticular fibers that are branching through the uh extracellular matrix with the proper staining for certain you can see them. And in this particular micrograph, they're a little bit harder to see but they can be seen. And so this year concludes our lesson on reticular connective tissue. And as we move forward in our course, we'll be able to apply these concepts and learn more about other types of loose connective tissue. So I'll see you all in our next video.

Adipose Connective Tissue

In this video, we're going to talk about the third loose connective tissue in our lesson, which is adipose connective tissue. And so as its name implies with the term adipose, adipose connective tissue is going to be composed mostly of adipose sites which recall from our previous lesson, videos are fat cells that store fats or glycerides as these relatively large lipid droplets that take up most of the volume of the adipocyte and push off its cytoplasm and organelles including its nucleus off to the periphery or the perimeter of the adipocyte. And so notice if we take a look at this micrograph of adipose connective tissue that the adipocyte or fat cells are being indicated as these circular white cells that you can see throughout the tissue. And so the white component of these cells is actually that relatively large lipid droplet made of fats or triglycerides that again takes up most of the volume of the adipocyte and pushes off its cytoplasm and organelles including the nucleus off to the periphery or the perimeter of the cell. And although that's the case, these adipocyte are still functional cells and so they can still secrete components including components of the extracellular matrix such as ground substance and protein fibers. However, the extracellular matrix and adipose connective tissue is going to be sparse. And so it does have a sparse matrix which means that it has relatively little extracellular matrix. And so that's why these adipocyte in the adipose connective tissue appear to be really tightly packed together as you can see in the micrograph. However, although they appear to be really tightly packed together, these cells are still very loosely arranged, which is why this is a loose connective tissue. And so each of these adipocyte, although they appear to be tightly packed together, they can actually enlarge in their size as their lipid droplet enlarges when they store more lipids or more fats. And they can also decrease in their size as they release fats to the body, which can be used as energy in other locations of the body. And so it's important to note that adipose connective tissue is actually a highly vascularized tissue, which means that it's going to have many, many blood vessels, which is really important for the adipose connective tissue to receive nutrients that it can ultimately store as fats or lipids in the lipid droplet. And it's also important for the adipose connective tissue to release lipids or fats into the bloodstream, which again can be transported to other areas of the body and utilized as energy. And so really one of the most important characteristics to note about adipose connective tissue is that it is able to store energy by storing these lipid or fat or triglyceride molecules. And also those lipids can, can serve to insulate the body to keep it warm due to its high adipocyte content. Again, lots and lots of adipocyte, storing lots of fat. And so it can also provide a cushion in order to serve some protective features as well. And so in terms of the functions, uh adipose tissue can have many different functions. But here we are highlighting three main functions of adipose tissue. The first is going to be to store nutrients and energy. Again, we know that these adipocyte have a relatively large lipid droplet that is storing fats or triglycerides. And so it can actually store those uh molecules for a long period of time. And then it can release components of fats into the bloodstream where again, they can be transported to other areas of the body and utilized as energy when the body needs it. Now, another function of adipose tissue is that it is going to protect by absorbing shock. Again, it can provide some cushioning and that cushioning can help to provide a little bit of protection. And then the third function is that adipose connective tissue can serve to insulate the body and keep the body warm. And so we'll find that adipose connective tissue is actually found in the deep or or deep to the layers of the skin. And so you can see it's uh deep, it's gonna be found deep to the layers of the skin in the uh what's known as the subcutaneous layer. And so there it is actually going to help insulate the body and keep the body warm, preventing the body from losing too much heat. Um Now, the adipocyte or adipose tissue can actually be found in several different areas of the body. It can actually be found anywhere where alar connective tissue is found. And so we know alar connective tissue can be found all throughout the body. And so adipose tissue can also be found all throughout the body, including the abdomen or the stomach area, if you will around the eyes to provide cushioning and protection around the eyes and also around organs such as the kidneys and the heart, for example, which may need additional um you know, fat molecules for energy and even in the breasts, for example. And so notice over here in our diagram, we are showing you how uh in the top left, this is representing the skin. And what you'll notice is that the outermost layers of the skin are made of epithelial tissue immediately beneath that. We talked about how areolar connective tissue is supporting the epithelial tissue. That's a type of loose connective tissue. Then this darker blue area that you can see here that's actually representing dense irregular connective tissue, which we have not yet talked about. We'll talk about that later. In our course. But you'll notice that this is really the skin that layer there and then notice that immediately beneath the skin. This yellow layer here, this is the adipose connective tissue, which is found in the subcutaneous layer again, deep to the outermost layers of the skin here or deep to these particular layers that I indicated of the skin. Now, you can also find adipose tissue all throughout the body including around the eyes. Here. As you can see, these yellow areas represent adipose tissue again, providing cushioning and protection for the eyes. Um and it can also be found in the abdomen and it's found in all all people and it, it can also be found in uh regions of the body that are genetically uh controlled. And so uh some people can accumulate fat in areas such as underneath of their chin or in their back or uh in their hips and in their thighs and things like that. So it can have a genetic component to it in terms of where the adipose tissue tends to accumulate. And so this year concludes our lesson on adipose connective tissue. And we'll be able to get some practice applying these concepts and learn about two different types of adipose connective tissue as we move forward in our course. So I'll see you all in our next video.

Types of Adipose Tissue

In this video, we're going to talk about two different types of adipose tissue. The first being white, adipose tissue or white fat. And the second being brown adipose tissue or brown fat. And so the color of these tissues is not going to play a significant role in skin pigmentation or skin color. But instead the color of these tissues indicates what these tissues appear to look like under a light microscope. And so white, adipose tissue or white fat is going to appear white under a light microscope. Whereas brown adipose tissue or brown fat is going to have a more pigmented darker brownish color to it under a light microscope. And so in our last lesson video, the adipose connective tissue that we were mostly referring to was white, adipose tissue or white fat since this is actually the most abundant adipose tissue in adults. And so we already know that it's going to be important for storing energy since we know that adipocyte or fat cells can store fats or triglycerides as these relatively large lipid droplets. And we know that they can actually break down those lipids and release them into the bloodstream where they can be transported all throughout the body and be utilized as an energy source. And so for sure, it can store energy in that fashion. And we know that it can be found below the skin all throughout the body in regions known as the subcutaneous layer, which we'll get to talk more about later in our course. And it can also be found in the visceral layer around some organs such as for example, the kidney and the heart. For example. Now what's important to note is that adipocyte actually do not grow in the traditional way that you might expect cells to grow through cell division. And so adipocyte will actually grow in their size but not via cell division. And so there are precursor cells that can differentiate into adipocyte to create more adipocyte. But again, mature adipocyte do not go through cell division in the traditional way to create more adipocyte. Instead mature adipocyte again, are going to grow in their size. And so they can actually grow in their size and allow the lipid droplet to also grow in its size. And so when a surgery such as liposuction occurs where it is going to essentially suck out all of the or most of the adipose tissue in regions of the body. Although a lot of the adipose tissue is going to be removed, the remaining adipose tissue and the remaining adipocyte are still able to enlarge in their size. And so it is still possible for people to gain weight even after a surgery such as liposuction that removes a lot of the adipose tissue. Now, when it comes to brown adipose tissue or brown fat, it can still be found in limited amounts in specific regions of adults. However, brown adipose tissue or brown fat is going to be much more common in infants or babies. And so the reason that brown adipose tissue or brown fat has this brownish coloration to it is because it's actually going to be even more highly vascularized than white adipose tissue. And the brown adipose tissue tend to have mitochondria that are pigmented. And those mitochondria are going to be uh generating lots and lots of heat. And so what you can see here is that we can say that there are going to be lots of mitochondria or many mitochondria. And uh that many mitochondria content again is going to generate lots and lots of heat. And that is going to keep infants and babies warm because uh infants don't really have that shivering reflex to generate heat. And so they do rely more on the brown adipose tissue to keep them warm. And so notice over here in our diagram on the left, we're showing you an adipocyte of white adipose tissue and notice that they have this one relatively large lipid droplet that's taking up the vast majority of the cell. But in brown fat, you'll notice that the lipid droplets droplets tend to be smaller and more numerous. And the lipid droplets are more so going to be used for uh providing energy to those mitochondria. And uh notice that there are a lot more mitochondria in the brown fat than there are in the white fat. And again, those mitochondria and the brown fat are going to generate lots of heat to keep infants warm. And so notice down below, we've got this micrograph and you can see that again, the cells that appear whiter here that is going to be the white fat and then the darker, more pigmented fat that you can see up above that would be the brown fat. And so this here concludes our lesson on these two different types of adipose tissue and moving forward, we'll be able to apply these concepts in some problems. So I'll see you all in our next video.

Connective Tissue Proper: Loose Connective Tissue Example 2

In this video, we have an example problem that says if liposuction procedures remove adipose tissue, then why do patients report gaining weight back? And we've got these four potential answer options down below. And so it is true that liposuction surgery or procedures remove adipose tissue. However, they do not remove all of the adipose tissue because some adipose tissue is critical for the healthy functioning of the body. And so the adipose tissue that remains is still capable of growing even after a liposuction procedure. But recall that the adipocyte or fat cells do not grow in the traditional sense through cell division, like most other cells do and instead mature adipocyte grow in terms of their size rather than growing through cell division. And so after a liposuction surgery or procedure, if the patient doesn't maintain a healthy lifestyle, including a healthy diet and regular exercise, it is possible for the adipocyte and the remaining adipose tissue to grow in their size. And so notice answer option A says because adipocyte undergo cell division and again, mature adipocyte don't really grow via cell division like other cells typically do. And so for that reason, we can eliminate answer option. A option B says that because adipose tissue is avascular, but recall that adipose tissue is actually highly vascularized, which means that it has a lot of blood vessels. And so to say that it is avascular is incorrect. Then notice that answer option D says because adipose tissue holds more water. But we know adipose tissue has mostly adipocyte which have lots of lipid droplets and lipids are hydrophobic or water fearing. And so that is not going to be a feature that allows this tissue to hold more water. And so for that reason, we can eliminate option D. And so of course, answer option C here is going to be the correct answer which says that because adipocyte can increase in their size. And again, that is going to be the correct answer here. So c here is correct and that concludes this example. So I'll see you all in our next video.

Review of Loose Connective Tissues

In this video, we're going to do a review of the three different types of loose connective tissues. And so because this video is a review, what that means is that there's no new information covered in this video that we haven't already covered in our previous lesson videos. And so if you're already feeling really good about loose connective tissues, then you can feel free to skip this video if you'd like. But if you're looking for a little bit of review, then stick around because this video could be really helpful for you. And so that being said, notice down below, we have a table of the three different types of loose connective tissue where in the far left column, we have the type of loose connective tissue. The next column has some key characteristics of the tissue. The following column has some key important functions of the connective tissue. And then the last column has some example locations of where the connective tissue can be found in the human body. And so recall from our previous lesson videos that the first type of loose connective tissue that we covered in our lesson was Ariola connective tissue and recall that the term Ariola is actually a Latin term that means small open spaces. And so when you look at the micrograph of aerio connective tissue, you can see that the protein fibers are loosely arranged, creating those small open spaces or that porous look to this alar connective tissue. Now recall that aerial or connective tissue is actually the most widely distributed connective tissue throughout the entire human body and can be practically found in all areas of the body. And so this is why AOL or connective tissue is known as the human body's universal packing material. Now, in terms of its characteristics, aerial or connective tissue is going to have a viscous or a gelatinous extracellular matrix. That is going to be a semifluid something in between a solid and a liquid and aerial or connective tissue is going to have all three of the protein fibers in its extracellular matrix, including collagen fibers, reticular fibers and elastic fibers. And because it has so much structural diversity in its extracellular matrix that's also going to contribute to its functional diversity as well. And so it has a lot of different functions. Now, in terms of its cell types, mostly uh aerial or connective tissue is going to have fibroblasts, which recall are the cells that actively build and secrete components of the extracellular matrix. However, it can also have fibrocyte which can maintain the extracellular matrix through minor repairs and routine maintenance. And they can also have these migratory immune cells such as macrophages which perform phagocytosis or engulfing of invaders for elimination. And also they can contain those mass cells which are going to release the chemical histamine, which can cause inflammation and again help to eliminate invaders. Now, aero or connective tissue can also have adipocyte wherever aero or connective tissue is found. Adipocyte can also be found and recall adipocyte are fat cells that can actually store fats or triglycerides. And so in terms of the function, notice that it can have many different functions, but we focus on these three specific ones. The first being support and binding. We know that aerial or connective tissue can actually be found underneath of the epithelia throughout the entire body. And so notice here we have a diagram where we have the epithelial tissue. And of course, we have the basement membrane immediately beneath. But then notice that below that we have the ollar connective tissue which tends to be vascular or has lots of blood vessels, which allows it to support the avascular epithelia throughout the entire body. And also it can be found in the spaces between organs. Uh which is why again, it's known as the universal packing material where it can help to bind those organs together. Now, because aerio or connective tissue has these migratory immune cells like micro macrophages and mass cells. It can also help to defend against infection. And that is also a key reason why aerio connective tissue is found all throughout the body because at any point in time, any region of our body can become infected if it gets cut, for example. And so it's important to have aero connective tissue to help defend against infection throughout the entire body. And then again, because aerial or connective tissue has those small spaces and that porous look to it. It can actually serve as a reservoir for storing nutrients and fluids. And so it can actually provide nutrients and fluids to the surrounding tissues. And again, because aerial or connective tissue is vascular, it can receive nutrients from the blood, store those nutrients and fluids and then deliver those nutrients and fluids to the surrounding tissue such as the epithelia. For example. Now the next type of connective loose connective tissue that we covered in our lesson was reticular connective tissue and recall, reticular connective tissue is only going to have those reticular protein fibers in the extracellular matrix, which is why it's called reticular connective tissue. And why the fibroblasts of reticular connective tissue are called reticular cells because again, they only produce the reticular fibers. And that means that the collagen fibers and elastic fibers are not found in the extracellular matrix of reticular connective tissue. And so it has a lack of structural diversity in the extracellular matrix and that lack of structural diversity is also going to roll into a lack of functional diversity as well. Now, reticular connective tissue is going to have a viscous gelatinous or Gelli matrix that is a semifluid something in between a solid and a liquid. And in terms of its functions, we focus on the main function here, which is that it can serve as the internal scaffolding for many soft organs, including the lymph nodes, the spleen the liver, the kidneys, the thymus, and the bone marrow. And so because it forms the internal scaffolding, providing structural support in these organs, it can actually help to support the functions of each of these organs. Now, the next or the last type of loose connective tissue that we talked about in our lesson was adipose connective tissue, which recall adipose connective tissue is going to be mostly made of adipocyte or fat cells that store fats or triglycerides as these relatively large lipid droplets within the cell that can take up the vast majority of the volume of the cell. And so uh the adipose connective tissue tends to have a sparse, a sparse uh viscous matrix. So it has relatively little extracellular matrix, which is what makes these adipocyte appear to be really tightly packed together. But again, these adipocyte are very loosely arranged, which is why it is a loose connective tissue. And so these cells, although they appear to be really tight packed together, they can easily enlarge in their size and they can also release lipids and decrease in size. And when they release those broken down lipids, those lipids can be essentially uh absorbed into the bloodstream and transported throughout the bloodstream to other areas of the body where those lipid components can serve as energy sources. And so uh adipose connective tissue is going to be highly vascularized, meaning it has lots and lots of blood vessels. And that allows the blood vessels to bring nutrients to the adipose tissue where it can essentially store those nutrients in the form of lipids. And again, it allows the adipocyte to break down their lipids and transport those broken down lipids in the blood to other areas of the body where those lipids can serve as an energy source. And so, in terms of the functions, again, it's going to be able to store nutrients and energy in the form of lipids, it's able to absorb shock since it can act as a cushion and uh help to protect. And it can also insulate by keeping the body warm. Uh since it's found in the layers underneath of the skin. And so again, it can be found deep to the layers of the skin. It can be found in areas of the body such as the abdomen or the stomach area. As you can see here in this little image, it can also be found around the eyes where it can provide cushioning and protection and around organs such as the kidneys in the heart. And it can also be found in the breast. And so um adipose connective tissue is also going to have a genetic component to it, that is going to determine where it can be found in the body. And so in some people, you can find that adipose connective tissue tends to accumulate under the chin or in the back or in areas such as the hips or the thighs, for example. And so this year concludes our brief review of the three different types of loose connective tissue. And as we move forward in our course, we'll be able to get some practice applying these concepts. So I'll see you all in our next video.

What part of areolar tissue allows it to protect against infection?

• A. Fibroblasts. 
• B. Fibrocytes.
• C. Adipocytes.
• D. Macrophages.

During a dissection, you are asked to identify a connective tissue with a gel like matrix that forms the inside structure of the spleen. What is the type of connective tissue?

• A. Areolar Connective Tissue. 
• B. Reticular Connective Tissue.
• C. Adipose Connective Tissue. 
• D. Cartilage.

How does areolar tissue and epithelial tissue work together to prevent infection?

• A. Both areolar tissue and epithelial tissue are richly supplied with blood, mast cells, and macrophages, providing defense against microbes. 
• B. Areolar tissue provides both the collagen that creates a barrier in epithelial tissue and the macrophage that travel through epithelial tissue defending against microbes.
• C. Epithelial tissue provides a tight barrier that microbes cannot pass. Areolar tissue contains immune cells for when that barrier is compromised. 
• D. Areolar tissue provides a tight barrier that microbes cannot pass and epithelial tissue sends signals directing the immune system where white blood cells are needed.

Max hears that wrinkles are formed because the dense irregular connective tissue under the skin produces less collagen as we age. To counteract this, they go out and buy a skin cream that claims to contain collagen fibers. Based on what you know about connective tissue and epithelial tissue, do you expect the collagen fibers in this hypothetical skin cream to affect the underlying connective tissue?

• A. Yes, because the collagen allows connective tissue to stretch, so supplementing with collagen fibers will allow the skin to stretch & tighten to remove wrinkles. 
• B. Yes, because epithelial tissue is specialized for absorption, so biological molecules like collagen fibers will be quickly integrated into areolar tissue.
• C. No, because areolar tissue mostly produces elastin, so the difference in collagen production is unlikely to affect wrinkles. 
• D. No, because stratified squamous epithelial tissue prevents the passage of most molecules, so the large collagen fibers will not reach the underlying areolar and dense irregular connective tissues.