Introduction to Connective Tissue - Online Tutor, Practice Problems & Exam Prep

Connective tissue is the most abundant and diverse tissue type in the body, characterized by a prominent extracellular matrix (ECM) that separates its cells. It serves various functions, including protection (e.g., bones safeguarding organs), transportation (e.g., blood carrying nutrients), binding and support (e.g., tendons and ligaments), insulation (e.g., adipose tissue), and storage (e.g., fat and minerals). Unlike epithelial tissue, which regulates transport and sensation, connective tissue primarily focuses on structural support and energy storage, highlighting its essential role in maintaining homeostasis.

Intro to Connective Tissue

So now that we've covered epithelial tissue in our previous lesson videos, in this video, we're going to begin our introduction to the second primary tissue in our lesson, which is connective tissue. Connective tissue is actually the most abundant and the most widely distributed tissue throughout the human body. We can pretty much find connective tissue in almost all areas of the human body. Connective tissue is also the most diverse tissue class amongst all four primary types of tissue, both in terms of its structure and its function.

Notice down below we are showing you these four micrographs that are all of connective tissues that we will get to talk more details about as we move forward in our course. But what you will notice is that just by looking at these four micrographs, you can clearly see that they are very different from one another. That goes to show how diverse of a tissue class connective tissue actually is. Notice the micrograph on the far left is actually showing us some connective tissue proper. The second micrograph is showing us some cartilage, which is also a type of connective tissue.

The third micrograph is showing us some bone, again, a type of connective tissue. And the fourth micrograph on the far right is showing us some blood, again, another type of connective tissue. We already know that our bones are really hard and solid structures, whereas our blood is actually a liquid.

This right here goes to show how diverse of a tissue class connective tissue actually is. However, despite all of the diversity of connective tissue, all connective tissues are going to have the following two things in common that we have numbered down below, number 1 and number 2. The first common feature of all connective tissues is that they are all derived from embryonic mesenchyme, which we covered briefly in some of our previous lesson videos. The second common feature of all connective tissue is that the cells of connective tissue actually occupy far less space than their ECM or their extracellular matrix, which takes up much more space in connective tissue. Unlike the cells of epithelial tissues, which we know from our previous lesson videos are really tightly packed or tightly pressed together with lots of tight junctions and desmosomes, and there's relatively little ECM between those cells, the cells of the connected tissue are not in direct contact with one another because they are spaced out or separated by the relatively large amounts of ECM or extracellular matrix.

In fact, connective tissue is unique amongst the four types of primary tissue in that the extracellular matrix can actually be significantly more prominent than the cells themselves. As we move forward in our course, we're going to talk more details about connective tissue. But this here concludes our introduction to connective tissue. In our next lesson video, we'll be able to focus on the structure of connective tissue. So I'll see you all there.

Structure of Connective Tissue

In this video, we're going to talk about the structure of connective tissue. Recall from our previous lesson videos that all tissues, including connective tissue, are made of groups of cells and their extracellular matrix, or their ECM. But recall that the extracellular matrix can be more prominent in some types of tissues versus other types of tissues. For example, recall from our previous lesson videos that epithelial tissue consists of cells that are really tightly packed together and have relatively little ECM between the cells. However, once again when it comes to connective tissues, they actually have the most prominent ECM or extracellular matrix that can take up most of the volume of the tissue and actually separate the cells because of the relatively large amounts of ECM.

Because connective tissue has the most prominent ECM, this is why we focus on its structure in this video. Recall that the extracellular matrix, or the ECM, is really just the material that is immediately outside of the cells. The extracellular matrix is made of ground substance and protein fibers. The ground substance is really just unstructured material that's between the tissue cells and between the protein fibers in the ECM. Depending on the type of connective tissue, the ground substance can actually range in its viscosity or range in its thickness from being a rock-hard solid, like bone, for example, to being a liquid like blood, for example.

The different types of protein fibers found in the extracellular matrix can contribute to the viscosity of the ground substance. Moving forward, we'll learn that there are three different types of protein fibers, and we'll talk about the differences in those three different types of protein fibers later in our course. But for now, you should note that the different types of fibers and the different amounts of each of those fibers can contribute to the tissue's physical properties, for example, contributing to the strength of the tissue, the flexibility of the tissue, and the ability for the tissue to recoil or spring back to its original shape. All tissues, including connective tissues, are made of groups of cells.

The cells of connective tissue can secrete and maintain the components of the extracellular matrix, including the ground substance and the protein fibers. Also, the cells will support the specialized functions of the connective tissue. In most types of connective tissue, there are two main types of cells, which are the blast cells and the site cells. The blast cells are going to end with the root "blast," which is why they're called blast cells. These blast cells are immature cells that have the ability to divide, and they are more active and actively build and secrete the components of the ECM.

Again, including the ground substance and the protein fibers. As we'll learn moving forward in our course, the blast cells of connective tissue proper are fibroblasts, which notice ends with the root "blast," again, which is why they are blast cells. Other examples of blast cells include osteoblasts, which are found in the bone, and chondroblasts, which are found in cartilage. The site cells are going to end in the root "site." These cells are more mature cells that are less active. They don't really divide as much, and they are more about maintaining the extracellular matrix rather than actively building and secreting the components of the extracellular matrix. In terms of maintenance, it's only going to do minor repairs and just routine maintenance. As we'll learn moving forward, an example of a site cell in connective tissue proper is going to be the fibrocytes, which notice ends in the root "sites," which is why they are site cells. Other types of site cells include osteocytes, which are found in bone, and chondrocytes, which are found in cartilage. If major or significant repair or growth of the tissue is needed, then sometimes these site cells can actually revert back to blast cells so that they can actively build and secrete the ECM for that significant repair and again that significant growth.

But, if it's really just maintaining the ECM, then it's just going to be minor repairs and again those would be the site cells. Notice down below we have an example and it's asking us how connective tissue is like ice cream with different toppings mixed in. Notice that we've got these two really delicious-looking ice cream cones down below, and what you'll notice is that we have the major components of the tissues here in the middle. Again, recall that all tissues are going to be composed of groups of cells, but also their extracellular matrix. We've learned that the extracellular matrix is going to be composed of round substance and protein fibers, or just fibers for short.

What you can see here is that we've got these key elements that are showing us how ice cream with different toppings mixed in is similar to connective tissue. The ground substance, the unstructured material between the cells and the protein fibers, is like the base of the ice cream, either a chocolate base or a vanilla base. Just changing the ground substance can change the tissue. The ground substance can change in viscosity or its thickness. It could be a rock-hard solid or a liquid. Just like ice cream, when you take it out of the freezer, it's kind of more rock-hard and more solid. Or if you have ice cream that's been left out for a little bit, it's kind of more liquidy. The protein fibers are going to be things such as chocolate swirls or caramel swirls or little candy cane swirls. There are three different types of fibers, and different amounts and different types of those fibers can contribute to the viscosity of the ground substance and also contribute to the physical properties of the connective tissue.

Every tissue is going to be composed of groups of cells. Those cells can be of different types and lead to different connective tissues. Notice we're using things like marshmallows, little chocolate chips, gummy bears, and sprinkles to represent the different types of cells. Notice that one ice cream with a chocolate base, marshmallows, and chocolate chips, and chocolate swirls as protein fibers will represent a different connective tissue compared to another vanilla-based ice cream here with little gummy bears, sprinkles, and candies as cells and little cotton candy swirls as the protein fibers. This is how connective tissue can resemble ice cream with different toppings and extent. As we move forward in our course, we'll be able to talk in more detail about connective tissue.

But for now, this here concludes our brief lesson on the structure of the connective tissue, and we'll be able to get some practice applying these concepts moving forward. So I'll see you all in our next video.

What part of connective tissue takes up most of the volume?

• A. Extracellular Matrix.
• B. Cells.
• C. Epithelium.
• D. Glands.

Functions of Connective Tissue

In this video, we're going to talk about some of the functions of connective tissue. Recall from our previous lesson videos that connective tissue is the most diverse class of tissue in terms of both its structures and its functions. It actually has a lot of different functions. Rather than making an exhaustive list of all the different functions of connective tissue, in this video, we're going to talk more broadly about the functions of connective tissue. As we move forward in our course, in different videos talking about specific types of connective tissue, then we can talk more about their specific functions.

But again, in this video, we're going to talk more broadly about the functions of connective tissue. Once again, it's important to emphasize that connective tissue functions are very diverse. They can be grouped into these five main functions that you can see down below in our image. Notice that the top layer of the image is listing the five functions. The middle layer here is showing a symbol or an image to support the function.

Toward the bottom, what we have are specific examples of the function. Notice that the very first function that we have here for connective tissue is that it can actually provide protection, similar to how armor can provide protection to what lies underneath. For example, bones such as the rock-hard skull, for example, can actually protect the soft structures that lie underneath such as the delicate brain. The next function that we have here is that connective tissue can transport materials, actually transporting the materials instead of just regulating the transport like what epithelial tissue does.

When we say transport materials, we can think of connective tissue such as blood, for example. Notice down below we are saying that blood can actually physically transport gases such as oxygen, for example, and nutrients such as glucose, for example. The blood can transport these gases and nutrients throughout the entire body to deliver oxygen and glucose to all tissues everywhere in the body. The blood can also transport wastes such as carbon dioxide from the tissues to the lungs where we can exhale that carbon dioxide. Transporting materials is a function of connective tissue.

Just like a car can transport materials, blood can also transport materials like gases and nutrients. The next function that we have here is more intuitive because connective tissue is going to be important for connecting or binding things together and is also going to be important for support. Binding and support is a function of connective tissue. In terms of binding, structures such as tendons, which are made of connective tissue, can bind or connect muscles to bones.

Ligaments, which are also made of connective tissue, can bind or connect bones to other bones. In terms of support, recall from our previous lesson videos that connective tissue supports epithelial tissue. Recall that epithelial tissue is avascular, which means that it does not have any blood vessels. It relies on the underlying vascular connective tissue that does have blood vessels. The vascular connective tissue with its blood vessels can supply the avascular epithelial tissue with nutrients such as glucose, for example, and gases such as oxygen.

It can also help eliminate the waste from the epithelial tissue as well. Notice that we're saying, in this little symbol or image here, notice that we've got some epithelial tissue highlighted here in green. Notice that this muscle man down below is just a silly way for us to say, this is the connective tissue that underlies the epithelial tissue that is actually supporting the epithelial tissue. You can think that this weight here is actually the basement membrane that separates the epithelial tissue from the underlying connective tissue. The next function that we have here is that connective tissue can actually offer insulation or it can insulate the body.

Connective tissue includes fat. Fat cells are called adipocytes. We'll talk about them later in our course. But connective tissue does include fat. Fat can help to insulate the body and keep the body warm, just like your winter coat can keep you warm during the winter when it's really cold outside. These fat cells or adipocytes, that store lots of fat can help with insulation and offer insulation to keep the body warm. The fifth and final function that we have listed here is to provide storage. It can store energy. Again, the fat cells can store fat and fat can serve as long-term energy storage.

Notice that we have these same fat cells here, these adipocytes. Just like a battery can store energy, these fat molecules can also be storing long-term energy. Another example is that bones can store calcium and phosphates. So when the body needs calcium and phosphates, it can use the bones as a reservoir for calcium and phosphates. We'll be able to talk about that later in our course.

But for now, this here concludes our brief lesson covering some of the functions of connective tissue. Again, as we move forward in our course talking about specific types of connective tissue, we'll get to talk more details about their specific functions. But for now, this here concludes this video, and I'll see you all in our next video.

Functions: Epithelial vs. Connective Tissue

In this video, we're going to briefly compare the functions of epithelial and connective tissues. We already know from our previous lesson videos that epithelial and connective tissues are both pretty diverse in terms of their functions. Because of this, some of their functions may seem to overlap a little bit. Therefore, we're going to compare their functions to clear up any potential confusion. Notice down below we have a three-column table with blanks, and we're going to fill out the blanks as we go through the video.

The middle column lists the functions of the tissues. Please remember that this is not an exhaustive list of all the different functions of these tissues; these are really just broader groupings of the functions of these tissues. In the column on the far left, we have examples of epithelial tissue functions, and in the column on the far right, we have examples of connective tissue functions.

The very first function listed here is protection. Recall from our previous lesson videos that epithelial tissue functions in protection. A classic example is the outermost layers of our skin, which protect us from the outside world, including physical trauma and chemicals.

Recall that the outermost layers of our skin are made of keratinized stratified squamous epithelia, which consists of multiple layers of cells where the cells on the apical surface are flat or squished in shape. The keratinized part of that means it's going to have the protein keratin, making the tissue tougher and aiding in protection. Connective tissue also functions in protection, as the rock-hard bones, such as the skull, help protect the delicate softer tissues underneath, like the brain.

In terms of transport, epithelial tissue can regulate transport. We're talking about epithelial tissue serving as the boundary adjacent to open space and can regulate the transport of molecules across the tissue for absorption, excretion, or filtration. A classic example of where regulating transport can occur is in the digestive lining, which contains simple columnar epithelia, or one layer of tall and narrow, column-shaped cells.

Connective tissue also functions in transport. Blood, for example, is an example of connective tissue, and we know that blood can physically transport things such as oxygen gas, nutrients like glucose, and waste products like carbon dioxide gas. The transport function here is different, with epithelial tissue more so regulating the transport of substances across the tissue, not physically transporting things.

In terms of sensations, epithelial tissue can work closely with nervous tissue to allow for sensation. Epithelial tissue connects us to the outside world since it covers and lines things such as our skin. Sensations such as touch can be detected by the epithelial tissue, which then activates the nervous tissue, and the nervous tissue transmits an electrical signal for processing, allowing for the full sensation. Connective tissue, although it can be innervated and contain nerves and nerve endings, is not usually associated with sensation functions due to its diverse functions and lack of connection to the outside world like epithelial tissue.

In terms of secretions, glandular epithelial tissue forms glands and these glands specialize in secreting products such as sweat, mucus, enzymes, and more. Connective tissue cells can secrete components of their own extracellular matrix, but do not specialize or form specialized secretions like glands do.

Support, insulation, and storage are not functions of epithelial tissues but are notable functions of connective tissue. The underlying connective tissue can be vascular, having blood vessels that provide nutrients and support the epithelial tissue. Connective tissue includes adipocytes (fat cells) which store fat that helps to insulate the body. Moreover, bones can store components like calcium, and adipocytes provide long-term energy storage.

This concludes our brief comparison of the functions of epithelial and connective tissue. Hopefully, this was helpful for you to understand the differences and similarities in their functions. That concludes this video, and I'll see you all in our next video.

Introduction to Connective Tissue Example 1

So here we have an example problem that's asking, what type of tissue is responsible for the support of the body? And we've got these 4 potential answer options down below. And so, of course, we know from our previous lesson videos that connective tissue does support the body. And so, we can go ahead and indicate that answer option b, connective tissue is the correct answer to this example problem. And so, recall from our previous lesson videos that connective tissue actually supports epithelial tissue.

Because recall, epithelial tissue is avascular, meaning it does not have any blood vessels. But the underlying connective tissue is vascular with blood vessels. Which means that the connective tissue can support epithelial tissue by providing nutrients and oxygen gas, for example. And of course, the connective tissue is going to support the epithelial tissue that's found throughout the body. And also, we know from our previous lesson videos that bones are a type of connective tissue.

And so, the bones that make up our skeleton are going to give our body the structure and support that it needs. And so that's another reason how we could've indicated option b, connective tissue is correct. Now, epithelial tissue is not going to function primarily in support of the body. Muscle tissue and nervous tissue, we have not yet talked about. So, we'll talk about muscle tissue and nervous tissue later in our course in different videos.

But for now, this concludes this example and I'll see you all in our next video.

During a dissection, a student comes across a tissue they don't recognize. They note it makes the internal structure of the spleen (an organ of the immune system that filters blood) and when they examine a section under the microscope, they see long dark branched structures, small circular cells, and a significant amount of ECM. What type of tissue could this be?

• A. Nervous Tissue.
• B. Muscle Tissue.
• C. Epithelial Tissue.
• D. Connective Tissue.

Both epithelial and connective tissue are involved in transport of materials in the body. How do their functions differ?

• A. Epithelial tissue provides a mechanism of transport while connective tissue regulates transport. 
• B. Epithelial tissue facilitates diffusion while connective tissue uses active transport. 
• C. Epithelial tissue regulates transport while connective tissue provides a mechanism for transport. 
• D. Epithelial tissue transports nutrients while connective tissue transports hormones.

Here’s what students ask on this topic:

What are the main functions of connective tissue in the human body?

Connective tissue serves several essential functions in the human body. These include:

• Protection: Bones, such as the skull, protect delicate organs like the brain.
• Transportation: Blood, a type of connective tissue, transports oxygen, nutrients, and waste products throughout the body.
• Binding and Support: Tendons and ligaments connect muscles to bones and bones to other bones, respectively.
• Insulation: Adipose tissue (fat) helps insulate the body and maintain temperature.
• Storage: Fat cells store energy, and bones store minerals like calcium and phosphate.

These diverse functions highlight the critical role of connective tissue in maintaining homeostasis and overall body function.

What are the common features of all connective tissues?

All connective tissues share two common features:

• Origin from Embryonic Mesenchyme: All connective tissues are derived from embryonic mesenchyme, a type of early connective tissue.
• Prominent Extracellular Matrix (ECM): The cells in connective tissue occupy less space than the ECM, which is composed of ground substance and protein fibers. This ECM can vary in consistency from liquid (as in blood) to solid (as in bone).

These features distinguish connective tissue from other tissue types, such as epithelial tissue, which has tightly packed cells with minimal ECM.

How does the structure of connective tissue relate to its function?

The structure of connective tissue is closely related to its function. The extracellular matrix (ECM), composed of ground substance and protein fibers, plays a crucial role. For example:

• Bone: The ECM is rock-hard, providing structural support and protection.
• Blood: The ECM is liquid, allowing for the transportation of nutrients, gases, and waste products.
• Cartilage: The ECM is flexible yet strong, providing support and cushioning in joints.
• Adipose Tissue: The ECM stores fat, which insulates the body and stores energy.

The diversity in ECM composition allows connective tissue to perform a wide range of functions essential for body maintenance and homeostasis.

What are the different types of cells found in connective tissue?

Connective tissue contains various cell types, primarily categorized into blast cells and site cells:

• Blast Cells: These are immature, active cells that build and secrete the components of the ECM. Examples include fibroblasts (in connective tissue proper), osteoblasts (in bone), and chondroblasts (in cartilage).
• Site Cells: These are mature cells responsible for maintaining the ECM. Examples include fibrocytes (in connective tissue proper), osteocytes (in bone), and chondrocytes (in cartilage).

Blast cells can revert to their active state for significant repair or growth, while site cells handle routine maintenance and minor repairs.

How does connective tissue differ from epithelial tissue?

Connective tissue and epithelial tissue differ in several key ways:

• Cell Arrangement: Epithelial cells are tightly packed with minimal ECM, while connective tissue cells are spaced out with a prominent ECM.
• Functions: Epithelial tissue primarily regulates transport and provides protection and sensation. In contrast, connective tissue offers structural support, transportation, insulation, and storage.
• Vascularity: Epithelial tissue is avascular (lacks blood vessels), relying on underlying connective tissue for nutrients. Connective tissue can be vascular, containing blood vessels.

These differences highlight the unique roles each tissue type plays in the body.