Connective Tissues

In this lesson, we’re going to talk about connective tissues and their structure and function, and we’ll run quickly through a few types.

First, let’s look at some characteristics of connective tissues. If you haven’t watched the epithelial tissues lesson, make sure you do that because you’ll see that connective tissues are basically the opposite. Instead of cells being densely packed, they’re actually spread really far apart, which means there’s a lot of intercellular substance. Intercellular just means between the cells. The farther apart they are, the more stuff between them. They also have no free surfaces, that means that all surfaces of connective tissues are touching some other tissue. They are highly vascular meaning there are a lot of blood vessels running through them, as well as nerve endings. Now, similarly to epithelial tissues, they’re highly regenerative, which means the cells will be replaced frequently through the process of mitosis. One thing to know is that each type of connective tissue has specific types of cells – a specific type of matrix, which is the substance between the cells, and specific types of fibers suspended in that matrix. It might be elastic fibers in a weak gel matrix that allows some flexibility and movement or it could be more of a semi-solid matrix like we see in cartilage. In this lesson, we aren’t going to list all of these out for you, but we have attached a cheatsheet that has all of the cells, fibers, matrix, and functions of the main connective tissues, so make sure you check that out.

Now, each type of connective tissue has its own functions, which we’ll talk about in a second; but, let’s look at the overall functions of connective tissue. First – connective tissue… connects! It can connect, bind, or anchor two things to one another – maybe tissue to tissue or organ to organ or even organ to the wall of a cavity. Connective tissue also forms the structural tissue or stroma of many organs in the body – it’s what gives them their shape. We also see connective tissues playing a huge role in protection, both from mechanical trauma (like with adipose tissue, bone, and cartilage) and from infection because we find cells like macrophages and white blood cells inside some types of connective tissues. And finally, we see adipose tissue (otherwise known as fat) serving as insulation under the skin to help maintain our temperature.

So let’s just briefly hit on the main types of connective tissues and their functions. First is areolar or loose connective tissue. This is found in our subcutaneous tissue under the skin, it’s also found in the spaces between organs. It’s like the packing material of the body – it just kind of fills in all the spaces. We also see areolar connective tissue around muscles, glands, blood vessels, and nerves – serving to provide shape and support to those structures. We also see macrophages hanging out in areolar connective tissue, so it helps to provide some protection from bacteria as well.

Next is white fibrous connective tissue. You’ll hear this term a LOT when you get to the bone and muscle lessons. White fibrous connective tissue makes up our tendons, ligaments, and aponeuroses that connect muscle and bone – so which is which? Tendons connect muscle to bone – these are what help us actually move when the muscle contracts. Ligaments connect bone to bone and usually help to stabilize joints like the knee or ankle. And Aponeuroses actually connect muscle to muscle – the most common example of this is in the muscles of the skull that are connected to each other by this type of connective tissue. We also see white fibrous connective tissue in the fascia that covers muscles and organs, the sclera of the eye, and in any scar tissue that forms in our body.

Next is Yellow Fibrous, otherwise known as Elastic connective tissue. This should help you remember where it’s located. First is the ligaments between our vertebrae called the ligamentum flavum. Think about this – the ligaments in the knee serve to kind of hold it in one place so it doesn’t slip and slide and only moves the way we want it to, right? But here in the spine, we need to be able to twist and turn and bend and flex and move every which way, right? So we need these ligaments to be a little more elastic. We also see elastic connective tissue in our vocal cords to help with speech and in the walls of large arteries like the aorta and carotid arteries. The elasticity helps it to withstand the high blood pressure in those arteries.

Then we have reticular tissue – this helps form the stroma or structural shape of organs. We see this especially in the liver and lymphoid organs. Literally if you didn’t have the reticular tissue, you’d just have a bunch of cells and fluids and it would all fall apart.

Next is adipose tissue – otherwise known as fat. You may not want to think your fat is beneficial, but it really is. It helps store energy inside the cells, protect from trauma, and insulate us to prevent too much heat loss. It is also a major component of the omentums. The greater omentum covers the gut to protect it and the lesser omentum connects the liver to the stomach – basically to keep the stomach from falling to the bottom of the abdominal cavity!

Last connective tissue we’ll talk about is cartilage. Your outline has a LOT of information for you about cartilage, but I just want to hit on the main functions of each of the 3 types of cartilage. Hyaline cartilage is the most prevalent cartilage in the body – chances are if you just thought of a place where there’s cartilage – it’s hyaline cartilage. It provides structure and support and is found in places like our joints, between the ribs, and the tip of our nose. Fibrocartilage is much stronger than hyaline cartilage and it helps to serve as a shock absorber. So those places in our body that take the most weight or shock when we walk or jump. It’s found in the discs between the vertebrae, the menisci of the knees, and in the pubic symphysis. Last is elastic cartilage. Just like yellow elastic connective tissue, it provides more flexibility than the others. We see this kind of cartilage in our ears, (including the eustachian tubes, external ear and external auditory canal) and our epiglottis. Notice the E’s!

So let’s just recap what you need to know about connective tissues. Cells are spread apart with lots of intercellular substance, no free surface, and they are highly vascular. Connective tissues serve to connect, form structures, protect, and insulate. Each type has specific components – certain types of cells, fibers, and matrix – and they all have their own specialized functions. Again, check out the cheatsheet attached to this lesson to see more!

So, that’s it for connective tissues. Now, go out and be your best selves today. And, as always, happy nursing!