Connective tissue is found throughout our body. There are many types of connective tissues depending on what it has to do. For example:
In order to understand connective tissue, you must understand its general properties, the extracellular matrix material in which it lies as well as the cell types it contains. You can follow the links in the last sentence, or just keep reading, in order to spend more times on these concepts. If you understand them already, jump down below those sections to read more about some of the specific types of connective tissue.
Click here to link to another website that describes connective tissue... it is a beautiful site with lots of images (clicking on an "E" button will show you an Electronmicrograph while clicking on a "L" button will show you a Light micrograph). Just keep in mind that it goes into even more detail than I require, OK?
It is difficult to describe general properties of CT in the same way as I did for epithelial tissue. That's because CT is so much more diverse. So, keep in mind that some of the characteristics that I am writing may not fit all of the CT types perfectly-- but they will fit most of them.
The space between cells can be called the extracellular space/material or the intercellular space/material. "Extra-" means outside of, while "inter-" means between. I prefer to use the term extracellular space to prevent other confusion... that's because intercellular is easily confused with another term we will be using: intracellular. "Intra-" means within, and we will use intracellular to discuss what is inside the cell.
In the drawing to the right, the extracellular space is all in pink. This space is not a vacuum, but it is filled with material. If the material is only liquid, the tissue as a whole will be loose. An example of that is in blood. If the material in the extracellular space has some tough strands (called fibers) of protein in it, that gives the entire tissue a stronger consistency (because the cells are now sitting in a mesh of fibers).
This diagram shows a connective tissue with a lot of extracellular space. There are some connective tissues with less (and even more) extracellular space. If there's a lot of extracellular space (with little material in it), the tissue could be quite loose, while if there is little extracellular space the material will tend to hold together well.
You should now understand that it is important to know how much and of what consistency the extracellular material is for any one type of connective tissue. Please note that I will refer to it from now on as extracellular matrix material, or even just as matrix, because it is a complicated enough material to be called a matrix.
Extracellular Matrix Fibers:
There are three main cell types in connective tissue. These three cell types may appear in most of the types of connective tissue. There are also cell types that are specific for certain connective tissues (and are only found there).
The three main cell types are:
Other cells that you may find in specific connective tissues are:
If a connective tissue has plenty of cells within it, it is better at recovering after injury. For example, if the skin is cut, and the dermis is thus cut, the mast cells will, of course, help get blood in the area to fill the hole left by the cut and then will also get the blood to begin clotting. After that, however, we need to replace the clot with more dermis. This is possible because the fibroblasts in the remaining dermis begin dividing and secreting more fibers for the matrix. As the fibroblasts make more dermal connective tissue, the macrophages start removing the clot. And, voila! The repair is done.
If, however, a connective tissue has few cells (and/or blood supply is limited), it is more difficult to repair that connective tissue. An example of this is in tendons and ligaments. You probably also have heard that it is difficult to repair tendons and ligaments after injury-- the healing time is much longer than for a broken bone.
Not all of the types are
discussed here, since we are also doing them in lab.
© 2011 STCC Foundation Press