Epithelial Tissue

Epithelial Tissues are found all over the body. They mostly cover body surfaces, organs, and the inner lining of body cavities. These cells divide very often, causing injuries to heal quickly.  Epithelial cells are all tightly packed so they are protected very well. Epithelial Tissues are divided into many different classifications including, squamous, cubiodal and columnar. They are also divided between simple and stratified. These tissues, however, do not have blood vessels. On the other hand, connective tissues which are under these epithelial tissues do have blood vessels.

One type of Epithelial is squamous. These cells are flattened and make a smooth surface usually used for forming the walls of capillaries and membranes. To me they remind me of a smooth tile surface that lines the walls of a house or the floor. However, since the squamous cells are so thin they can be damaged or destroyed fairly easily. From this picture you can see the shape of the squamous cells.

You can see that they are thin and smooth, like the tile surface I explained earlier. It would make sense from seeing this picture that these cells would form as a wall inside the body.

The next type of cell is the Cuboidal cells. Just saying the name of the cell can help you determine what this cell looks like. These cells are simple cube shaped cells that help with secretion and absorption of a material. In the middle is usually a large spherical nucleus.  You can usually find these cells in the kidney tubules and in the small portions of small glands.
This photo shows the shape of these unique cells. From the picture you can see that the cells are indeed cube like and have a large circle nucleus.

Columnar is the next type of cell and its name also helps reveal the shape of the cell. Columnar cells are tall cells that almost look like large columns; also the nuclei in the columnar cells are oval shaped. Some of these cells have cilia which are constantly moving. The cilia help in situations like for females moving the egg cell through the uterine tube to the uterus.

This picture shows that the long columnar cells. These cells look like large tall columns and on top of the cells, are the hair looking cilia.  The main purpose of the columnar is to absorb nutrients from digested food.

The next Epithelium is the Transitional Epithelium.   Transitional epithelium is used to change in response to increased tension. It is found in the inner ling of the urinary bladder and in the ureters. When the wall of one the organs reduces in size or contracts the tissue is usually made up of layers of cuboidal cells. Pseudo stratified Columnar is a single layer of cells that are all at different heights. Many of these cells do not even reach the free surface.  The nuclei are never in the same place they are always seen in different layers. These cells main purpose is for the secretion of mucus.

This is an example of Pseudo stratified columnar. As you can see the nuclei are in different layers.

All of these cells are split into another two division being simple and stratified.  Simple is defined usually by only a single layer of cells while as stratified cells usually have several layers of cells. Stratified cells are usually not as common as simple Epithelia cells, but they are equally as important.

The photo above shows a stratified squamous epithelia cells. As you can see there are a several layers of cells all piled up onto each other.