That of Epithelial Tissues (feat. Human Bodies)

     A tissue is a group of cells with similar functions; one tissue type is Epithelial. An epithelial tissue is composed almost entirely of cells and can form sheets held together by junctions. Epithelial tissue is regenerative, meaning it rapidly replaces loss of cells through cell division. This tissue can be classified firstly as simple or stratified. Once that has been decided, the cell will be named squamous, cuboidal or columnar according to it's layers, shapes and placement of nuclei. Just to make it harder, there is a category, pseudostratified, that can occasionally take place of simple or stratified.

     A simple epithelial cell will have a single layer whereas stratified will have multiple layers. Squamous will have disc shaped nuclei and be thin and flat. Cuboidal will have a single layer of cube-like cells with circular nuclei. Columnar has tall cells with round and oval nuclei. When these are stratified, they will be stacks and layers of the shaped cells; when psuedostratified, the cells will have nuclei in a matter of all different places. Psuedostratified Columnar will have different lengths of columns with nuclei in many different places (it is the least likely to be found). To make this more complicated, there is a property called 'transitional', which means that at the top layer, nuclei will be uniform but as they go down the layers, they begin to get 'messy' and are placed randomly.

Now that the science part is over, we can get on to the fun!

     Thanks Bill Nye for that smooth transition. During class, we were divided into two groups to do a photo based activity. We were instructed to use our actual entire bodies to form the cells...... With our bodies. So we gave it our best shot and hopefully the Caption Crew can assist in informing you throughout the Photo Journey. 

Simple Squamous - Single layer of flat cells, disc nuclei and scarce cytoplasm. (This cell provides a friction reducing liner that allows for diffusion.)

Stratified Squamous- Consisting of a thick membrane (no offense girls) made of many cell layers. (This cell protects things underneath it that have frequent abrasion.)

Simple Columnar- Single layer of tall column like cells. This cell will sometimes have cillia, which allows it to absorb and secrete accordingly. The non-cilliated form of this tissue can be found in the gallbladder and digestive tract.

Transitional- Several Cell layers, the top being dome shaped. This cell allows the tissue to stretch, which is a useful property in the bladder and uterus... which is where these tissues can be found.

Simple Cuboidal- single layer of cube shaped cells that have large spherical nuclei. This cell also has the ability to secrete and absorbe and can be found in the kidney tubules and in the lining covering the ovaries.

Stratified Columnar- usually two cell layers that are pretty thick, but they are rarely found in the body. They can occur in transition areas between other types of epithelia.

Pseudo-Stratified Columnar- single cell layer at different heights with the nuclei scattered randomly, instead of uniformly throughout the columns. This cell also secretes but it also propels mucus (ew) and are present in the male sperm carrying ducts.

     Thus concludes our cellular lesson using the ever-so-kind members of my classroom. Until next time......