Anatomy 101: A guide to help pass anatomy and physicology practical : epithelial tissue: simple squamous

Learning Anatomy 101: Epithelial Tissue.

If you are seeking help in passing anatomy 101 you have come to the right place. Whether you are taking anatomy 101 as a nursing student, biology major or part of pre med studies, understanding the human anatomy is important if you wish to pass anatomy 101 and to continue your studies.

Most anatomy 101 classes require you to complete a lab portion of the class. The anatomy lab will be an opportunity for you to learn the anatomy of the human body by seeing and feeling structures of the body. You will be on your knowledge of anatomy through a test called a practical. This series of tutorials is meant to help you pass the anatomy practical. It serves as an anatomy guide to make learning anatomy easier.

Relax and take a few deep breaths. You are going to do great!

Is it tissue?

As I explained in the first part of this series, it is important to have a system to determine quickly what you are looking for. If you are sure that the station you are at is presenting a tissue, you should narrow your choices down before even looking into the slide.

Tissue = Tigers which Can Eat Many Natives

Can= Connective

Eat= Epithelial

Many= Muscle

Natives= Nerves

Look at the station, then the question

Once giving the station a broad inspection and after using TOMB, you should read the question. Often the question will lead you very closely to the answer:

What Tissue is this
What Structure is the pointer pointing to
Where can this be found
What is the Function of this tissue

Look for clues in the question.

Notice how it doesn't take up the whole slide?

This connective tissue takes up the whole view

Apical surface ( Red) Basal surface ( Black)

Layers from the side ( Black) and the top of one layer ( Red)

Looking at the top of one layer of epithelium

Identifying Epithelium

When you first look through the microscope or at a picture, notice where the pointer is. Often epithelium has to be pointed out because it doesn't take up the whole visible area of a slide.

Muscle, Bone and most connective tissues will fill your eyepiece.

Epithelial tissue must have an open surface. Think of a diaper. A diaper has a lining in it so that when the baby uses the diaper some things can get absorbed into the deeper layers. The layer that is against the skin is the free surface or the Apical surface. The deepest part that is fixed to the outside of the diaper is the Basal surface.

An A has a sharp point at the top which reaches high, Apex is the top, A is before B, the Apical surface is the free surface. B is for basal which sounds like Base and it lies on the base of that particular tissue.

There will always be an open space which the Apical surface is pointing towards EXCEPT if you are looking down on the tissue.

Think of a roll of toilet tissue. If you look at it from the end you will see the layers of paper wrapped around a cardboard core but if you look at it from the side you will just see the top of one layer.

Recap: If the image looks the same though the whole view and takes up the whole image, rule out epithelium EXCEPT if all of the cells fit together in which case you may be looking down on one layer.

So you are sure it is epithelium

As I stated earlier, epithelium will sometimes be mixed in with other tissues so look for a pointer.

Once you are confident that it is epithelial tissue, which kind is it?

Simple
Stratified
Transitional
Pseudostratified

Simple and Stratified.

Simple means one layer. Stratified means many.

There are three types of cells associated with simple and stratified epithelium:

Squamous: Flat-Squashed
Cuboidal-like a cube
Columnar -like a column

Look for the layers, then look for the nuclei. If the nuclei is close to the edges of the cell and they appear flat, it is squamous.If the nuclei sits in the center of the cell like #1 on a die it is cuboidal.If the nuclei is towards the bottom of a long cell, think columnar,

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Squamous

Squamous epithelium is flat and may be in layers. As with any tissue, the magnification is going to affect what the tissue looks like as well as the way the tissue was sliced. Simple ( one layer) squamous will either be seen as a sheet (a) , as a cross section from a lower magnification (b) or a cross section from closer (b)

A: Remember the cells have to have a free (Apical) surface which in this case is pointing up at you.

B: This isn't as magnified as A but we see the nuclei in single rows. There isn't much dye in the center of the circle, so it is air. This is aveoli in the lungs.

The Pictures above are classic examples of simple epithelium. When you look at the first one you should be thinking:

I can see a nuclei in the center, which could be cuboidal, but there is no apical surface so I must be looking down on to simple squamous epithelium.

When you see the 2nd, you should notice that white means no stain was taken up in the slide, so it must be air. These are circles of air, lined by something. We breath in air and we absorb it through our lungs. The lining must be thin in order to exchange gas so it must be simple squamous.