Biology 1110 Laboratory Laboratory # 3 Beginning Histology Epithelial Tissue Support/Review Materials All of the micrographs in this presentation were photographed in the MnWest Biology laboratory unless otherwise noted. The microscope symbol that you see indicates a change in microscope power. A left mouse click on the microscope most often increases the viewing magnification. Give it a try.

Epithelial tissue. This tissue forms coverings and linings and makes up the ducts and secretory cells of numerous glands and certain organs.

 1. Squame or squamous cells - these have an irregular shape and flat profile.  2. Columnar cells – these cells are somewhat column-shaped. Their height is much greater than their width or depth.  3. Cuboidal cells – these cells are shaped somewhat like cubes. Their height, width, and depth are about the same.

 1. Simple.  Simple epithelium consists of a single layer of epithelial cells resting on a basement membrane. Most epithelial tissues are simple.  2. Stratified.  Stratified epithelium consists of multiple layers of cells.

 Simple Epithelium Stratified Epithelium  1. Simple squamous 1. Stratified squamous  epithelium epithelium.  2. Simple columnar  epithelium  3. Simple ciliated  epithelium  4. Simple cuboidal  eithelium 

 Tissue characteristics – this tissue is composed of a single layer of thin, irregular shaped squame cells. Wherever you find this, you will find a thin, moist membrane.  The next slide provides you with a high power view of two stained samples of simple squamous epithelium and identifies a number of animal body locations.

Simple Squamous Epithelium Location examples Peritoneum – the lining of the body cavity. Mesentary – a double layer of simple squamous epithelium that invests and supports certain abdominal organs. Endothelium – the smooth lining of the blood vessels. Endocardium – the lining of the heart chambers.

 Tissue characteristics – The above name tells you that this tissue is made up of a single layer of column-shaped cells. This single layer of cells sit upon the basement membrane, which in turn connects the epithelial tissue to the underlying tissues. This tissue lines much of the gastrointestinal tract.  The next slides contain samples of this tissue demonstrated at both low and high power. A model is also used in the demonstration, and helps us in locating this tissue in the animal body.

Simple Columnar Epithelium The model to the right demonstrates the entire wall of the small intestine. The finger-like projections are called villi. A tremendous number of these greatly increase the working surface of the small intestine. The outer surface of the villi is simple columnar epithelium.

Simple Columnar Epithelium The low power micrograph demonstrates a number of intestinal villi. Note that the simple columnar epithelium is stained and quite easy to recognize. Let’s take a look on high power.

Simple Columnar Epithelium On high power we can clearly see the columnar epithelial tissue. One of the columnar cells has been outlined. The nucleus in each cell is deeply stained (red) and easily observable. Observe also, the mucus-producing Goblet cell.

Simple Columnar Epithelium Another low power view of columnar epithelium. Note the convoluted (wavy) nature of this tissue. Let’s look again on high power.

Simple Columnar Epithelium The column-shaped cells of this simple epithelium are quite obvious. Again, a column- shaped cell has been roughly outlined.

Tissue characteristics - This is also a simple (single- layered) epithelium. There are a couple of types with all columnar cells containing many bristle-like cilia on their apical (outside) surface. The cilia sweep in a coordinated fashion in order to move material along the tissue surface. Each cilium is tiny. There may be up to 100 cilia per epithelial cell.

Ciliated Columnar Epithelium This low power micrograph demonstrates a type of ciliated columnar epithelium. This tissue sample is taken from the respiratory tract, and is called pseudostratified ciliated columnar epithelium. Take a closer look.

Ciliated Columnar Epithelium The distribution of nuclei give this simple epithelium a stratified (layered) look. The cilia (at the pointer) sweep in a coordinated fashion to move mucus and foreign material in an upward direction. This respiratory cleansing mechanism is called the mucociliary escalator – cool name!

Ciliated Columnar Epithelium This micrograph also provides us with a low power view of ciliated epithelium. Note the cilia at the pointer tip. Take a look on high power

Ciliated Columnar Epithelium The many cilia extending from these columnar cells are very obvious. Where in the human (and in other animals) can this tissue be found? 1. Lining much of the respiratory tract. 2. In females, this also is found lining much of the oviduct (uterine tube), where it helps to transport the egg or developing embryo towards the uterus.

 Tissue characteristics – This tissue consists of a single layer of cube-shaped cells. This tissue is found forming the ducts and channels in certain organs. These cells are also the secretory cells in numerous glands.

Simple Cuboidal Epithelium As the name of this tissue indicates, it is made of a single layer of cube-shaped cells. Note the cuboidal cells at the pointer. These cells are forming a duct or tubule of some sort. Let’s take a closer look.

Simple Cuboidal Epithelium Cuboidal epithelium is found in numerous locations in the animal body. It is found throughout the kidney and helps to form the kidney tubules. In many glands, cuboidal epithelial cells are the cells that produce the glands secretory product. A good glandular location example would be the thyroid. Check it out.

Cuboidal cells of the thyroid gland A number of thyroid follicles are clearly visible in this micrograph. Cuboidal epithelial cells form these follicles and are involved in the production of the thyroid hormones. The stained nuclei of these cells are clearly visible. The boundary of one cell has been enhanced to demostrate the cube shape.

 Tissue characteristics – the name of this tissue tells us that it consists of numerous layers (strata). Being quite protective, this tissue is found where there is the potential for wear and tear.  Tissue location – the outer skin is made up of this tissue where it protects and waterproofs the animal. The tissue is also found lining openings into the body, such as the oral cavity and others.

Stratified Squamous Epithelium Note the many layers (strata) of cells and how the cells change as they migrate towards the surface. The many layers of this tissue provide great protection. Location examples: - the outer body covering(skin) -lining of your oral cavity. -lining other openings into the body. Look on high power

Stratified Squamous Epithelium You will find this type of tissue covering surfaces where wear and tear is a possibility. Your outer body surface (outer skin) and the lining of your oral cavity are two good location examples. The outer skin cells are dead and keratinized forming a tough, waterproof covering. The outer cells of your other stratified epithelial tissues are living cells.

 The surface cells continually slough off and need to be replaced.  Rapid cell division in the lower layers (germinal layers) produce the replacement cells that begin their migration towards the surface.

Note the stratified epithelium in the micrograph to the right. This is like the tissue that lines your oral cavity. If you would lightly scrape this lining you could easily collect living cells from the outer layer for examination. Go ahead – push the button  The cells you just collected and stained are the irregular-shaped squame cells.

The End

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