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Overview on how to examine and explore histology slides using a light microscope.
Hey everyone! This is Nicole from Kenhub, and in this tutorial, I’ll be giving you a few tips to help you correctly examine your histology slides.
As part of your anatomy studies, you’ll have to take histology classes that are geared to help familiarize you with the structures you are studying on a microscopic or cellular level. Oftentimes, at microscopic preparations or histology slides, students make mistakes when identifying structures or orienting themselves on the slide. It can seem very unclear and overwhelming. This is understandable because most students are used to looking at macroscopic structures like the arteries of the head and neck that we see here, and are not used to looking at microscopic ones.
This slide showing blood does not resemble the macroscopic anatomy at all, so it can be a bit confusing. There are also many different staining techniques that are used on preparations which change the contrast of the slide and add to confusion amongst students. Well, the good news is that we, at Kenhub, have put together a few tips to help you examine histology slides with more efficacy.
So, let’s begin with the first step.
Before you put your slide under the microscope, use the naked eye to determine the shape of your preparation. This might seem a little trivial, but looking at the slide before you put it under the microscope will help you orient yourself when you do eventually look at the slide under the scope. For example, in this cross-section, an annular or ring-shaped preparation can be seen. If you noticed before using the microscope, you’re one step closer to recognizing structures on the preparation.
Next, go ahead and place your slide under the microscope and calibrate the microscope so that your image is in focus and not fuzzy. Start at the lowest magnification and move the slide around to see the entire surface, since the slide is always bigger than the lens. Once you’ve had a look at the entire slide at the lowest magnification, go ahead and look at the slide using a higher magnification by stepping up to the next level being sure to bring the image into focus each time. You can do this several times to see higher and higher magnification of the slide as we’re doing here with our slide.
It’s important to make the image clear at each magnification in order to control which part of the slide you’re looking at especially if you want to zoom into a specific area. It’s also important to look at your slide at different magnifications because there can be some major and minor structures or cells that may not be visible at just one magnification. This is as far as we’ll zoom in in this example.
Once you’ve had a chance to look at your slide and the structures on your preparation at different magnifications, the next step is to write a description of the major and minor structures that you can see. Write down the name of the structures that you know and also write down the description of the ones you don’t know or aren’t sure of so you can ask your teacher or look them up later on.
Let’s do that for this slide. We can see blood vessels here, epithelial cells that appear to be pseudostratified columnar cells, lighter cells within that layer, connective tissue in this area containing collagen fibers which are stained blue, some empty space where there is no tissue, and hyaline cartilage if we move the slide.
After you’ve made notes of the structures you’re able to see and/or identify on your slide, the next thing to do is to determine the type of staining, sectioning, and preparation process used to prepare your slide. Let’s look at some different staining and preparation techniques to see if any match our slide.
Here, we are scrolling through a few examples of different stains including hematoxylin and eosin, Periodic Acid Schiff reaction, silver impregnation, toluidine blue, osmium tetroxide, and Masson’s trichrome. As you can see, this Masson’s trichrome staining technique looks very similar to the slide we’ve been examining. Our slide also has a trichrome stain as is a Ladewig’s trichrome which is commonly used to see muscle and collagen and differentiate connective tissue from other cell structures.
Okay, now that we’ve looked at the slide under the microscope and identify the structures and staining techniques used, it’s time to put all of these information together and identify the preparation. If we put together all the structures that we see, what part of the body would make the most sense for the slide? Looking at the trichrome staining, it’s easy to see connective tissue, blood vessels, epithelial cells, and hyaline cartilage, which we located here.
Hyaline cartilage is found in a limited number of places in the body including in the ears under the skin, in the nose attached to the nasal septum, in the trachea and smaller respiratory tubes in the form of structural rings, in the structure of the irregularly-shaped larynx, and the smooth articular surfaces of bones in synovial joints. If we remember the general shape of the preparation on the slide, we can see the overall ring shape.
Any ideas yet? The shape of the preparation gives us a clue and eliminates the possibility of the slide being a sample of nose or ear cartilage as well as the articular surface of bone. It probably isn’t the larynx as well since that is so irregularly-shaped. The trachea and smaller respiratory tubes have a distinct ring-shape as well as hyaline cartilage. There are also blood vessels running through the slide which we see here and we can see the uneven edge of epithelial cells against an opening or lumen and the thick layers of connective tissue deep to that.
We also saw lighter-stained cells within the pseudostratified columnar epithelium. These are goblet cells which secrete mucus and the light purple area in the lower portion of the slide just here is more likely a mucosal lining. This should be a big clue. Have you discovered what this preparation is? The trachea!
The trachea is ring-shaped, has hyaline cartilage as well as many blood vessels, and a thick lining of epithelial cells and mucosa. Smaller respiratory tubes like the ones beginning to branch off here are much thinner and would look different on a slide and the pseudostratified columnar epithelial cells transition to cuboidal cells as the tubules get smaller.
Congratulations! You’ve identified a preparation. You’re not done yet, though. It’s a good idea to add additional information to your notes after identifying the preparation. These can be cell functions, cell functions of that anatomy, and additional information from your lectures and teachers. Here we are noting the function of the trachea, the cartilage rings, and the mucus-secreting epithelial cells. This helps you to really understand why the histology of a section looks the way that it does.
Remember, form follows function, even at the microscopic level.
So that’s it! You’re all done with your examination of your histology slide. Hopefully, you’ll have a much easier time examining histology slides, but remember, try not to jump to conclusions when examining your slides even if you think you already know what preparation you’re looking at. Keep an open mind and review all the content at your disposal before definitively identifying your slide.
That’s the end of the tutorial. Thanks for watching and happy studying!