Histology can be a fascinating study with essential use cases in the medical field. Preparing histology slides to study can be tricky and requires correct preparation for accurate and consistent results. When created with the right tools and equipment, histology slides can aid scientific studies and diagnose diseases such as cancer.
What Are Histology Slides?
Medical histology is the study of tissues, cells and organs under a microscope. To prepare a tissue sample for viewing, it must go through fixation, embedding, sectioning and staining. This process allows you to clearly view the anatomy, structure and role of the tissue and any changes it may have undergone. Histology plays a crucial role in biological research as it aids in understanding the human body and how it functions on a microscopic level. With this understanding, you can diagnose diseases, conduct autopsies and even aid in forensic investigations.
There are four main types of human tissue that you can examine using histology slides:
- Epithelial tissue is a layer of connected cells that line the outer surface of the human body and internal organs and blood vessels.
- Connective tissue cells live within an extracellular matrix that supports, connects and protects tissue and organs. This includes blood, bone and cartilage.
- Muscle tissue contains muscle cells that can contract to allow movement.
- Nervous tissue contains nerve cells that carry out rapid communication within the body.
Necessary Equipment for Histology Slide Preparation
Throughout histology slide preparation, many pieces of equipment are needed to ensure precise, accurate results. Microtomes, slide stainers, mounting mediums and coverslips are just a few of these.
A microtome is an important piece of equipment within the histology preparation process as it is used to slice tissue samples into thin sections. You can then mount these sections onto a slide and view them under a microscope. There are numerous types of microtomes and choosing one is dependent on your tissue sample and how you prepared it.
A rotary microtome is the most common, as it has a standard blade that can cut through most tissue. However, if your tissue is fatty or consists of bone, you'll need to use a vibrating or saw microtome, respectively. If you need thin samples for a transmission electron microscope (TEM), you'll need an ultramicrotome to slice thinner sections than a normal microtome produces. If you have a frozen sample, a cryostat microtome will thinly slice your specimen within a cryogenic chamber, which will keep it frozen.
Staining is the process used to color tissue samples so that you can view them better under a microscope. While you can do this manually, staining machines can provide consistent, high-quality results. These machines can also improve efficiency as they can usually hold and stain many samples at once. You will also need to purchase the specific type of stain depending on what you will be examining in your tissue sample.
Mounting Media and Coverslips
Once you have prepared and stained your tissue sample, you'll need to place it on a histology slide under a coverslip using a mounting medium. The two main types of mounting mediums are water-based and organic solvent-based. Choosing the right medium can help preserve and keep your specimen from drying out. Selecting the correct type and thickness of coverslip is also essential depending on your sample and how you'll examine it.
How to Prepare Histology Slides
Taking the time to prepare a histology slide correctly is necessary as the correct protocols prevent tissue putrefaction and autolysis and allow observation of the tissue as close to its living state as possible. You can follow these steps to prepare a histology slide correctly.
1. Specimen Preparation
You can only observe a tissue sample under a microscope once you complete the following process:
- Fixation: A chemical fixative or freeze-drying method is used to preserve and harden the tissue so it doesn't degrade.
- Embedding: The stabilized tissue sample is placed inside a more solid medium, such as paraffin wax.
- Sectioning: A microtome cuts the tissue into incredibly thin slices that can be viewed under a microscope.
- Staining: The sliced tissue is stained to create visual contrast between the various components of the tissue sample.
2. Staining Techniques
As most cells are transparent or the same color, staining your tissue sample will help you examine your histology slides under a microscope. It does this by changing the color of particular cell components, which provides contrast and differentiates the cells from one another.
Scientists generally use a combination of Hematoxylin and Eosin (H&E) to stain tissue samples. Hematoxylin is a basic stain that can be either purple or blue and bonds to basophilic structures like cell nuclei and ribosomes. Eosin is an acidic stain that dyes cells pink or red. It binds to acidophilic components, including cytoplasm, collagen and muscle filaments.
If you need to stain neutral components or cells that don't take to aqueous dyes, you'll need to use a specialty stain. There are specific stains that you can use depending on what you need to identify in your sample. For example, the Giesma stain is used on bone marrow and plasma cells, while the Periodic acid-Schiff (PAS) stain can highlight glycogen and mucus.
3. Coverslipping and Mounting
Once you've prepared a tissue section, you must mount it under a coverslip to examine it under a microscope. A coverslip will also allow you to store your sample for long periods.
Here are the standard ways you can mount samples on a histology slide:
- Dry mount: Place the specimen or tissue section directly on the slide and cover it with a coverslip.
- Wet mount: Place a drop of the mounting medium onto the slide, taking care to avoid bubbles, and gently lower the coverslip into place.
- Smear mount: Liquid specimens can be examined by smearing them onto the slide and allowing them to dry before covering them with a coverslip.
Buy Quality Used Histology Equipment From New Life Scientific
Using equipment in your histology procedures can increase the quality and reliability of your samples and results. On top of this, equipment can improve the efficiency of sample preparation. Your equipment needs to be well tested to determine its accuracy before you buy it, and it also needs to be adequately maintained to ensure consistent and reliable results.
However, histology equipment can often be too expensive for most people. This is where purchasing used equipment can be beneficial — you don't have to pay the full price! At New Life Scientific, we offer used histology equipment that our team has tested for quality assurance. We also provide fast response times to any queries and offer a 120-day warranty on any equipment you purchase from us.