Observing human cheek cells under a microscope offers a clear and accessible introduction to cellular biology. These cells, formally known as buccal epithelial cells, are constantly shed from the inner lining of the mouth, making them easy to collect. This simple procedure allows for direct visualization of animal cell structures, providing an engaging and educational experience for anyone curious about the microscopic world. It is a common and fascinating first biological experiment due to its simplicity and the readily available sample.
Essential Supplies
To begin observing cheek cells, gather a few basic items. A compound microscope is necessary for magnification, allowing you to see the tiny cellular details. You will also need clean glass microscope slides and coverslips, which are thin pieces of glass that protect the sample and the microscope lens. Cotton swabs or clean toothpicks are used to collect the cheek cells from your mouth.
A staining solution, such as methylene blue, adds color to the otherwise transparent cells, making their structures more visible under the microscope. Methylene blue specifically stains the nucleus, a prominent part of the cell. Distilled water is also needed for preparing the slide, and a dropper helps in precisely applying liquids. Paper towels are useful for blotting excess liquid.
Collecting and Staining Your Cells
Gently scrape the inside of your cheek with a clean cotton swab or the non-sharp end of a toothpick; you do not need to press hard. This collects buccal epithelial cells, which are flat cells with a round nucleus. After collection, carefully smear the swab or toothpick onto the center of a clean microscope slide. This transfers the cells onto the glass surface.
Next, add a small drop of distilled water onto the smeared cells to create a wet mount. Then, place a single drop of methylene blue staining solution onto the water droplet containing the cells. Methylene blue highlights the nucleus. Gently lower a coverslip over the stained sample at an angle to avoid trapping air bubbles, which can obstruct your view. Finally, use a paper towel to absorb any excess liquid from the edges of the coverslip, ensuring the sample remains flat and stable.
Microscope Operation and Observation
With your slide prepared, place it onto the stage of the microscope and secure it with the stage clips. Begin with the lowest magnification objective lens, typically 4x or 10x, to get an initial broad view of the slide. Adjust the coarse focus knob to bring the image into general focus, then use the fine focus knob for sharper clarity. You may need to adjust the light intensity using the microscope’s diaphragm or illuminator to achieve optimal brightness.
Once you locate cells under low power, rotate the revolving nosepiece to a higher magnification, such as 40x. Refocus using only the fine focus knob at higher powers to avoid damaging the slide or objective lens. At higher magnifications, you can observe individual cheek cells, which typically appear as irregularly shaped, flattened structures. Look for the distinct cell membrane, the outer boundary of the cell, and the cytoplasm, the jelly-like substance filling the cell. The most prominent feature will be the darkly stained, often circular or oval nucleus, located near the center of the cell.
Safety and Cleanup
Avoid ingesting the methylene blue stain, as it can be toxic if consumed and may cause irritation upon contact with skin or eyes. Handle glass slides and coverslips carefully to prevent breakage and cuts.
After observation, proper cleanup ensures the longevity of your equipment and prevents contamination. Remove the slide from the microscope stage. Dispose of the used cotton swab or toothpick appropriately. The microscope slide and coverslip can be cleaned by soaking them in warm, soapy water, then gently scrubbing with gauze or a soft brush, and rinsing thoroughly with distilled water. Allow them to air dry or gently blot them with a lint-free cloth before storing them properly.