Buccal Smear Lab
The cells which line the inside of your cheeks are classified as a stratified squamous epitheliumtissue and are the surface of a mucous membrane. These flat, scale-like buccal cells (pronounced “buckle”) are shed constantly as the tissue is renewed. By gently scraping the inside of your cheek, these cells can be harvested, and when smeared and stained, may be used to illustrate a number of important biological phenomena including cell and tissue structure, oral bacterial floraand morphology, etc. This tissue is non-keratinized and therefore the surfacecells are living and still possess their nuclei, in contrast with shed epidermalcells. See DiFiore’s Atlas of Histology, 9th Ed, pp 326&327 for similar tissue found lining the vagina. (Note that the keratinized surfacecells of the epidermis have no nucleus.) Here is a labeled image of a buccal smear stained with methylene blue.
Compare the following steps with those in the Bact. Smear and Staining Protocol.
Equipment and Supplies
Soap and Water
Dropper Bottle of dH2O
Dropper Bottle of 0.3% Methylene Blue
Bunsen Burner or Alcohol Lamp, Striker
Bibulous Paper or Paper Towel
Preparation of Slide and Fingernail:
Clean a microscope slide well with soap & water, dry with a non-linty paper towel.
Cleanse very thoroughly under the nail of your index finger.
Place a small drop of dH 20 in the center of the very clean slide.
Harvest the Cells, Prepare the Smear:
GENTLY scrap the inside ofyour cheek to pick up some of the shed stratifiedsquamous cells. Do NOT scrape chunks. A toothpick may be used if you have no fingernails. Gentle scraping is the watchword, there should be no discomfort.
Express the material from under your nail by pressing with your thumb, and press the material into the drop of water on the slide, mix and spread the material around to the size of a dime.
Fix the Smear
Pass the slide through the flame several times to fix the smear. Do NOT heat the slide above a temp which is comfortable. You are merely “gluing” the smear to the slide.
Stain the Smear
Place a drop of 0.3% methylene blue on the specimen. Let sit for 1 minute.
Rinse off the excess stain with tap water. (Do not splash on your white shirt!)
Blot dry with an non-linty paper towel or bibulous paper. Do not rub.
Flame again briefly to dry slide.
Examine Under Microscope
Examine first with the 4x objective, scanning the entire field to find a well-distributed region. Avoidregions where cells may be piled up to thickly . Then view with the 10x and 40x objectives, illustrating the view at both powers. Note 1) the nucleus, 2) nucleolus, 3) cell boundary and 4) the variety of bacteria colonizing the surface of the cells.
For Microbiology only: you will be instructed on oil immersion use , then illustrate bacterial morphologies with the 100x oil immersion objective.
When finished, scrub the slide well in hot soapy water, rinse well and drain dry in a plastic test tube holder.