PRACTICAL 3: EPITHELIUMINTRODUCTIONThe epithelium or epithelial tissue, consists of sheets of cells that cover the external surfaces of the body, line the internal cavities, form various organs and glands, and line their ducts. The histology of the lining epithelium, however, differs from organ to organ, depending on its location and its function.

OBJECTIVES1) To understand examples, functions, and distinguishing features

of each type of epithelial tissue2) To associate structure with function for each type of epithelial

tissue

METHODOLOGYYou will need to pass up a permanent slide of your cheek cells (label before you pass up by the end of the practical) and to pass this practical (due in 7 days after this practical). You will answer all the questions in your results and discussion section.

EquipmentsSlide warmer/ heater, glass slide, coverslip, staining jars and racks, measuring cyclinder, balance, heater and stirrer, compound microscope, beakers, conical flasks, toothpicks, slides of epithelial tissues.

ChemicalsWright’s stain, phosphate buffer solution (pH 6.4), DPX/ Canada Balsam.

A. Making a wet mount1. Rinse your mouth with tap water before you start this experiment.2. Put a drop of distilled water on a microscope slide.3. Gently scrape the inside of your cheek with the tip of a clean

toothpick and stir the tip with the drop of water on the slide.4. Lay a coverslip over the preparation by holding the cover slip at a 45o angle to the drop of water and then slowly lowering the coverslip over the drop, forcing trapped air out of the preparation.5. Examine your cells under scanning, low and then high

magnification. NEVER VIEW A SLIDE WITHOUT A COVERSLIP.6. The cells may be clumped, so scan the slide to find cells that have

floated free.a) Can you clearly see the “living” cells without the use of stains or

dyes?7. Place a small drop of Wright’s stain at the edge of the coverslip.8. If the stain does not readily diffuse under the coverslip, pull the fluid

under by touching a dry paper towel to the opposite edge of the coverslip.

9. Now, draw and label the epithelium cells (under low and high magnification).a) What is the shape of your cheek cells?

Name: Matric No.:

b) Are nuclei visible in epithelial cells of your cheek?

B. Making a permanent slide1. Repeat steps 1-3 from A) Making a wet mount.2. Dry your slide on the slide warmer/ heater.3. Place 20 drops of Wright’s stain on the dried slide.4. Now place 20 drops of the phosphate buffer (pH 6.4) on the slide. Leave for 10 minutes.5. Rinse the slide with phosphate buffer once, and distilled water twice.6. Mount the slide using DPX or Canada Balsam by putting a drop of DPX or Canada Balsam on the slide before laying a coverslip over the preparation by holding the cover slip at a 45o angle to the drop and then slowly lowering the coverslip, over the drop forcing trapped air out of the preparation.7. Label your slide with your matric number, type of tissue eg

C. Epithelial tissue1. Examine the various epithelial tissue under low and high

magnification. Based on the structure of the cells, where do you think these cells are found in the body? Give an example where these cells are found in the body for each type of epithelial tissue.The slides to be examined include: a) columnar epithelium b) glandular epitheliumc) pigmented epithelium d) simple ciliated

columnar e) simple columnar f) simple cuboidal epitheliumg) simple squamous h) stratified columnar

epitheliumi) stratified squamous j) stratified squamous keratinizing epitheliumh) pseudostratified columnar ciliated epithelium Then, pick 2 slides and draw it under low and high magnification.

2. What are a) simple epithelial b) pseudostratified epithelialc) stratified epithelial d) squamous epitheliale) cuboidal epithelial f) columnar epithelialg) transitional epithelial

(TIP: Explain based on cell layers and morphology of surface cells)

3. What are goblet cells? Explain where goblet cells can be found in the body.

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UK 12345Epithelium(cheek)

4. Give two differences between an exocrine and endocrine gland. For each type of gland, give an example and where is it found in the body.

5. Exocrine glands can be classified according to the shape of the secretory part and the nature of the ducts. Name these different classifications and give an example for each different exocrine gland.

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