Tuesday, September 28, 2010

Trouble with tissues?

I don't think I've ever met a person who could identify tissues of the body on sight on their first day of trying. And yet many A&P students get frustrated just because they can't "get it" after only one day of trying. Identifying tissue types by sight is difficult for everyone, at first—for  several reasons.

First, each example is unique. No two examples look exactly alike, just like no two fingerprints look exactly alike.So you have to learn to look for patterns. And you can't do that until you've looked at a lot of examples. And that takes time—and a lot of practice.

Second, not all examples are stained in exactly the same way. Even when the same general type of staining is used, a lot depends on the quality of the sample, the quality of the stain used, and how well the preparer did their job. So again, you have to look for patterns. For example, stratified squamous epithelium can be found in wildly different colors, depending upon which type of staining technique is used. But no matter what the color, the pattern of flattened cells near the free edge, progressing to cuboidal and perhaps even column-shaped cells further away from the free edge, will still be present.

Third, when you look for patterns you have to remember what part of the pattern is important. You also have to remember that many patterns are very similar, so you have to remember how to tell them apart. For example, dense fibrous connective tissue can look a lot like fibrocartilage at first glance. You have to learn to look for the little white halos around the cells in fibrocartilage that tell you that the cells are within lacunae (spaces).

Oh, did I mention that practice, practice, practice is important?

Tissue identification really isn't as hard as it first seems. It really is mainly just a matter of putting the time into practicing.

Here are some tips for getting the most practice time in during the short time you have studied tissues:
  • Spend as much time in the lab as possible. If there are open lab times available, by all means take advantage of it.

  • If there is a learning center available with tissue specimens spend as much time as you can with them.

  • Use the examples published in your textbook and lab manual, or any other resource (such as a Brief Atlas of the Body),to practice identifying tissues. Cover up the labels and see if you can identify them. Make a photocopy of the images, cutaway or cover-up the labels, and test yourself.

  • Ask your instructor for other sources of practice images. Sometimes, someone will have taken photographs of the specimens used in your class. This is a good resource for practicing.

  • There are a lot of online resources for practicing tissue identification. Here are a few of my favorites – you can find many more by searching the web using key terms such as "tissues," "histology," and similar terms.

    • LUMEN
      [Loyola University's famous histology site; includes lessons on histology]

    • Blue Histology
      [Histology site at School of Anatomy and Human Biology, University of Western Australia]

    • Dr. Stephen Larsen's Channel (YouTube)
      [Dr. Larsen walks you through a variety of specimens as they are seen under the microscope.]

    • The A&P Professor Free Image Library
      [My site for A&P teachers includes links to free images of tissues that you can use to practice histology.]

  • Use flash cards (study cards) with photocopies of tissue specimens or printouts of digital images. See my recent blog article for a video on how to use flash cards in this manner.  Mosby's Anatomy & Physiology Study and Review Cards includes some histology cards along with all other topics in A&P.

  • Try to study a little bit several times each day, rather than a few long sessions several days apart. Constant practice is what works best.
The introduction to my Field Guide to the Body at the Lion Den website compares studying tissues to what birders do when they identify wildlife in the field. Take a look at that brief analogy, including examples of how to apply it to histology, for helpful tips on making this topic easier. If you're using any of my lab manuals in your A&P course, you can apply this technique directly by looking at the "Landmark Characteristics" boxes scattered throughout the tissue exercises.

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