Tissue is composed of a group of similar cells and their products that perform specific functions.
Histology is the study of tissues, and the microscope is the primary tool for analysis. While the human
body contains several trillion cells and more than 200 cell types, when it comes to tissues they are divided
into four basic tissue types: epithelial, connective, muscle, and nervous. Each of them has a specific func-
tion and as such allow different structures in the body to perform their tasks.
During each of the exercises, representative examples of each tissue type will be observed under the micro-
scope. Review the proper techniques for microscope use if needed. Most of the samples in this lab are sec-
tions of various organs that might be composed of two or more tissue types. With that in mind and before
the section is observed under the microscope, follow the outlined steps for tissue observation for optimal
and fast tissue characterization

1. It is important to know from which organ the section comes and what kind of plane of sectioning was
used. This will help in the orientation and localization of the tissues of interest. How many planes of
sectioning are there?

2.
Once the sample is on the microscope (remember to start with the scanning power objective) and is in
focus, carefully observe the section and localize the area of the sample where the tissue of interest is
found. The scanning power objective is a good choice for such observation due to the large field of

3. When the location of the tissue of interest is narrowed down, move that area of the section to the
middle of the viewing field. Which part of the microscope is used for stage movement?

4.
Move to the low power objective and focus, making sure that the area of the sample with the tissue
of interest is in the middle of the viewing field. If it is not, move the sample. Only one focusing knob
should be used from this point on. Which one?
After focusing and observing at low magnification power, turn to the high power objective, focus
again, observe the shape and arrangement of the cells and material between the cells, and sketch the
image in the appropriate area in the lab manual.

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If in doubt, refer to laboratory charts with images of tissues, textbook figures, and the instructor.
imens of all tissues are stained with various dyes so that details of the cells and the extracellular
visible Unstained tissues and cells are light, and it is very difficult to distinguish cells from
the surrounding material and any morphological (structural) details.