How can a light microscope be used to investigate cell and tissue structure, and what steps are involved in drawing cells, calculating magnification, and determining the actual size of structures seen in drawings or micrographs?

Sourav PanNovember 7, 2024

Answered

Using a light microscope to investigate cell and tissue structure involves several steps, including sample preparation, observation, drawing, calculating magnification, and determining the actual size of observed structures. Here’s a detailed guide on how to perform these tasks effectively.

Using a Light Microscope

1. Sample Preparation:
   • Fixation: Preserve the tissue sample using formalin or another fixative to prevent degradation.
   • Processing: Remove water from the tissue by replacing it with ethanol, followed by xylene to facilitate embedding.
   • Embedding: Embed the tissue in paraffin wax to create a solid block that can be sliced into thin sections using a microtome (typically 4 μm thick).
   • Mounting and Staining: Place the thin sections on glass slides and stain them (commonly with hematoxylin and eosin) to enhance contrast and visibility of cellular structures.
2. Observation:
   • Use the light microscope to view the prepared slides. Adjust the objective lens to the desired magnification (e.g., 10x, 40x, or 100x) for detailed observation of cells and tissues.

Drawing Cells

When drawing what you observe under the microscope:

• Title and Labeling: Start with a clear title for your drawing. Label important structures accurately, such as nuclei, cell walls, and any other visible organelles.
• Proportions: Maintain accurate proportions relative to what you see; avoid exaggeration.
• Detail: Include enough detail to represent the structure accurately but avoid overcrowding your drawing with unnecessary information.
• Scale Bar: If possible, include a scale bar to indicate size.

Calculating Magnification

To determine the total magnification when viewing a specimen through a light microscope:

1. Identify Objective Magnification: Check the magnification power marked on the objective lens (e.g., 4x, 10x, 40x).
2. Eyepiece Magnification: The eyepiece typically has a fixed magnification of 10x.
3. Calculate Total Magnification:
   $$\text{Total Magnification}=\text{Objective Magnification}\times \text{Eyepiece Magnification}$$

   For example, if using a 40x objective lens:

   Total Magnification=40x×10x=400x

Determining Actual Size of Structures

To find the actual size of structures observed in your drawings or micrographs:

1. Measure Size in Drawings: Use a ruler to measure the size of the drawn structure in millimeters or centimeters.
2. Convert Measurement to Micrometers: Convert this measurement into micrometers (1 mm = 1000 µm).
3. Calculate Actual Size Using Magnification:
   Actual Size=Measured Size/Total Magnification​

   For example, if a structure measures 2 mm in your drawing at 400x magnification:

   • Convert measurement: 2 mm=2000 m
   • Calculate actual size:
   Actual Size=2000 m/400=5 m