Microscopy and the Compound Microscope

Introduction to Microscopy and Laboratory Objectives

Nature of Anatomy Study: A comprehensive study of anatomy includes not only large, visible structures but also microscopic structures that provide an organism with its specific form and function.
Microscope Type: The laboratory uses compound, bright-field microscopes. These instruments use a combination of lenses to magnify and clarify microscopic objects.
Mechanism of Imaging: The specimen is illuminated with light, producing a dark or stained image viewed against a light background.
Parfocal Design: The microscopes are designed to be parfocal. This means that once an object is in focus at one magnification power, it should remain in focus (or very close to it) when switching to another power.
Laboratory Requirements and Self-Directed Learning: - The laboratory is a self-directed learning experience. - Students must use textbooks, lab books, Visible Body, and atlases to identify structures, functions, numerical values/units, and definitions. - Requirements for students include: - Identifying all structures visually, verbally, and in writing. - Defining all structural and physiological terms with correct spelling. - Knowing the location and function of every structure.

Anatomy of the Compound Microscope: Parts and Functions

Oculars (Eyepieces): - These contain the ocular lens. - Standard magnification is $10X$ . - Some models include a Diopter Adjustment to compensate for differences between the user's eyes.
Head: The upper portion of the microscope that holds the optical parts.
Body Tube: Connects the eyepiece to the objective lenses.
Arm (Frame): - Connects the head to the base. - Supports the microscope. - This is the part that must be grasped when carrying or moving the microscope.
Nosepiece (Revolving/Rotating Nosepiece): - An inclined, circular metal plate that holds multiple objective lenses. - It can be rotated to change the magnification power.
Objective Lenses: Optical lenses that collect light from the specimen and project a magnified image to the eyepiece. - Scanning Power: Red ring, $4X$ magnification. - Low Power: Yellow ring, $10X$ magnification. - High Power: Blue ring, $40X$ magnification. - Oil Immersion: White ring, $100X$ magnification (not always present).
Stage and Mechanical Stage: - Stage: The platform where the slide/sample is placed for viewing. - Mechanical Stage: Allows for precise movement of the slide. - Stage Clips: Used to hold the slide securely in place. - Mechanical Stage Knobs (X-Y Knobs): Used to move the slide horizontally and vertically across the stage.
Condenser: Located under the stage; it collects and focuses light from the illuminator into the specimen.
Iris Diaphragm: Regulates the amount of light reaching the specimen. Includes a lever for adjustment.
Adjustment Knobs: - Coarse Adjustment Knob: The larger knob used to move the stage up and down significantly to bring the specimen into general focus. Only used with scanning power. - Fine Adjustment Knob: The smaller knob used for fine-tuning the sharpness or detail of the image, especially at higher powers.
Illumination System: - Light Source (Illuminator/Substage Light): The bulb at the base that projects light upwards through the diaphragm, specimen, and lenses. - Rheostat (Light Adjustment/Brightness Adjustment): A control used to adjust the intensity of the light. - Power Switch: Turns the light source on and off.
Base: The bottom part that supports the entire microscope and houses the illuminator and power components.
Power Cord: Supplies electricity to the light source.

Calculating Magnification

Compound System: Because these microscopes use both ocular and objective lenses, the total magnification is a product of both lens powers.
Total Magnification Formula: - $\text{Total Magnification} = \text{Power of Objective Lens} \times \text{Power of the Oculars}$
Magnification Data Table:

Objective Lens	Objective Magnification	Ocular Magnification	Total Magnification
Scanning	$4X$	$10X$	$40X$
Low Power	$10X$	$10X$	$100X$
High Power	$40X$	$10X$	$400X$
Oil Immersion	$100X$	$10X$	$1000X$

Proper Microscope Use and Maintenance

Setup and Handling: - Grasp the arm when moving the microscope; do not grasp the body tube. - Ensure the power switch is off and light intensity (rheostat) is at the lowest setting before plugging it in.
Cleaning: - Use only provided lens paper and cleaning solution to clean oculars and objectives. - Do not use paper towels, as they are too abrasive and can damage the lenses.
Initial Focusing Procedure: - Rotate the nosepiece to the scanning power objective ( $4X$ , red ring). - Move the stage down using the coarse adjustment knob to create maximum working distance. - Place the slide between (not underneath) the stage clips. - Raise the stage to its highest position while on scanning power, then use the coarse adjustment to focus moving the stage away from the objective.
Transitioning Magnification: - Center the specimen in the field of view before switching powers. - Rotate to the low power objective ( $10X$ , yellow ring). - Use the fine adjustment knob slowly to sharpen the image. - Repeat the process for high power ( $40X$ , blue ring). Use only the fine adjustment knob at high power.
Storage and Cleanup: - When finished, rotate back to the scanning power objective. - Lower the stage using the coarse adjustment knob. (Never lower the stage or change slides while on high power to avoid driving the lens into the slide). - Return slides to their proper trays. - Clean the lenses again. - Replace the dust cover and return the microscope to its proper cabinet.