MICROSCOPE HISTO 1

Lesson 1.2: Microscope

Rules for Microscope Use

  • Carry with two hands.

  • Clean lenses with lens paper only.

  • Do not force adjustment knobs.

  • Always cover after use.

  • Handle cords carefully.

Two Basic Types of Microscopes

  1. Light Microscope - Uses light to view samples.

  2. Electron Microscope - Uses electron beams for higher magnification.

Parts of a Light Microscope

  • Eyepiece: Magnifies image from the objective lens (usually 10x).
    Body Tube: Maintains alignment between lenses.

  • Nosepiece: Holds and rotates objective lenses.

  • Objectives:
    Scanning (4x, red)
    Low Power (10x, yellow)
    High Power (40x, blue)

  • Arm: Connects base and supports upper parts.

  • Stage: Platform where the slide is placed.

  • Stage Clips: Hold slide in place.

  • Diaphragm: Controls light amount on specimen.

  • Coarse Focus Knob: For large adjustments (used first).

  • Fine Focus Knob: For detailed focusing.

  • Light Source/Mirror: Provides illumination.

• Base: Supports the microscope (foot or horseshoe-shaped).

Eyepieces (Ocular Lens)

Head

(frame

Diopter Adjustment

Nose Piece

Objective Lenses

Stage Clip

Mechanical

Stage

Condenser-

• Aperture

Stage

Controls

Illumination

Light Switch

Coarse

Adjustmer

Fine

Adjustment

Brightness Adjustment

Base

Magnification Calculation

• Total Magnification = Eyepiece ×

Objective lens

Example: 10x eyepiece x 40x objective =

400x

Steps to Use the Microscope

  1. Place slide on stage and secure with clips.

  2. Start with lowest power objective.

  3. Look through eyepiece.

  4. Use Coarse Focus, then Fine Focus.

  5. Switch to higher powers as needed.

Tissue Preparation for Light Microscopy

  1. Fixation: Preserves tissues using chemicals.

  2. Dehydration & Infiltration: Replace water with paraffin or plastic.

  3. Embedding: Solidify tissue in a block.

  4. Sectioning: Slice into 3-10 um thin sections.

  5. Staining:

Hematoxylin (basic dye): Stains basophilic structures (e.g., nucleus) blue/purple.

Eosin (acidic dye): Stains acidophilic structures (e.g., cytoplasm) red/pink.

Types of electron microscope

1. Transmission Electron Microscope

(TEM)

Electron beam passes through the specimen.

Produces a 2D image.

• Used to observe internal structures (e.g., organelles).

2. Parts of TEM:

Illumination Source: Produces electron beam.

  • Condenser Lens: Focuses the beam.

  • Specimen Stage: Where sample is placed.

Objective Lens: Initial magnification.

  • Projection Lens: Final magnification and image projection.

  • Fluorescent Screen: Displays the image.

  • Viewing Window: For observer to see image.

  • Uses heavy metal stains, gives black and white images.

3. Scanning Electron Microscope (SEM)

  • Electron beam bounces off specimen surface.

  • Produces a 3D image of external features.