Principles of Medical Laboratory Science II - Overview

C. Arm

Structure that supports the magnifying and adjusting systems; also the handle used to carry the microscope.

D. Stage

A horizontal platform or shelf on which the object being observed is placed by stage clips.

Simple Microscope

Single set of magnifying lens that enlarges objects that are difficult to view with an unaided eye.

Compound Microscope

Has two separate lens systems: eyepiece and objectives, requiring total magnification.

A. Source of Light

Built in bulb located at the base of the microscope with an on/off switch.

Types of Bulb

Includes Tungsten, Tungsten-halogen (most common), and Light emitting diode (LED).

Type of Light Source

Includes Visible Light (most common, for compound), Ultraviolet Light (mercury lamp), and Laser.

B. Rheostat

Also called as a light control knob, dimmer switch, or slide; regulates brightness.

C. Condenser

Directs and focuses the beam of light from the bulb onto the material under examination.

B. Base

Horseshoe-shaped foot on which the microscope rests; where light source are found.

1. Abbe-type condenser

Has its own internal lens (not included in the counting of lens system), only used to focus the light.

2. Achromatic (or Aplanatic) condenser

Reduce color distortion; designed to correct chromatic and spherical aberrations, providing better image clarity and contrast.

A. Ocular/Eyepiece

Can be monocular or binocular; magnifies the image formed by the objective, usually with a magnification of 10 (10x).

B. Objectives

Determines the quality of images the microscope can produce.

D. Aperture Iris Diaphragm

Located at the bottom of the condenser; controls the amount of light passing through the material under observation.

Scanning Objective (4x)

Used for initial scanning in the morphologic examination of histologic sections.

Low-Power Objective (10x)

Used in the initial focusing and light adjustment of the microscope. Use if the specimen is very small.

High-Power Objective (40x)

Used for more detailed study, it has a short working distance, so care must be taken during focusing.

Oil-Immersion Objective (100x)

Has the highest magnification and shortest working distance. It requires immersion oil to be placed between the objective and the slide.

Bright-Field Microscope

The most common type of light microscope used in the laboratory, best for stained specimens.

Parfocal

When the focus is using one objective, it will remain mostly in focus when the higher objective is switched in place.

Parcentric

A specimen centered in the field of view for one objective remains centered when the nosepiece is rotated to bring another objective into use.

Oculars

Part where the light passes through to the ocular and conducts the image of the object being observed.

Body Tube

The tube length from the eyepiece to the objective lens is generally 160 mm.

Adjustment System

Enables the body tube to move up or down for focusing the objectives.

Coarse Adjustment Knob

Gives rapid movement over a wide range to obtain an approximate focus. This is used with the Scanning and LPO.

Fine Adjustment Knob

Gives very slow movement over a limited range to obtain exact focus after the coarse adjustment.

Phase-Contrast Microscope

Best use for viewing transparent, colorless, or unstained specimens like urine, and cells in the hemocytometer.

Field Diaphragm

Located in the light port in the base of the microscope, it controls the area of the circle of light in the field of view.

Rheostat

Adjusts brightness.

Iris Diaphragm

Controls contrast and light flow.

Condenser

Focuses and directs light.

Specimen

The object being viewed under the microscope.

Annular Diaphragm

Designed to let a hollow cone or 'doughnut' of light pass through the condenser.

Absorption Ring

Used in conjunction with the annular diaphragm.

Unstained Specimen

Can be viewed in the Brightfield Microscope but with limitations.

Light Microscope

Has two lens systems, one in the oculars and another in the objectives.

Dark-Field Microscope

Best for viewing surface details, thin specimens, and unstained cells.

DIC (Differential Interference Contrast) Microscopes

Best for viewing Amyloid deposits, which are build-ups of proteins.

Epi-Fluorescence Microscope

Uses ultraviolet light to illuminate the specimen and is used to view objects stained with fluorescent dye.

Polarizing Microscope

Produces a bright image on a dark background, useful for viewing and identifying crystals such as calcium oxalate.

Birefringence

An object with birefringence will split a beam of polarized light into two light beams, resulting in a colored image.

Transmission Electron Microscope (TEM)

Passes electrons through a thin specimen, creating high-resolution, 2D images of internal structures.

Confocal Laser Scanning Microscope (CLSM)

Produces images with excellent resolution and can create a 3-D or stereo image that can be digitally manipulated.

Fluorophores

Preferred with high contrast and photostability for imaging.

High Contrast

The quality that makes it easier to observe living or moving cells against a black background.

Syphilis

A well-known spirochete caused by Treponema pallidum.

Iris Diaphragm

Located on the top of the microscope, used to control the amount of light reaching the specimen.

Excitation Light

Depends on the specific fluorochrome/fluorophore used, which has its own wavelength.

Immunofluorescence Assays (IFA)

Used for detecting antibodies in various conditions, including syphilis and lupus.

Electron Beam

Used in scanning to detect secondary or reflected, emitted, backscattered electrons from the specimen's surface.

3-D or Stereo Image

Created by merging a series of images captured from different planes of focus.

Nanomaterials

Studied using Transmission Electron Microscopes for fine cellular details and molecular structures.

Cork Screw Motility

A type of movement observed in spirochetes.

H&E Stain

A staining technique used in histology to highlight cellular structures.

Congo Red Stain

Used to identify amyloid deposits in tissues.

Specimen

A sample used for examination under a microscope.

Living Cells

Cells that can be observed using high contrast techniques in microscopy.

Microorganisms

Organisms that can be identified using polarizing and DIC microscopes.

Internal Organelles

Cell structures that can be viewed using a Dark-Field Microscope.

ELECTRON MICROSCOPE

A type of microscope that uses electrons to illuminate a specimen and create an enlarged image.

2-PHOTON MICROSCOPE

View thick and live specimens. Use fluorescence. Can magnify the image of a specimen up to 2 million times. Highest magnification possible. Not colored.

Scanning Electron Microscope (SEM)

View thick samples. Examining external structures, morphology, topography, 20 nm. Produces detailed 3D images of a specimen.

Resolving Power (μm)

This refers to the microscope's ability to distinguish two points as separate. A lower resolving power value means better resolution (clearer details).

Low Power (1.34 μm)

Least detailed images.

Oil Immersion (0.26 μm)

Best resolution, ideal for very small structures like bacteria.

Numerical Aperture (NA)

NA represents the lens' ability to gather light and resolve fine details. A higher NA means better resolution and brighter images.

Low Power (0.25 NA)

Less light gathered, lower resolution.

Oil Immersion (1.30 NA)

Gathers the most light, providing the sharpest image.

Magnifying Power (x)

This indicates how much the objective enlarges the image.

Low Power (10x)

Used for scanning and overviewing specimens.

High Dry (40x)

Used for detailed viewing without oil.

Oil Immersion (100x)

Highest magnification, requires immersion oil to reduce light refraction.

Care and Cleaning of the Microscope

Always handle the microscope with care. Do not drag a microscope across the surface of a work area.

Misalignment of Optical Components

The lenses and mirrors inside the microscope can shift, affecting image quality.

Damage to the Mechanical Parts

The focusing knobs, stage, or revolving nosepiece can become loose or misaligned.

Risk of Dropping or Tipping Over

Microscopes are heavy, and dragging them might cause them to fall or get damaged.

Loosening of Electrical Components

If the microscope has a built-in light source, dragging it could loosen the bulb or its wiring, leading to flickering or failure.

Cleaning Agents

A cleaning agent may be used to clean the exterior of the microscope. A soft cloth or gauze should be used when cleaning.

Keep the lenses meticulously clean

Cleaning agents should not be used (Alcohol, Hypochlorite). Always use lens paper for cleaning.

Do not touch the lenses with your fingers

Always use lens paper for cleaning.

Keep the stage and adjustment knobs clean

Thoroughly clean and oil-free.

Do not turn the coarse adjustment knob when using the high-power and oil immersion objectives

This can damage the microscope.

Keep the microscope covered and free from dust when not in use

This helps maintain the integrity of the microscope.

Store with the 10x objective in place

And the body tube barrel adjusted to the lowest possible position.

Working Distance

The distance between the objective lens and the specimen when in focus.

Low Power

7.20 mm → Safest to use, more space.

Oil Immersion

0.20 mm → Very close to the specimen, requires precision to avoid damage.

Rheostat

Controls the amount of light that goes out through the light source.

Aperture Iris Diaphragm

Used to adjust the light through the condenser.

Phlebotomy

The act or practice of bloodletting as a therapeutic measure.

Leeching

Used in localized bloodletting.

Venesection

Also known as phlebotomy.

Stone Age Phlebotomy

Believed to be the earliest date of phlebotomy, crude tools were used to make incisions and drain blood.

1400 BC Bloodletting

Bloodletting using leeches was observed in a painting from a tomb in Egypt, Greece, Rome, and other Parts of Europe.

1210 AC Short Robe Surgeons

Guild of Barber-Surgeons were prohibited to perform any type of surgery except bloodletting.

Barber Pole Symbolism

The red represents blood, white represents bandages, and the spiral design mimics twisted bandages.

Long Robe Surgeons

Considered as real doctors, trained professionals who performed surgeries.

Present-Times Phlebotomy

Used to obtain blood samples for diagnosis, treatment (polycythemia), and monitoring.

Phlebotomy Basics

The process of collecting blood.