Histology Methods of Study

Dr. Nour Erekat, PhD

Histology

• The study of the body tissues and how they are arranged to constitute organs– Dependent on the use of microscopes

• Due to the small size of cells and matrix components

Tissue Preparation for Histology

• Steps for tissue preparation1- Fixation

2- Embedding and sectioning

3- Staining

Fixation

• Aim– Preserve the structure and molecular

composition of the tissue• By avoiding tissue digestion

• Methods1- Physical (e.g. Freezing)

2- Chemical - Using fixatives (e.g. 37% formaldehyde)

Embedding and Sectioning

• Embedding– Aim

• Facilitate sectioning

– Embedding materials• Paraffin for light microscopy• Resins for both light and electron microscopy

• Sectioning– Microtome

• 1-10 µm (1-10 micrometers)

Staining

• Aim– Make tissue components conspicuous and distinctive

• Using dyes1- Basic

- Stain basophilic tissue components with a net negative charge (anionic)

- Hematoxylin

2- Acid- Stain acidophilic tissue components (cationic)

- Eosin

Staining

Microscopy

• Classification1- Electron microscopy

A- Transmission

B- Scanning

2- Light microscopy Bright-field microscopy

Components

1. Optical

2. Mechanical

Bright-Field Microscopy

• Optical components1. Condenser lens

2. Objective lenses• Quality determines resolving power (0.2 µm)

– Quality of image– Objective lenses of higher magnification have higher

resolving power

3. Ocular (eyepiece) lens

Bright-Field Microscopy