Histology-Introduction to histology and H&E staining

Introduction to histology and H&E staining 

 Histology consists of two Greek words, histo means tissue and logia means study or knowledge, histology literally means knowledge of tissue.

Histology is study of microstructures and define the relationship between the structure and function of human body.

There are four basic tissue:

Epithelium, connective, muscular and nervous tissue and Organ made up of tissue, and they have special shape and functions.

Histology studies the microstructures. So, we should have the aid of microscope to study. There are two common types of microscopes are available; light microscope, electron microscope.

Figure 1. Light microscope

Preparation of tissue for light microscopy

• obtaining: First, we need to obtain the specimen, fresh, small pieces (less than 5 mm³).
• Fixation: Then we have to preserve the structural organization of the tissue by using formalin or Bouin’s.
• Dehydration: We use ethyl alcohol to get rid of water of tissue
• clearing: Then use xylene to get rid of alcohol.
• embedding: we heat the paraffin, make it melt, then we put tissue block into melted paraffin, allow paraffin harden, the tissue block is embedded in.
• sectioning: use microtome to cut the tissue into 3-8um thick sections.
• Mounting: Then we mount sections on glass slides
• Observation: At the end we can observe by LM (light microscope).

Staining

Staining is used to highlight the important features of the tissues, otherwise it is almost impossible to enhance visualization of the cell, furthermore we use staining to differentiate the live and dead cells.

One of the most important staining is H&E staining.

H&E staining

Hematoxylin and Eosin are two histological stains. Hematoxylin is basic stain, which combines with acidic components, make them appear blue color, basophilic, for instance: cell nucleus and hyaline cartilage. On the other hand, Eosin is acidic stain which combines with basic components, make them appear pink color- acidophilic (eosinophilic), for example: cytoplasm.

Figure 2. example of H&E staining

Figure 3. H&E staining slides