Introduction to histology

Dr. Samah Kotb2015

Histology Techniques CLS 322

Objectives to learn histology

To understand what is Histology.

To understand the importance of Histology in medical

field.

To recognize the normal microscopic features of all

organs of human body.

Introduction to histology

Definition of histology:

Histology is the study of the tissues of the body and

how these tissues are arranged to constitute organs.

Importance of histology in clinical field

Histology is the science that tells about the normal

microscopic feature of all the cells and tissues in the

body.

Histology is the step before going to understand the

pathology of diseased tissues.

Histological techniques or procedures

To study the microscopic features of cells and tissues, the

tissues are processed through various stages to be

viewed under microscope, all these steps are called

HISTOLOGICAL TECNIQUES OR PROCEDURES.

• In the past manual methods were used; but histotechnology

has now advanced to a paramedical science of automation

and advanced techniques to help the pathologist in

diagnosis.

• Histotechnologist should not only know what to do; but

should also know the principle and the theory of what he or

she is doing.

Histotechnology

• To Demonstrate such structures; the tissue must be

prepared in such a way to allow microscopically

observation and study of these different structures.

• This preparation includes the preservation of tissue

materials, processing of tissue block, cutting and staining

of thin sections.

1.Fixation

2.Dehydration

3.Embedding

4.Cutting

5.Staining

Techniques These techniques are :

Surgical Specimen

Fixation

Taking Samples

Dehydration and Clearing

Embedding

Sectioning

Picking up sections

Microscope slide preparation

Staining

Cover Slipping

Reporting

PREPARATION OF TISSUES FOR STUDY

Biological tissues must undergo a series of treatments

to be observed with light and electron microscopes.

The process begins by stabilization of the tissue with

chemical fixatives.

Next, the tissue is made rigid to allow sectioning.

Finally, it is stained to provide contrast for

visualization in the microscope.

1.Fixation

Techniques

Preserves cellular structure and maintains the

distribution of organelles.

Formaldehyde the most commonly used chemical

fixatives.

2.Dehydration

Techniques

The water is first extracted from the fragments by

bathing them successively in a graded series of

mixtures of ethanol and water, usually from 70% to

100% ethanol (dehydration).

Techniques

The liquid form of the embedding compound, for

example, paraffin wax, replaces the intermediate

solvent.

The liquid embedding medium is allowed to

solidify, thereby providing rigidity to the tissue for

sectioning.

3.Embedding

Techniques

The hard blocks containing the

tissues are then placed in an

instrument called a microtome

and are sliced by the microtome's

steel or glass blade into sections

1 to 10 micrometers thick.

4.Cutting

Techniques

To be studied microscopically sections must typically

be stained or dyed because most tissues are colorless.

Methods of staining tissues have therefore been

devised that not only make the various tissue

components clear but also permit distinctions to be

made between them.

5.Staining

There are various stains used to make histology slides, commonly used are the following:

STAIN TISSUES

Haematoxyline Stains nucleus of cell (blue)

Eosin Stains cytoplasm of cell (pink)

Masson’s trichome

Stains connective tissue

Wright’s stain Stains blood cells

Periodic acid Schiff(PAS)

Stains basement membrane

BASIC HUMAN BODY TISSUES

Human body tissues are classified into four basic types.

1.Epithelial tissue 2.Connective tissue

3.Muscular tissue 4.Nervous tissue

BASIC HUMAN BODY TISSUES

1.Epithelium:

Covers body surfaces, lines organs and cavities.

BASIC HUMAN BODY TISSUES

2. Connective tissue: The different types of connective tissue are

responsible for providing and maintaining the form of organs throughout the body.

provide a matrix that connects and binds other tissues and cells in organs

BASIC HUMAN BODY TISSUES

3.MUSCULAR TISSUE:

Histological, there are three types of muscular tissues, all

responsible for different kind of movements.

BASIC HUMAN BODY TISSUES

4.NERVOUS TISSUE:

It is the main component of the nervous system - the

brain, spinal cord, and branching peripheral nerves.

It is composed of neurons and neuroglia cells.

Thank you