Histology is the study of tissues at a microscopic level. It involves preparing tissue samples using processes like fixation, dehydration, embedding, sectioning, and staining. Different types of microscopes like light, transmission electron, and scanning electron microscopes are used to examine cells and structures at varying levels of magnification, resolution, and contrast. Common staining techniques include hematoxylin and eosin, periodic acid-schiff, and trichrome stains which allow visualization of different cellular components. Histochemistry and immunocytochemistry further aid in localization of macromolecules within tissues.

1. INTRODUCTION TO
HISTOLOGY
Prof. Redem C. Deligero, MATMRS;MSES

2. DEFINITION
 Histology is the branch of anatomy that
deals with the study of tissues in animal and
plants.
 It deals with the structure and its function.
 This subject itself intertwines the discipline in cell
biology, biochemistry, physiology and pathology.

3. MICROSCOPY
 Is the method used in the study of cells
and its structure using microscope.
Major Kind of Microscope
1.Light Microscope – Utilizes light for
illumination.
2.Electron Microscope – Uses an electron
beam.

4. LIGHT MICROSCOPE

5. TRANSMISSION ELECTRON MICROSCOPE

6. SCANNING ELECTRON MICROSCOPE

7. 3 IMPORTANT PARAMETERS IN
MICROSCOPY
1. Magnification – It is the ratio between the size
of an image produce by the microscope and its
actual size.
2. Resolution – A measure of clarity of an image.
3. Contrast – The ability to visualized a particular
cell structure depending on how different it
looks from an adjacent structure.

8. TISSUE PREPARATION
1. Fixation – treatment of tissue with chemical
agent.
2. Dehydration & Clearing – removal of water from
tissue sample.
3. Embedding – Infiltration of tissue sample with
paraffin.
4. Sectioning – Cutting tissue sample by section into
specific equal increments.
5. Mounting and Staining – Placing the tissue
sample on adhesive glass slides.

9. FIXATION

10. DEHYDRATION & CLEARING

11. EMBEDDING

12. SECTIONING

13. MOUNTING AND STAINING

14. 3 MAJOR CATEGORY OF STAINS
1. Stains that differentiate between acidic
and basic cellular components.
2. Specialized stains that differentiate the
fibrous components of the extracellular
matrix.
3. Metallic salts that precipitate on tissue
forming metal deposits.

15. COMMONLY USED STAINS
1. Hematoxylin – Forms the basophilic
components of the cell.
2. Eosin – Forms the acidophilic
components of the cell.
3. Toluidine Blue – Forms the
metachromatic component of the cell.

16. HISTOCHEMISTRY
1. Periodic Acid Schiff (PAS) - Is a staining method used to
detect polysaccharides (e.g. glycogen, glycoproteins,
glycolipids and mucins in tissues.
2. Feulgen Reaction - Is used to identify chromosomal
material or DNA in cell specimens.
3. Gomori-Takamatsu - a method for localizing the alkaline
phosphatase enzyme.
4. Mordant - Is a substance used to set dyes on tissue
sections by forming a coordination complex with the dye
which then attaches to the tissue.It may be used for
intensifying stains in cell or tissue preparations.
5. Counterstain - Is a stain with colour contrasting to the
principal stain, making the stained structure more easily
visible.

17. HEMATOXYLIN

18. EOSIN

19. MASSON'S TRICHOME

20. ORCEIN'S ELASTIC STAIN

21. WEIGERT'S ELASTIC STAIN

22. SILVER STAIN

23. IRON HEMATOXYLIN STAIN

24. PERIODIC ACID-SCHIFF

25. WRIGHT AND GIEMSA STAINS

26. ADVANCE VISUALIZATION PROCEDURES
1. Hitochemistry

A method if tissue staining that gives
information on the presence and location of
intracellular and extracellular
macromolecules.
2. Immunocytochemistry

It uses flourescenated antibodies &
antiantibodies to exact intracellular and
extracellular localization of macromolecules.

27. 3. Autoradiography

A method that incorporates radioactive
isotopes into macromolecules which are then
visualized by an overlay of film.

It uses a radio isotopes tritium (3
H).

28. UNITS OF MEASUREMENT
1. Micrometer (µm) – This corresponds to
one-millionth of a meter (10-6
m )
2. Nanometer (nm) – This corresponds to
one-billionth of a meter (10-9
m)
3. Angstrom (Å) -This corresponds to one
ten-billionth of a meter (10-10
m)