Histology introduction

Histology It is the study of the tissues of the body and how these tissues are arranged to constitute organs also called Microscopic anatomy Or Microanatomy.

Preparation of tissue For Light Microscopy ( Tissue Processing) The aim of tissue processing is to embed the tissue in a solid medium firm enough to support the tissue and give it sufficient rigidity to enable thin sections to be cut , and yet soft enough not to damage the knife or tissue with preservation of the structure with the least possible alteration.

Tissue Processing Fixation Dehydration Clearing Embedding Sectioning Sliding Staining Covering

Collecting the Sample Clinical Details Adequate specimen

Fixation Time require is almost 1mm/hour fixation To preserve the structure of tissue Achieved by the influence of various chemical compounds called Fixative . Common methods - 10% formaldehyde Time require is almost 1mm/hour fixation It is also used protect the tissue from the microorganisms

Dehydration Is the removal of extractable water from the tissue. Graduated strength of ethyl alcohol is routinely employed at series consisting of 30,50,70,95 and 100% alcohol produce good result. Average time required is 20-30 min in each solution

Clearing Also called dealcoholation. The aim of this process is to replace alcohol by a solvent which is miscible with paraffin. Xylene and chloroform are the most commonly used.

Embedding Before sectioning of tissue it must be embedded in a material which after hardening has a consistency that permits it to be cut into thin section. Paraffin wax is the most frequency used agent. During embedding process paraffin heated to 60 degree, and in cooling the paraffin with the tissue forms a firm tissue block.

Sectioning Sectioning is carried out by the help of machine called Microtome. Usually 3-10 µm thick

Sliding Also called mounting of the slide. Clean microscopic glass slid are taken and the section which is floated in warm water is taken on the glass slid in such a way that no air bubble is trapped between them. The dish is always has black ground with rounded edge

Staining Because the tissue of the body are colourless and it’s difficult to study their details the staining techniques enhance natural contrast and permits distinction to be made between them. When the colouring property of the dye is in the basic radical the stain is called basic dye and the stained structures called Basophilic . On the other hand, When the colouring property of the dye is in the acidic radical the stain is called acidic dye and the stained structures called Acidophilic.

Automated Manually

Cont… The most commonly used dye is a combination of HEMATOXYLIN and EOSIN ( H&E) To do it you must go in reverse order process because this stain dissolve in water. By this method the nuclear structures are stained dark purple or blue and all cytoplasmic structures and intracellular substances are stained pink

Covering Applying a thin glass coverslips to protect the section

Light microscope

Different Parts of Microscope Eyepiece Lens Tube Arm Base Illuminator Stage Revolving Nosepiece Objective Lenses Condenser Lens Coarse & fine Focus Diaphragm

Find good histology websites Study with a group of friends Learn the general characteristic of the four type of tissue Find good histology websites Study with a group of friends Look at histology images that weren't presented in lecture

Smile. It's important to try to have fun as you study histology Smile! It's important to try to have fun as you study histology. A good attitude will carry you a long way.