Continuation to Introduction

Histopathology derive from the word histo and pathology. Histo means tissues while pathology indicates disease processes or changes. Before tissues are processed, they are pre-fixed in chemicals called fixatives. The specimens are sent in fixatives to the laboratory where they are registered and given histology number. This number is the laboratory number used for the processing of the specimen. Registered samples at Reception are transfered to the cut-up room for selection. Once part of the tissues are selected depending on the pathology presented, they are capped in tissue cassettes and transfered to the alcohol bath for processing starting from dehydration.

It is important to ensure that fixation is complete before tissue processing.
The aim of tissue processing is to embed the tissue in a solid medium firm to give support to the tissue to enable thin section to be cut and also soft to allow microtome blade to cut the sections. And the most embedding medium used in histopathology laboratory is paraffin wax.
DEHYDRATION
This is the first stage in tissue processing after proper fixation, it involves the removal of water from tissue, grades of alcohol are used, the concentration ranges from 70% alcohol to absolute alcohol, and tissue pass from 70% to absolute alcohol, tissue must be completely dehydrated before going into the next stage which is clearing to ensure the clearing agent and wax penetrate the tissue completely.
CLEARING
This is the next stage after dehydration, it involves removal of absolute alcohol and the replacing the processing solvent called xylene, which is miscible with both absolute alcohol and paraffin wax.
IMPREGNATION
Also called called infiltration, it involves the process of replacing the the xylene with molten paraffin wax.
EMBEDDING
Embedding is the process of placing the tissue in a embedding mould containing molten paraffin wax and it become solid when it is cold. This form solid support for tissue during microtomy on the microtome machine, it is important to properly orientate the tissue during embedding to ensure complete representation of all part of the tissue in the cut sections.

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THE EFFECTS OF AQUEOUS EXTRACT FROM Khaya senegalensis ON THE HISTOLOGY OF LIVER AND KIDNEY OF ALBINO RATS

Abstract
Lasisi, E.M. Octoder 2008.
The stem bark of Khaya senegalensis was extracted and administered using aqueous method with the aim determining the effect of Khaya senegalensis (300mg/kg body weight) on liver and kidney of white albino rats. Experimental animals were randomly divided into 7groups with each group consisting of 5rats. Group 7 consists of the control and was orally administered with distilled water. Group 1, 2,3,4,5 and 6 consist of test animal received 300mg/kg dosage of the extracts on repeated basis for different numbers of days for 25days.
The result obtained from the study suggested that prolonged oral administration of aqueous extract from stem bark of Khaya senegalensis showed significant changes on the histology of liver and kidney of white albino rats.

Introduction

Histopathology derive from the word histo and pathology.
Histo means tissues while pathology indicates disease processes or changes.
Before tissues are processed, they are pre-fixed in chemicals called fixatives. The specimens are sent in fixatives to the laboratory where they are registered and given histology number. This number is the laboratory number used for the processing of the specimen.
Registered samples are transfered to the cut-up room for selection. Once part of the tissues are selected depending on the pathology presented, they are capped in tissue cassettes and transfered to the alcohol bath for processing starting from dehydration.