Preliminary Pages

fm1Practical Histology for Medical Students

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Practical Histology for Medical Students

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Practical Histology for Medical Students

SR Prasad MBBS, MS (Anatomy) AN Magadh Medical College Gaya

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Jitendar P Vij

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Practical Histology for Medical Students

All rights reserved. No part of this publication should be reproduced, stored in a retrieval system, or transmitted in any form or by any means: electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the author and the publisher.

This book has been published in good faith that the material provided by author is original. Every effort is made to ensure accuracy of material, but the publisher, printer and authors will not be held responsible for any inadvertent error(s). In case of any dispute, all legal matters are to be settled under Delhi jurisdiction only.

First Edition: 2007

9788180619137

Typeset at JPBMP typesetting unit

Printed at Gopsons Papers Ltd., A-14 Sector 60, Noidafm5

Foreword

Remembring that the aim of this book is to cover all the needs of undergraduate students, the “Practical Histology for Medical Students” has been written in a lucid language having simple and concise histological aspects of tissues and organs of the human body.

The book consists of two sections dealing with tissues and organs with a provision of space for drawing diagrams. In this book only principle features of basic tissues and organs have been described, therefore details of structure require consultation from the text book of Histology.

Identifying features of tissues and organs, as seen under light microscope, have been described very clearly in concise way, therefore, this book is very useful to the undergraduate and postgraduate medical students for the learning of histology.

Aruna Sinha

MBBS, MS (Anatomy)

Ex. Principal and Head of the Dept. of Anatomy

Jawaharlal Nehru Medical College, Bhagalpur

And

Ex. Dean, Faculty of Medicine

TM Bhagalpur University, Bhagalpur

And

Retd. Additional Director

Health (Medical Education and Indigenous Medicine)

Department, Govt. of Bihar, Patnafm6 fm7

Preface

Rapid progress of histology in understanding histopathology, cell biology, genetics and immunology has ushered in a new era in the development of basic medical sciences. Availability of electron microscope and other types of highly sophisticated microscopes have changed the trends of research activities.

This practical histology book has been written for undergraduate medical students with a provision of space for diagram might be helpful in their practical classes. This book might help them for a quick revision during pre-examination period. This book also will be very useful as a refresher book during their paraclinical and clinical classes.

In this book, electron microscopic features have been avoided. The complex cell structures and cytoplasmic organelles have not been discussed. Here, structures as seen in light microscope under low power magnification have been discussed. Only important slides shown in undergraduate classes under light microscope have been covered in this book.

I have to acknowledge help from my colleagues. Special mention must be made to Dr Mirza Hasnain who has given valuable time and opinions.

I will be grateful for comments and suggestions for improvement so that I incorporate them while bringing out the next edition.

SR Prasad fm8 fm9 fm10 fm11

Introduction

Anatomy is the branch of science concerned with study of structural organization of plants and animals. Here, we are concerned with human anatomy.

Broadly anatomy is divided into two parts:

Macroscopic Anatomy (Gross Anatomy)–Structures are studied by nacked eye examination.
Microscopic Anatomy–Study of minute parts, beyond the reach of nacked eye, with the help of microscope.

Previously histology and microscopic anatomy had separate wings. Histology was dealing with study of basic tissue of body, where as microscopic anatomy was dealing with organs of body. Nowadays histology includes microscopic anatomy to study the normal structures of tissues and cells forming organs and systems. Histology provides information essential to the development of histopathology which is dealing with the structures of sick. Histological study is very important in understanding pathology embryology, physiology, cell biology, biochemistry, genetics and immunology etc.

Individual cells are structural and functional unit of plants and animals. Since students are well acquainted with the structure of cells, therefore not discussed. A body consists of various types of cells, which form tissue. Tissues form larger functional units called organs. A collection of organs, which together subserve a particular function, forms the system. In this book structure of tissues and organs have been described in detail.

PREPARATIOn OF DEAD TISSUE

Following steps are under the way of preparation to study the tissues and organs with the help of light microscope.

Fixation–Fixation is to preserve the protoplasm with the least alteration in their nature.

Fixing Agent–Formaline and alcohol.

Procedure
1. Tissue is kept in 10% formaline for 24 hr.
2. Then rinse the tissue in running tap water for 5 minutes.
3. Dehydration in ascending order of alcohols. Tissue is put in alcohol as follows:
  1. 70% alcohol for 16 hr.
  2. 90% alcohol for 8 hr.
  3. 95% alcohol for 16 hr.
  4. 100% alcohol No. 1 for 2 - 4 hr.
  5. 100% alcohol No. 2 for 2 - 4 hr.
  6. 100% alochol No. 3 for 2 - 4 hr.
Clearing (dealcoholization)–Dealcoholization of tissue is done by putting the tissue in xylol.
1. Xylol No. 1 for 1 hr
2. Xylol No. 2 for 2 hr.
Embedding–After fixation and clearing, tissue is embedded in paraffin with the help of paraffin bath at 40°C for 1 hr and then block is made.
Sectioning–Thin slices of impregnated and bloked tissues are cut with the help of microtome. Thickness of ribbon is about 2 to 10μ.
Mounting on Slides–Sections are then mounted to a slide having fixative. Fixatives are gelatin adhesive or Mayer's albumin. Mounted slides are fixed in hot air oven at 60°C for 20 minutes.fm12
Staining–Staining is done in contrasting colours to bring out the structural details. Colouring ability of most dyes resides in either their acid or basic radicles.

Procedure–
1. Clearing–Wax is removed by clearing. Clearing is done by putting the slides in xylol.
  1. Xylol No. 1 for 2 - 5 minutes
  2. Xylol No. 2 for 2 - 5 minutes
2. Rehydration–Rehydration of tissue is essential for staining. Rehydration of tissue is done by putting the slides in descending strength of alcohol as follows:
  1. Absolute alcohol No 1 for 1 minute.
  2. Absolute alcohol No. 2 for 1 minute.
  3. 90% alcohol for 1 minute.
  4. 70% alcohol for 1 minute.
  5. 50% alcohol for 1 minute.
  6. Rinse the tissue in tap water for 5 minutes.
3. Staining–Put haemotoxylene over the slides for 5 to 10 minutes. sections are overstained. Wash it for 5 minutes in tap water.
4. Differentiation–Differentiation is done in 0.5 to 1 percent HCl in distilled water until tissue becomes red.
5. Bluing–Wash tissue in running tap water for 5 minutes or until tissue become blue.
6. Counterstaining–1 percent aqueous eosin stain is put over the slide for ½ to 1 minute and then washed in tap water.
Dehydration–Dehydration of tissue is done by putting the slides in ascending strength of alcohol as follws:
1. 50% alcohol for 1 minute.
2. 70% alcohol for 1 minute.
3. 90% alcohol–Rapid dipping and taking out the slide.
4. 100% alcohol No. 1 – Rapid dipping and taking out the slide.
5. 100% alcohol No. 2 – Rapid dipping and taking out the slide.
  
  Practically, I have observed that for dehydration, just dip the slide in alcohol and take it out; is sufficient.
Clearing–Clearing of tissue is done by putting the slide in xylol as follows:
1. Xylol No. 1 for 2 minutes.
2. Xylol No. 2 for 2 minutes.
Mounting–Put the gummy medium (DPX or Canada Wallsum) over the stained slide, over the DPX, cover slip is kept and left to dry then after drying it eventually hardens. Refractive index of DPX is same as the refractive index of glass, therefore, it does not hamper the vision of slide under light microscope. Now the stained slide is ready for study under the light microscope.

Chapter Notes