Download Chapter 1 Introduction

Chapter 1
Introduction
I. What’s histology?
II. Why we study it ?
III.
How to study it ?-Histological
methods.
I. What’s histology?
Histology (Greek words):
/histo-tissue
/logia-study of ,or knowledge of
So, histology means the knowledge of tissue, is a
branch of Anatomy.
Anatomy:
---gross anatomy
---microscopic anatomy
Structures related to function. So, exactly,
Histology is a science which study the
microstructure and the relationship between the
structure and function of human being.
Cell: smallest unit of structure and function of body
↓
tissue: group of cell+extracellular ground
substance
four basic tissue:
---epithelium
↓ ---connective tissue
---muscular tissue
---nervous tissue
organ: made up of tissue, have special shape,
structure and function
↓
system: organs Which have related function get
together.
II.What’s Embryology?
Embryology is a kind of science
which study the processes and the
regulations of the development of
human fetus.
III. How to study it- histological methods
---Development of histology deponds on the
development of technique.
---Histology studies the microstructures. So, we
should have the aid of microscope to study.
Several types of microscopes are available.
According to the light source used,
microscopes can be basally classified as:
light microscope(LM)
electron microscope(EM)
1. structure of Microscope
LM
---useful magnification: 1500X
---resolution:
0.2um
EM
800,000X
0.2nm
2. Preparation of tissue for LM
The most routine one is paraffin section stained
with hematoxylin and eosin(H&E)
The steps:
a. Obtaining th specimen: fresh, small pieces
( less than 5mm3)-tissue block
b. Fixation: fixatives: use formalin or Bouin’s to
preserve structural organisation
c. Dehydration: use ethyl alcohol to get rid of
water of tissue and cell
d. Clearing: use xylene to get rid of alcohol
*alcohol and xylene are embedding mediums
e. Embedding: firstly, heat the paraffin, make it
melt, then put tissue block into melted paraffin,
allow paraffin harden, the tissue block is
embedded in.
f.
Sectioning: use microtome to cut the tissue
into 3-8um thick sections, then monted them
on glass slides
g. H&E staining
---Hematoxylin: basic stain, combines with
acidic components, make them appear blue
colour- we call such components as
basophilic
---Eosin: acidic stain, combines with basic
components, make them appear pink colourwe
call
such
components
as
acidophilic(eosinophilic)
3. Preparation of tissue for EM
The steps are same to preparation for LM
a. tissue block: more small, less than 1mm3
b. plastic materials for embedding
c.
ultra-thin sections is about 30-50nm
thick( use ultramicrotome)
d. heavy metal salts- increase staining contrast
---lead citrate
---uranyl acatate
e. the beam of electron replace the light to
illuminate the tissue sections
Beam of electron illuminate the tissue
section, we use a screen to receive the
electron. In some areas, the beam of electron
is impeded by those tissue element which are
stained with heavy metal salts, so very few
electrons penetrate to excite the screen, such
areas appear dark, are described as electrondense areas. Unstained areas, by contrast,
appear light, we call them as electron-lucent
areas.
4. Histochemistry
1) General Histochemistry:
Combine histological methods with chemical
or biochemical methods, make some
compositions of tissue or cell become
insoluble, coloured or electron-dense,, to
show those chemical compositions of tissue
or cell in situ, such compositions includes
protein,amino acid, nucleic acid, lipid and
enzymes.
*Periodic acid schiff reaction(PAS reaction):
HIO4
schiff’s reagent(colourless)
Polysaccharides → aldehydes
→
magenta comples
Glycogen
oxidize
combine
(purple red coloured)
2)
immnohistochemistry: antigenantibody
3) in situ hybridization: nucleic acid:
DNA(desoxyribose
nucleic
acid)
RNA(ribose nucleic acid)