Transcript 1-Introduction to histology

Histology and
Embryology
组织学与胚胎学
Department of Histology and embryology
Three Gorges University, Yichang, China
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.

It is the bases of other subject in medicine.
It intertwines the disciplines of cell biology,
biochemistry, physiology, and as appropriate,
pathology. Students will recognize the
importance of this subject as they refer to the
text later in your careers.
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 5 cubic milimeter(mm3))-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 mounted them
on glass slides
g. H&E staining
---Hematoxylin: basic stain, combines with
acidic components, make them appear blue
color- we call such components as basophilic
---Eosin: acidic stain, combines with basic
components, make them appear pink colorwe
call
such
components
as
acidophilic(eosinophilic)
observing
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 acetate
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, colored 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):
schiff’s reagent (colorless)
Polysaccharides → aldehydes
→ magenta complexes
Glycogen
oxidize
combine
(purple red colored)
2)
immnohistochemistry: antigenantibody
3) in situ hybridization: nucleic
DNA(desoxyribose
nucleic
RNA(ribose nucleic acid)
acid:
acid)