Transcript Document

HISTOLOGY &
EMBRYOLOGY
Teaching PPT
Dept. of Anat., Hist. & Embry.
School of Medicine
Xi’an Jiaotong University
HISTOLOGY
Qiu Shudong
INTRODUCTION
Definition: A science: study normal microstructure & its related function of human body.
4 structural levels:
Cell: the smallest structural & functional unit.
Tissue: groups of cells (similar in morphology
or related in function)＋intercellular materials
4 types of fundamental tissue
epithelium
connective tissue
muscular tissue
nervous tissue
Organs: organizations of various
kinds of tissues in particular ways &
perform a specific function.
System: formed by several functionrelated organs which together perform a
continuous physiological function.
For example: digestive system
Why to study histology ?
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To complete the knowledge of human body’s
structures----from gross to microscopic
Be able to understand how the different tissues
function----the basis of physiology
Can find the diseases only after the normal is
known----the basis of pathology
It is related to some modern science fields: cell
apoptosis, cell recognition, implantation of
embryo stem cells, eugenics and etc.
It is also a foundation of clinic sciences—for a
good doctor needed in futrue
Unit used in microscope
1μm=1/1000 mm
1 n m=1/1000μm
Maximum resolution
Light microscope: 0.2μm
Transmission electron microscope: 0.2nm
Scanning electron microscope: 5nm
Investigative methods of histology
I. Light
microscopy
1. Tissue preparation
A. paraffin section preparation
 Specimen: as fresh as possible
 Fixation: fixative: formalin solution;
purpose: to preserve the structural
organisation
l Dehydration: replace the water in the tissue
by alcohol
 Clearing: replace the alcohol by xylene
 Embedding: replace the xylene w/ melted
paraffin
 Sectioning & mounting
B. Frozen section:
Better for preserving chemical components
(e.g. enzymes)
Freezing→cryotomy→staining
C. the others:
Smear preparations:
for blood etc;
Grind preparations:
for bone
2. Staining
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Purpose: To make tissue section pigment
for observation.
 H-E Staining:
Hematoxylin: basic dye, purple-blue
Eosin: acid dye, pink color
Basophilic: components bonded by basic
dye (H); pruple-blue（nuclear chromatin
& basophilic substance in cytoplasm）
Acidophilic: components bonded by acidic
dye (E); pink (cytoplasm & collagenous fiber)
Neutrophilic: do not stain w/ both basic and
acid dyes
Metachromasia: a dye stains tissue a
different color from that of dye solution, e.g.
toluidine blue stains mast cells in purple color
Special staining:
Argyrophilia
Fluorescent staining
Silver staining of
the neuron and
the bile canaliculi
HO (Hoechst
33258)-PI staining
shows the
apoptosis in human
HL-60 cells
II. Electron Microscopy
1. Transmission Electron Microscope (TEM)
 Using a beam of electrons (short wave-lengths)
instead of visible light.
 Section preparation:
similar to those for L.M mainly,
plastic instead of paraffin,
50-70nm thick,
heavy metal salts instead of HE.
 Resolution: 0.1-0.5nm (0.2nm)
 Ultrastructrue: The structure in EM
 Electron-dense / electron-lucent
Transmission Electron Microscope
Diagrams of TEM
2. Scanning Electron Microscope (SEM)
Sowing the 3 dimensional surface
Architecture of cells and tissues
Resolution: 5nm
III. Histochemistry & Cytochemistry
Reveal the chemical composition in
situ (e.g. proteins, a.a., nucleic acid,
lipids, enzymes etc.) w/ chemical,
biochemical methods.
The product of chemical reaction
should be insoluble / colored /
electron- scattering, & be seen in LM
or EM
For instance:
 PAS(Periodic Acid
Schiff) reaction:
for manifesting polysaccharide and
proteoglycan (e.g. glycogen).
polysaccharide + HIO4
(hydroxyl group)
(oxidise)
Aldehyde group + Shiff’s reagent
(colorless)
Purplish red depositor
PAS reaction in the hepatocytes
Immunocytochemistry
Based on antigen binds to specific antibody.
Tissue section w/ Antigen + labelled antibody
labelled Ag-Ab complex
Fluorescein
labelling
enzyme
labelling
colloidal gold
labelling
NOS & GnRH positive Neurons
in hypothalamus of rat
NOS positive neuron in
hypothalamus of rat
m-ATPase activity in skeletal muscles
IV. tissue culture
V. isotopic tracing
VI. in situ hybridization (ISH)
—nucleic acid molecular hybridization
Use nucleotide probe to check target
fragment of intracellular DNA or mRNA in
situ, in order to study the gene expression.
Expression of PSA and PSAmRNA in
human prostate (histochemistry & ISH)
The method in learning histology
 Combination of
the 2 dimentional structure
with 3 dimentional
Combination
of the theory with
practice
Combination
of the structure
with function
Concern
the dynamic change