‫بسم هللا الرحمن الرحيم‬
INTRODUCTION TO
HISTOLOGY
HISTOLOGY
(MICROSCOPIC ANATOMY)
Definition.
Basic Histological Techniques
• (A) Light Microscopy:
1- Fixation: e.g. Formalin.
2- Dehydration: Ethanol.
3- Clearing: e.g. Xylene.
4- Embedding: e.g. Paraffin.
5- Sectioning: Microtome.
6- Staining:
e.g. H&E (Hematoxylin& eosin).
Acidophilic and basophilic structures.
e.g. Metachromatic staining (Toluidine blue).
Microtome
Light Microscope (L/M)
• 1- Illumination.
• 2- Magnification.
• 3- Resolution.
N.B. Resolving power ( It is the least
distance between 2 particles at
which they will appear separated).
R.P. for L/M is 250 nm
Light microscope
(B) Electron microscopy:
1-Transmission E/M: Resolving power 0.2 nm.
* Electron-dense structure
**Electron-lucent structure
2-Scanning E/M: Resolving power 10 nm.
Transmission Electron Microscope
Scanning Electron microscope
THE CELL
THE CELL NUCLEUS
(INTERPHASE NUCLEUS)
Shape of nuclei
Dark Nucleus
(Deeply-stained nucleus)
Vesicular(open face) Nucleus
CELL NUCLEUS
(Interphase Nucleus)
L/M:
Appearance (Type):
- Light nucleus (vesicular) (open face)
- Dark nucleus (deeply-stained) (dense Nucleus)
Number: 1, 2, or more.
Position:
Central, eccentric, peripheral, basal.
Cell Nucleus
• L/M:
Size:
Small, medium, large
( Nucleus/cell ratio)
Shape:
e.g. Rounded, oval, rod-shaped.
Nucleus (E/M diagram)
Nucleus (Electron Micrograph)
PRACTICAL
Nuclear pores
Cell Nucleus
(Interphase nucleus)
E/M:
(1) Nuclear envelope
Inner nuclear membrane.
Outer "
"
.
Nuclear pores.
Nuclear pore complex.
Perinuclear cisterna.
Nuclear lamina.
N.B.Rough Endoplasmic reticula.
(2) Chromatin: ( Classification ):
Metabolic activity:
a- Euchromatin(Extended chromatin)
b- Heterochromatin(Condensed chrom.)
According to Position:
a- Peripheral chromatin.
b- Nucleolus-associated chromatin.
c- Chromatin islands.
According to
Nucleolus (E/M)
(3) Nucleolus:
L/M: 1-5 basophilic bodies
E/M: 1- Pale-staining fibrillar center:
Nucleolar organizer DNA**
+ Inactive DNA
N.B. ** are found in the tips
of chromosomes 13,14,15,21&22
with genes that encode rRNA.
2- Pars fibrosa:
containing rRNA (nRNA)
being transcribed.
Nucleolus (cont.):
3- Pars granulosa:
maturing ribosomal subunits are assembled.
4- Nucleolar matrix:
a network of fibers active in nucleolar organization.
N.B. Nucleolus is a non-membranous structure.
Function of nucleolus: rRNA synthesis.
NUCLEOPLASM
•
•
•
•
1- Nuclear matrix.
2- Ribonucleoprotein.
3- Interchromatin granules.
4- Perichromatin granules.
APOPTOSIS
Definition:
Genetic programmed cell death.
Mechanism:
Caspases: enzymes coded by highly conserved genes.
Caspases are activated by cytokines e.g. TNF.
This triggers a cascade of caspases.
Degradation of chromosomes,
Nuclear lamins & cytoskeletal proteins.
The entire cell becomes fragmented.
The cell fragments are then phagocytosed by macrophages.
PRACTICAL SESSION
Electron Micrographs
Nucleus (Electron Micrograph)
Nucleolus (E/M)
Nuclear pores
BEST WISHES
CYTOPLASM
(1) Organelles.
(2) Cytoskeleton.
(3) Inclusions.
(4) Cytosol.
Cytoplasmic organelles
1- Cell Membrane.
2- Ribosomes.
3- Endoplasmic Reticulum.
4- Golgi Apparatus.
5- Lysosomes.
6- Peroxisomes.
7- Proteasomes.
8- Mitochondria
9- Annulate lamella.
Cytoskeleton
1- Thin Filaments.
2- Intermediate Filaments.
3- Microtubules.
Cell Surface Specializations
1- Microvilli.
2- Cilia.
Cytoplasmic Inclusions
1234-
Glycogen.
Lipids.
Pigments.
Crystals.
Cell Membrane
(Plasmalemma)
CELL MEMBRANE &
GLYCOCALYX
ENDOSOMES
MITOCHONDRIA
ENDOPLASMIC RETICULUM
ROUGH ER
RER & SECRETORY GRANULES
POLYSOMES
(POLYRIBOSOMES)
GOLGI APPARATUS
CILIA
CILIA & CENTRIOLES
Glycogen granules in hepatocyte