2. Introduction to Histology
andHistological
techniques.
■Objectives:
At the end of the lecture you should be
able to:
o
o
1. Know the organization and components of the
human body and the principle tools used to study its
microscopic structures, i.e. the different techniques for
preparation and staining of tissue sections and
different types of microscopes.
2. Explain the significance of tissue culture
techniques to the study of live cell systems.
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3. THE CELL
■ At the end of the lecture you should be
able to:
o
o
1. Know the structure of the different
components of the cell at both light and electron
microscope levels and give their functional
significance.
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2. Correlate between the predominance of cell
organelle and the function of the cell.
4. Histology: is the study of the cells
and tissues.
Cytology: is the study of the
structure and function of the cell.
The cell: every cell consists of
cytoplasm surrounded by membrane
and contains nucleus. Suspended within
the cytoplasm; are the organelles and
inclusions.
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5. The cell is surrounded by a membrane and
contains: (I) Nucleus
(II) Cell organelles
(III) Cell inclusions
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7. The Nucleus
1. Nucleolus: is the center for the
synthesis of ribosomal RNA
2. Nuclear membrane (envelope):
- It surrounds the nucleus & is formed
of inner and outer membranes.
- The space between the two layers
is named perinuclear cisterna
- The nuclear pores are perforations in
the nuclear envelope.
3. Chromatin: is the genetic material of
the cell (DNA). It is formed of:
- Heterochromatin: inactive form
- Euchromatin: active form
4. Nucleoplasm
(Karoplasm):
Which contains
macromolecules and
nuclear particles
responsible for
maintenance of the cell
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8. (II) Cell organelles
o Organelles are
specialized parts of
living substance
within cells.
o Organelles are
divided into:
(A) Membranous
(B) Non membranous
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10. B) Non membranous organelles:
oCytoskeleton of the cell:
➢Microtubules
➢Filaments
oCentrioles
oRibosomes
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11. •
•
•
Cell Membrane
LM: Not visible
EM: It has
trilaminar
appearance = it
appears as 2
electron dense lines
and a clear space in
between.
Molecular
structure:
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12. ■
Cell Membrane Molecular Structure
The cell membrane consists mainly of lipid and protein and
other molecules.
1 . lipid is mainly phospholipid (bimolecular) lipids
present in the central part of the cell membrane.
Each lipid layer is formed of:
✵ Hydrophilic head: attached to water.
✵ Hydrophobic tail: no affinity to water.
2. Protein molecules: constitute about 60-70% of
membrane mass.
a. Peripheral proteins attached to the
heads.
b. Integral proteins throughout the
phospholipid
3.Other molecules:
A.
B.
Cholesterol
Carbohydrate: glycoprotein and glycolipid which form the cell coat
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(glycocalyx)
14. ■
■
■
■
■
Mitochondria
It is the main source of energy in
the cell.
They can divide by binary
division.
The inner membrane is highly
folded (cristae) and the outer
membrane is smooth.
The mitochondrial lumen is filled
with matrix, which contains
mitochondrial granules.
Function:
■
■
It is the powerhouse of the cell. It
contains enzymes of the Kreb’s
cycle.
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15. RER
SER
SER
■
Endoplasmic Reticulum
RER and SER
It is formed of anastomotic network of
tubules and vesicles.
There are two types:
1. Smooth endoplasmic reticulum
(SER)
■ Its lumen is continued with the lumen
of RER.
Function:
■
■
■
■
Steroid and lipid synthesis
Detoxification of drugs.
It may be involved in glycogen
synthesis.
Form sarcoplasmic reticulum in
skeletal muscle.
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16. RER
RER
Endoplasmic Reticulum
RER
2. Rough endoplasmic reticulum
(RER)
■
■
The outer membranes of these
saccules are richly studied with
ribosomes.
The cells rich in (RER) stains
deeply with basic dye
(basophilia) i.e. blue color.
Function:
■Protein synthesis and
modification
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The outer membranes of these saccules are
richly studied with ribosomes.
17. Golgi Apparatus
Golgi Apparatus
It is formed of a stack of
parallel flattened cisternae
or sacs, each cisternae has
2 faces:
❖
❖
Cis Golgi or forming face
(convex) towards nucleus.
Trans Golgi or mature
face (concave)towards
plasmalemma.
•
•
•
Transport vesicle.
Condensing vacuoles.
Secretory vesicle.
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18. ■
Golgi Apparatus Function
Function:
➢
➢
➢
It is concerned with secretory activity
of the cell.
Modification and sorting of proteins
manufactured on RER.
Has a role in membrane
biosynthesis.
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21. •
•
•
Lysosomes
They have different sizes and shapes.
They have hydrolytic enzymes.
Function:
Digestion of macromolecules, microorganisms, cellular debris and
excessive organelles
• Types:
1- Primary lysosomes
digested material.
2- Secondary lysosomes:
recently formed and don`t contain
❑
❑
❑
phagosome
auto phagic vacuole
pinocytotic vesicle
3- Residual body lysosome that digested materials.
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23. Peroxisomes
Perixosomes: (Microbodies = spherical bodies)
• They contain oxidative enzymes that are responsible for
break down of H2O2 (Hydrogen peroxide), which is a toxic
substance.
Endosomes
•They are system of tubules and vesicles
•Prepare contents for the destruction by
lysosomes
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25. (B) Non- Membranous organelles:
1 . Cytoskeleton:
•They maintain the shape of the cell.
•They include:
a.Microtubules formed of tubulin
b.Filaments = microfilaments.
-Thick filaments (Myosin)
-Intermediate filaments (Tonofilament)
- Thin filament (Actin)
• Function:
-Shape and movement of the cell, cilia,
flagella -Transport of vesicles and
chromosomes
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27. 2- Centriole: is involved in cell division.
3. Ribosomes:
•They are granules consist of 2 subunits: large and small.
•They are attached to (RER) by their large subunit.
•There are two types of ribosomes:
➢ Attached ribosomes:
Are attached to RER by their large subunits.
➢ Free ribosomes:
They circulate freely in the cytoplasm.
Polysomes: are ribosomes forming circled
strings •Functions:
-Attached ribosomes are responsible for protein secretion
to outside the cells (proteins for export).
-Free ribosomes are responsible for protein synthesis
inside the cells.
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29. (III) Cell Inclusions
■ These are the non- living structures of the cell:
■ Pigments:
■ Melanin
■ Lipofuscin
■ Haemosidrin
■ Lipid = Fat droplets.
■ Glycogen : stored in liver cell and muscle.
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