ThinPrep ® General Cytology Lecture Series Cerebrospinal Fluid Cytology.
2- Cytology
description
Transcript of 2- Cytology
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CYTOLOGYBY
Dr. TAREK ATIA
Histology and Cell Biology
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Course of Histology
- Cytology: Cell, Nucleus, DNA, and
Chromosomes.
- Tissues: 4 basic tissues including;
Epithelium, Connective (Cartilage, Bone,
Blood), Muscular, and Nervous tissues.
- Body systems and different Organs.
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Cytology
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- Any cell consists of two main compartments:
- The Nucleus and the Cytoplasm.
- The cytoplasm; includes membranous and
non-membranous organelles.
- Membranous organelles such as; Cell
membrane, RER, SER, Golgi, Lysosomes,
Endosomes, Mitochondria,…….
- Non-membranous organelles such as,
Ribosomes, Centrioles, Microtubules,
Glycogen inclusions,,…..
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Cell membrane
- Maintain the structural integrity of the cell.
- Control movement of substances in and out
the cell.
- Regulate cell – cell interaction.
- Act as interface between the cytoplasm and
the external environment.
Recognition via receptors, antigens,…. -
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Cell membrane
- Cell membrane is not visible by the light
microscope, seen only by E/M.
- It is 7.5nm thick, and appears as a
trilaminar structure of two thin, dense
lines, and a light line in between.
-The entire structure is called a
unit membrane.
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Cell membrane
- The inner cytoplasmic dense line is its
inner leaflet, and its outer dense line
is the outer leaflet.
- Each leaflet is composed of a single
layer of phospholipids and associated
proteins.
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- Each phospholipid molecule is composed
of a polar hydrophilic head (at the
surface) and two long non-polar
hydrophobic fatty acyl tail (toward the
center).
- The polar head is composed of glycerol,
to which other molecules are attached.
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- The protein components of the cell
membrane either span the entire lipid
bilayer (integral proteins) or attached to
the cytoplasmic aspect of the lipid bilayer
(peripheral proteins).
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- The integral or trans-membrane
proteins form channels proteins (ion
channels) and carrier proteins that
facilitate passage of specific ions and
molecules across the cell membrane.
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P-Face
E-Face
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Membrane transport protein
- The hydrophobic components of the
plasma membrane limit or prevent
movement of polar molecules across it.
- The presence and activity of trans
membrane proteins will facilitate the
transfer of these hydrophilic molecules
across this barrier.
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-These transmembrane proteins form :
- Channel proteins:
- Carrier proteins:
Membrane transport protein
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Function of cell membrane
1- It maintains and preserves the integrity of the
cell.
2- It permits the movement of substances in and
out the cell by:-
A- Passive diffusion of simple substances as
water and some ions.
B- Facilitated diffusion: some substances as
glucose and amino acids can pass through it
with the help of carrier, but not need energy.
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C- Active transport: some substances can pass
through it against diffusion gradient, and
required energy.
D- Selective transport: depends on the presence
of receptors on the surface of cell
membrane to select and determine the
substances to enter the cell.
3- Phagocytosis
4- Pinocytosis
5- Exocytosis
6- Regulate the cell to cell interaction by special
type of cell junctions.
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Endocytosis
The process by which a cell ingests
macromolecule, particulate matter,
and other substances from the
extra-cellular space is referred as:
ENDOCYTOSIS.
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- Then, endocytosed material is engulfed in a
vesicle.
- If the vesicle is large (>250 nm in diameter): the
method is called phagocytosis (cell eating), and
a vesicle is called a phagosome.
- If the vesicle is small (<150 nm in diameter): the
method is called pinocytosis (cell drinking),
and a vesicle is called a pinocytotic vesicle.
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- Phagocytosis; the process of engulfing large
particles, or even cells by phagocytic cells
such as monocytes, neutrophils,
macrophages.
- Membrane trafficking; the cycle of
membrane shuffling during exocytosis
and endocytosis (membrane recycling).
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Receptors mediated endocytosis
- Many cells specialize in pinocytosis of
specific macro- or micro-molecules.
- The most efficient form of capturing these
substances depends on the presence of
receptors proteins (cargo protein) in the
cell membrane.
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Cargo proteins are
trans-membrane
proteins associated
with a particular
macro-molecules
(ligand) extracellulary,
and with a clathrin
coat intracellular.
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Mitochondria
- They are flexible, rod-shape organelles;
with diameter of 0.5 girth and ~7.0μ
length.
- Their number are variable in human cells;
e.g. they are abundant in hepatocytes
(~2000) and muscles.
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- Mitochondria are self replicating and
possess their own DNA, and perform
oxidative phosphorylation and lipid
synthesis. -
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Mitochondria considered as
the power house of the
cell.
They also control calcium level within the
cytoplasm.
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- Each mitochondrion possesses an smooth
outer membrane and folded inner
membrane (Cristae) with a narrow
space (10 – 20nm) between them is called
inter-membrane space.
-The space enclosing cristae is called inter-
crystals space or matrix space.
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- Cristae increase the surface area of the
inner membrane for ATP synthase
and the respiratory chain; and also
their number are related directly to
the energy requirement of the cell.
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- The outer mitochondrial membrane
possesses a large number of porins
(Multipass trans-membrane proteins).
- Porins form large aqueous channels
through which water soluble
molecules can pass.
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- The outer membrane is relatively
permeable to small molecules, so the
contents of the inter-membrane space
resemble the cytosol.
- Other proteins located on the outer
membrane are responsible for the
formation of mitochondrial lipids.
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- The inner mitochondrial membrane is
richly endowed with phospholipids
(Cardiolipin) that makes it permeable
to ions, electrons and protons.
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- In certain regions, the outer and the inner
membranes contact each other; the contact
site (composed of carrier protein) acts as
channels for proteins and small molecules
to enter or leave the matrix space.
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- The inner and outer membranes possess
receptor molecules that recognize the
transported macromolecules and the
cytosolic carrier molecules and
chaperones responsible for their delivery.
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- The inner membrane display a large
number of protein complexes such as ATP
synthase and Respiratory chains, so
mitochondria can be regarded as the
power house of the cell .
- Each respiratory chain composed of three
respiratory enzymes : NADH
dehydrogenase, Cytochrome b-c1 and
Cytochrome oxidase complexes.
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- These enzyme complexes form electron
transport chains that are responsible for
passage of electrons along this chain and act
as proton pumps that transport H+ from
the matrix into the inter-membrane space
that provide energy for ATP-generating
action of ATP synthase.
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- The matrix space is filled with dense
composed of 50% protein, mainly
enzymes responsible for degradation of
fatty acids and pyruvate to the
metabolic intermediate acetyl CoA and
the subsequent oxidation of this
intermediate in the tricarboxylic acid
(Krebs) cycle.
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- The matrix space contain also
mitochondrial ribosomes, mRNA,
tRNA, and dense spherical matrix
granules.
- Moreover, matrix contain the double-
stranded circular DNA (cDNA) and
enzymes necessary for expression of
the mitochondrial genome.
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- The mitochondrial cDNA contains
information for the formation of only
13 mitochondrial proteins, 16S and
12S rRNA, genes for 22 tRNAs.
- Therefore, most encodes necessary for
the formation and functioning of
mitochondria are located in the
nuclear genome.
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Protein Synthetic and Packaging
Machinery of the Cell
The protein synthetic machinery of the
cell composed of:-
Ribosomes, and polyribosomes
Endoplasmic reticulum
Golgi apparatus
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Ribosomes
- They are small (12nm wide and 25nm
long), non-membranous particles
composed of protein and ribosomal
RNA.
- Each ribosome is composed of large
subunit and small subunit.
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- They are assembled in the nucleolus
and released in the cytoplasm as
separate entities.
- Small subunit is composed of 33
proteins and 18S rRNA, but the large
subunit is composed of 49 proteins
and 3 rRNA.
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- The small subunit has a site for binding
mRNA, a P-site to bind to peptidyl
tRNA, and an A-site for binding
aminoacyl tRNAs.
- The small and large subunits are present
in the cytoplasm individually, and do not
form ribosomes until protein synthesis
begins.
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Rough endoplasmic reticulum and Polyribosomes
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Endoplasmic Reticulum (ER)
- It is the largest membranous system in the
cell.
- It is a system of interconnection tubules
and vesicles whose lumen is referred as
cistern.
- ER has 2 types; smooth and rough ER.
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- Their Functions are:-
- Manufacture of all membranes of the
cell.
- Protein synthesis and modification.
- Lipid and steroid synthesis.
- Detoxification of certain toxic
compounds.
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Smooth Endoplasmic Reticulum (SER)
- SER is a system of anatomising tubules
and flattened membrane-bound
vesicles.
- The lumen of SER is assumed to be
continuous with that of RER.
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- They are abundant in cells that active
in synthesis of steroids, cholesterol,
triglycerides, and also in cells that
are functioning in detoxification.
- Their surface is not attached to
ribosomes, and so, it is called smooth.
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Rough Endoplasmic Reticulum (RER)
- Their membranes possess integral proteins
that function in recognizing and binding
ribosomes to their surfaces and maintain
their flattened shape.
- RER participates in the synthesis of all
proteins that are packaged and delivered
to the plasma membrane.
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- RER performs post-translational
modification of these proteins.
- RER also manufactures lipid and
integral proteins of the cell membrane.
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The cisterna of
RER are
continuous with
the peri-nuclear
cisterna (the
space between
the inner and the
outer nuclear
membrane).
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Golgi complex
- Proteins manufactured in the RER go to Goli
apparatus for post-translational modification
and packaging.
- Golgi is composed of one or more series of
flattened, slightly curved membrane-bound
cisternae.
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- Each Golgi stack has three levels of
cisternae:- the cis-face, the medial-face,
and the trans-face, and then smooth or
coated vesicles.
- The cis-face is convex in shape and present
closes to the RER.
- The newly formed proteins from RER inter
first to the cis-face.
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- The trans-face is concave in shape and
is located at the distal part of the
Golgi apparatus, where the modified
proteins is ready to be packaged and
transport.
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There are another two compartments, one
associated with the cis-face and the other with
trans-face:
- The endoplasmic reticulum/Golgi intermediate
compartment (ERGIC), which is known as
tubulo-vesicular complex: located between
RER and cis-face Golgi.
- The trans-Golgi network (TGN): located at the
distal side of Golgi apparatus.
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Lysosomes
- Lysosomes are small rounded or
polymorphic in shape, with a diameter of
0.3 – 0.8μ.
- Lysosomes have an acidic pH, and contain
hydrolytic enzymes (~ 40 different types
of acid hydrolases).
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- Lysosomal membranes contain proton
pumps that transport H+ ions into the
lysosomes to maintain its luminal pH at
5.0.
- Lysosomes help in digesting
macromolecules, phagocytosed micro-
organisms, cellular debris, cells, and
senescent organelles such as
mitochondria & RER.
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- Lysosomes receive their hydrolytic
enzymes and membranes from the
Trans-Golgi Network that arrive in
different clathrin coated vesicles.
- The vesicles loss their clathrin coat shortly
after formation, and fused with late
endosomes.
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Substances subjected for degradation within
lysosomes pass through 3 ways:-
1 - Phagosomes either join lysosomes or late
endosomes. The hydrolytic enzymes digest
most the contents of phagosomes except
lipid which resist complete digestion and
changed into residual body.
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2 - Pinocytotic vesicles.
3 - Autophagosomes: Organelles that no
longer required by the cell become
surrounded by elements of SER, and
then enclosed in vesicles called
autophagosomes.
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Endosomes
- Endosomes are divided into early and late
compartments:
- Early endosomes are situated near the
periphery of the cell.
- Late endosomes are situated deeper in the
cytoplasm.
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Peroxisomes
- They are small (0.2 – 1.0 μ) spherical or ovoid
membranous organelles that present in almost
all animal cells and function in catabolism long
chain fatty acids (Beta oxidation) forming acyle
coenzyme A (CoA) and H2O2.
- Peroxisomes (microbodies) are self replicating
organelles (can divide) that contain more than
40 oxidative enzymes (urate oxidase; catalase;D-
amino acid oxidase).
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Proteasomes
- Proteasomes are small organelles composed
of protein complex that are responsible for
proteolysis of mal-formed and ubiquitin
tagged protein.
- The process of cytosolic proteolysis is
controlled by the cell, and it requires that
the protein be recognized as a potential
candidate for degradation.
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Cell Inclusions
- Thy are non-living components of the cell that do
not possess metabolic activity and are not
bounded by membranes.
- The most common inclusions are:-
1- Stored food:
: abundant in liver and muscle cellsGlycogen-a
; stored mainly in adipocytes, Lipid droplets-b
and present also in other cells.
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: could be endogenous or exogenous.Pigments-3
a- Exogenous pigments as carotene, carbon,
and dust.
b- Endogenous pigments such as; Hemoglobin,
Melanin, lipofuscin or lipochrom.
: are not commonly seen. Present in Crystals-4
Sertoli cells as (Crystals of Charcot-Bottcher)
and in interstitial cells as (Crystals of Reinke).
-
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Cytoskeleton
- They are meshwork of protein filaments
responsible for maintenance of cellular
morphology, and participate in cellular
motion.
- The cytoskeleton has three major components;
1- Thin filaments
2- Intermediate filaments
3- Microtubules
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1- Thin Filaments (Actin)
- The actin filaments are composed of 2 chains
of G-actin (globular actin) subunits coiled
around each other to form F-actin (filamentous
proteins).
- There are 3 types of actin filaments:
α-actin of muscle cells reacting with myocin.
β-actin in non-muscle cells.
Ƴ-actin in non-muscle cells.
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- In non-muscle cells actin filaments form 3
types of bundles of variable length and
function:
- Contractile bundles
- Gel-like networks
- Parallel bundles
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2- Intermediate filaments
- The intermediate filaments and their associated proteins perform the following:
- Provide structure support of the cell
- Establish a 3-dimensional structural framework for the cell.
- Anchor the nucleus in place.
- Provide connection between the cell membrane and the cytoskeleton.
- Maintenance of the nuclear envelop and its subsequent changes that takes place in mitosis
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3- Microtubules
- Microtubules are long, strait, rigid, hollow-
like cylindrical structures act as
intracellular pathways.
- The centrosome is consider to be the micro-
tubule-organizing center (MTOC) of the
cell from which most of the cell's
microtubules emanate.
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- Their main functions of microtubules are:
- Provide rigidity and maintain cell shape.
- Regulate intracellular movement of vesicles
and organelles.
- Established intracellular compartments.
- Provide the capability of ciliary motion.
- Microtubule-associated proteins:
Motor proteins that assist in translocation of
organelles and vesicles inside the cell, such as
Dynein and Kinesin.
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Centromere: Centrioles
- Centromere is present in all dividing cells near
the nucleus, and is composed of 2 perpendicular
centriols.
- Centriol is cylindrical in shape.
- The centriols duplicated during cell division
- Each centriol composed of nine sets of triplet
microtubules.
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Structure of microtubules organizing center (MTOC).
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Cilia and Flagella
- Cilia (cilium) are hair-like motile processes
extend from the free surface of ciliated cells.
- Flagellated cells (sperm) has only one flagellum.
- Both cilium and flagellum composed of the same
core organization, which is called axoneme.
- The axoneme is formed of nine pairs (doublets)
and 2 central (singlet) microtubules.
- At the base of cilia or flagella there is a basal
body, which is similar to centriol in structure.
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Cilia
microvilli
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Stereocillum
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Cell activities
- Cell division.
- Endocytosis
- Exocytosis
- Cell death:
- Necrosis
- Apoptosis
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Nucleus
- All human cells contain nucleus except the
mature red blood corpuscles.
Normally each cell contains a single :Number-
nucleus, but sometimes contains two as liver
cells, or more (multinucleated) as skeletal
muscle cells, and osteoclasts.
: Nucleus could be spherical, oval, Shape-
flattened, or lobulated.
: Nucleus could be central, basal or Position-
peripheral.
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Structure of the nucleus
- Nucleus composed of:
- Nuclear membrane (Envelop)
- Chromatin
- Nucleolus
- Nucleoplasm
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1- Nuclear Envelop
- Nuclear envelop is composed of two
parallel unit membranes; the outer and
the inner membranes separated from
each other by a 10-30 nm space called
perinuclear cisterna.
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- The two membranes fuse with each
other at certain regions known as
nuclear pores that permit
communication between cytoplasm
and nucleus .
- The nuclear pores is surrounded by a
non-membranous structure called
pore complex.
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2- Chromatin
- Chromatin is a complex structure
formed of DNA associated with
histone and non-histone proteins.
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- Depending on its transcriptional
activity chromatin can be divided into:-
- Euchromatin; not condensed, stained
lightly basophilic, gene rich, and early
transcript.
- Heterochromatin; condensed, stained
deeply basophilic, gene poor, and late
transcript.
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3- Nucleolus
- Nucleolus is a non-membranous deeply
stained structure located in the nucleus.
- It present during interphase and
disappear during cell division.
- It contain ribosomal RNA, some proteins
and small amount of DNA.
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- Structure of the nucleolus: It is formed of four
areas
- Pale staining Fibrillar center containing
inactive DNA, and nucleolar organizing
regions (tips of acrocentric chromosomes).
- Pars Fibrosa containing nucleoluar RNAs
- Pars Granulosa in which mature ribosomal
subunits are assembled
- Nucleolar Matrix: a network of fibers active
in nuclear organization.
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4- Nucleoplasm
• Nucleoplasm composed of the following
1- Interchromatin Granules: They are
located in clusters scattered throughout
the nucleus among the chromatin
material.
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2- Perichromatin Granules: They are
located at margins of heterochromatin,
and are composed of:
- Heterogeneous nuclear ribonucleo-
proteins
- Small nuclear riboprotein particles
3- Nuclear Matrix: Contain DNA, RNA,
Proteins, and nuclear phosphate.
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