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Kharkov National
Medical University
Department of
Histology, Cytology and Embryology
Lecture 1. Introduction. Cytology
Histology – is the science that studies
microscopic structure and function of the
human organism, the organization of the
tissues and organs.
Cytology – is the science that study the
structure and functions of the cell.
Cytology
The cell is:
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
the smallest structural and functional
unit,
- the elementary level of organization of
the multicellular organisms.
-
- a self-regulating, self-regenerating
and self-governing biological system

cell possesses all features of the whole
organism, such as metabolism, growth,
irritability, movement, and others.
Types of cells in human body
Cells produce matrix:
Light and electron microscopy are 2 mane methods in histology
Levels of biological systems

Biomolecules

membranes

organelles
CELL
Membrane contents:
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1 – lipids
(hydrophilic head)
2 – lipids
(hydrophobic tails)
3 – proteins
4 – carbohydrates
(only outer cell
membrane)
Lipids may be:
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Phospholipids – triglycerides (polar)
Cholesterol (non-polar)
Phospholipids :
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Phosphate group (hydrophilic heads)
Glycerol
Fatty acids (hydrophobic tails)
Proteins may constitute
close to 50% of membrane
content
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function :
1- channels,
in the membranes
2- pumps,
3- receptors,
4- enzymes,
5- integrative,
6- structural
Membranes form:
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Outer cell membrane – cytolemma or
plasmalemma
Organelles
Vesicles
Nucleus - nuclear envelop
Structure of a typical cell
1.
Cell membrane
2.
Nucleus
3.
Cytoplasm
organelles
Cytosol =
matryx,
hialoplasm
inclusions
Cell junction

- consist of multiprotein complexes that
provide contact between neighbouring
cells or between a cell and the
extracellular matrix.
Where Cells contact -- Cell junction
G
1
2
Cell junction
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Communicating or
Gap junctions junction
Tight junction
Desmosomes
Tight junction
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present in different
types of epithelia
two layers of glycocalyx
are fused .
act as a barrier, that
prevents the movement
of molecules into the
intercellular spaces
G
Gap junction
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allow for direct
chemical
communication
between adjacent
cellular cytoplasm
through diffusion
without contact of the
extracellular fluid
numerous in muscle
tissue
Gap junction
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Consists of six connexin
proteins, interacting to
form a cylinder with a
pore in the centre connexon.
This protrudes across the
cell membrane, and when
two adjacent cell
connexons interact, they
Desmosome 

is the most common
type of junction
Provides cell
attachment
Inside the cell :

Cytoplasm and
nucleus
Inside the cell …
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Cytoplasm consists of:
Matrix (hialoplasm, cytozol)
Organelles
Inclusions
Inclusions
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Inclusions are
"nonliving"
components of the
cell.
They include granules
with secretions,
pigment granules,
lipid droplets, and
glycogen.
Organelles:
classification by structure
Membranous or
"membrane-bound"
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Non-membranous
Organelles:
classification by function
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General (present in
every cell, perform
general function)
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Special (in specialised
cell, perform special
function)
Rough (rough-surfaced) endoplasmic
reticulum
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is a membranous
network of sac-like
structures cisternae.
the cisternal space (or
lumen) is continuous
with the perinuclear
space but separate
from the cytosol.
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The surface of the
RER is studded with
ribosomes giving it a
"rough" appearance
(hence its name).
Function - synthesis
of proteins
Smooth(-surfaced) endoplasmic
reticulum, SER
SER consists of tubules that are located near the
cell periphery.
Function:
 It synthesizes lipids - phospholipids and steroids.
 It also carries out the metabolism of
carbohydrates (synthesis of glycogen,
gluconeogenesis ),
 drug detoxification, and steroid metabolism.
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Storage of Ca-ions (only in muscle cell)
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Golgi apparatus
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also known as the
Golgi complex, Golgi
body, or simply the
Golgi,
is an organelle found
in most eukaryotic
cells.
It was identified in
1897 by the Italian
physician Camillo
Golgi and named after
him in 1898.
Loks as a pack of
sacs.
Golgi apparatus

Golgi complex is
connected with
endoplasmic reticulum
Golgi apparatus
Functions.
1. synthesis of
substances,
which has begun in
endoplasmic reticulum
and is accomplished
in the Golgi complex.
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Golgi apparatus
Functions.
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2. formation of
compound
molecules –
glycoproteins,
lipoproteins.
Golgi apparatus
Functions.
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3. production of
lysosomes and
secretory vesicles.
Mitochondrion
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is a membraneenclosed organelle
found in most
eukaryotic cells.
Mitochondrion
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A mitochondrion
contains outer and
inner membranes
composed of
phospholipid bilayers
and proteins.
Folds of inner
membrane – cristae
Inside M. lie matryx
Mitochondrion
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Mitochondria provide
energy for various
cellular functions ,
Produce ATP
molecules
by Krebs cycle
Lysosome
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Lysosomes are round
vesicles that contain acid
hydrolase enzymes that
break down waste
materials and cellular
debris.
Lysosomal enzymes help
in digesting the materials
within phagosomes. They
can be described as the
stomach of the cell.
Lysosome Cycle
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lysosomes are formed
from Golgi complex
The nearly produced
lysosome is primary
lysosome
Lysosome Cycle
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primary lysosome
fuses with the
phagosome -secondary lysosome
or phagolysosome
part of undigesting
material may remain
within the cell as
residual bodies.
Non-membranous organelles:
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Microfilaments
Microtubules
Centrioles (Cell Center)
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Ribosomes
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The cytoskeleton
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- is made up of
three kinds of
protein filaments:
Actin filaments (also
called microfilaments)
Intermediate
filaments
Microtubules
Microfilaments, Microtubules
form “Skeleton” of the cell
Cell center
Centriole = 9 x 3
microtubules;
2 centrioles = cell center
= Β-tubulin
function -formation of
mitotic spindle
(mitosis, meiosis),
flagella, basal bodies
and cilia
Cell center
Nucleus
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Eukaryotes have nucleus
Nucleus is a membrane-limited structure:
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Nucleolemma nuclear envelope
Nucleoplasm
Nucleolus
Chromatin,
chromosomes
Nuclear envelope
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- Consists of two
membranes.
The outer layer is
continuous with
endoplasmic
reticulum.
The inner layer
provides attachment
to the ends of the
chromosomes.
Nuclear envelope
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There are gaps,
called nuclear
pores
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The nuclear pore
transports some
substances from
nucleus into
cytoplasm
Nucleolus
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Nucleolus is the
site very
amplificated
molecule of DNA.
It is the site of
active synthesis of
ribosomal RNA.
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In the nucleolus
RNA binds with
protein and forms
ribosomal subunits,
which leave the
nucleus via nuclear
pores to the
cytoplasm as
ribosomes.
Chromosome - DNA molecules
which contain genetic information
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DNA molecule is
coiled around the
histone core, which
consists of eight
gistone molecules.
Such particles,
consisting of gistone
core and DNA, are
called nucleosomes.
Chromatin
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is the combination of DNA and proteins that
make up the contents of the nucleus of a cell.
The primary functions of chromatin are 1) to
package DNA into a smaller volume to fit in the
cell, 2) to strengthen the DNA to allow mitosis,
3) to prevent DNA damage, and 4) to control
gene expression and DNA replication
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Sites where chromatin
fibrils are packed very
tightly together are
heterochromatin sites –
non-active.
there are less condensed
chromatin fibrils loops euchromatin sites active.
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Euchromatin predominates in metabolically active
nuclei,
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Heterochromatin predominates in metabolically
inactive nuclei
Chromosome is an organized
structure of DNA and protein found
in cells.
Cell Cycle
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The life of a somatic cell is a cyclic
process
It is called cell cycles
consists of two periods: interphase and
mitosis.
Interphase
Interphase is a period
between two divisions
of the cell.
Consists of 3 phases G1 , S , G2
In G1 phase:
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cell grows,
performs its
routine functions.
In G1 phase
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Nondividing cells complete period G1 by
growing old and death of the cell
Dividing cell – prepare for next phase
S- phase = synthesis phase
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DNA molecules are duplicated
each chromosome now consists of two
DNA molecules or two chromatids. At the
beginning of this phase, the chromosome
number is 2N and at the end, the
chromosome number is 4N.
G2 phase
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In this phase synthesis of proteins, which
are required for cell division, takes place.
After phase G2 mitosis always begins
G0 phase
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cell can leave the cycle in any phase, except
G2, and enter to so-called G0 phase (outside the
cycle). The cell that leaves the cycle is
considered as reserve stem cell.
Mitosis
is the process of somatic cells
division.
Mitosis consists of four phase:
prophase,
metaphase,
anaphase,
telophase.
Prophase
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Chromosomes
becomes more and
more coiled
become
recognisable.
the nuclear
membrane breaks
down and the
nucleoli disappear
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Two centrioles
separate and move to
opposite poles of the
cell.
Сentrioles produce a
number of
microtubules which
pass from one
centriole to other and
form a spindle of
division.
Metaphase
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- chromosomes
move to a position
midway between
the two centrioles
at the equator of
the cell and form
the equatorial plate
anaphase
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- the chromatids
separate and move
to opposite poles
of the cell
At the end of
anaphase
chromatids are
called
chromosomes.
Telophase
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- two daughter nuclei
are formed by
appearance of nuclear
membranes around
them.
The chromosomes
gradually elongate
and become
indistinct.
Nucleoli reappear.