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Lecture 1
General med_2nd semester
Introduction. The object and significance of
histology. Short history of the histology. Brno
histological and embryological school. Methods
used to study of cells and tissues
Cytology: The cell - definition and general
characteristics. Cell membrane, cell surfaces and
intercellular junctions. Cell nucleus - its structure
and function. Chromosomes
http://www.med.muni.cz/histol/histolc.html
lectures +
practicals
(Prof. Dr. Dr. S. Čech, DrSc.)
http://www.med.muni.cz/histol/
histolc.html
lectures
(Prof. Dr. Dr. S. Čech, DrSc.)
+
practicals
Textbooks
recommended to
study:
2008
ISBN: 978-1-4160-3706-4
The Developing Human, 8th Edition - Clinically Oriented Embryology With
STUDENT CONSULT Online Access
By Keith L. Moore, BA, MSc, PhD, FIAC, FRSM and T. V. N. Persaud, MD, PhD, DSc,
FRC Path(Lond)
536 pages 1805 ills
Trim size 8 1/2 X 10 7/8 in
$69.95, Softcover
2008
ISBN: 978-1-4160-3705-7
Before We Are Born,
7th Edition - Essentials
of Embryology and Birth Defects
With STUDENT CONSULT Online
Access
By Keith L. Moore, BA, MSc,
PhD, FIAC, FRSM and T. V. N.
Persaud, MD, PhD, DSc, FRC
Path(Lond)
368 pages 1308 ills
($54.95, Softcover)
UKB, Kamenice 5, Building A9 A, 625 00 Brno
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Mobile: 608 877 315
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The object and significance of
histology and embryology
Short history of the branch
Brno histological and embryological
school
Methods used to study of cells and
tissues
histology and embryology are fundamental branches on medical
schools
origin of the term of histology
greek histos meaning "tissue„ + logos meaning "the study off" (knowledge or science); the term was
primarily used in strict sense of the word as a denotation for study of microscopic parameters of animal and
plant cells and tissues
recently, histology = as a branch of science that treats microscopic and
submicroscopic structure (organization) of animal or plant bodies
on medical schools - it deals with microscopic and submicroscopic structure of the human body
animal and plant organisms consist of organs, organs of one or more tissues and tissues are
composed of cells that are considered for elementary units of the living substance
in accordance with 3 mentioned organizational levels – cell, tissue, and organ – histology
divides into 3 sections:
cytology - deals with microscopic and ultrastructural organization of cells
histology proper (or histology in strict sense of this word) - describes light microscopic structure
and function of tissues
microscopic anatomy - a section of branch studying microscopic and fine structure of individual
organs
major interdisciplinary branches:
histochemistry, histophysiology, pathological histology, and electron microscopy
Importance of histology:
a basic subject, on which pathology a pathophysiology are built
is used in diagnosis of diseases (department of pathology)
used in farmaceutical industry (for testing drugs and artificial materials used
for substitutions of natural organs)
in control of food quality
embryology – its aim and orientation are quite different
the term - of 2 greek words en = in, bryein = to swell
embryology deals with study of individual development
of multicellular organisms
individual development /ontogenetic development = ontogeny/ involves
the period from fertilization of the ovum to the death of respective
individual
the main reason why histology and embryology are teached together is that
all multicellular organisms begin their existence as single cells =
generative cells or gametes
model of simultaneous teaching of both disciplines (H + E) is often in
countries of middle Europe
Short history of histology
development of histology to a separate branch of science was closely associated
with 3 preconditions:
the construction of the light microscope
the proclamation of the cell theory
the improving of methods of tissue processing
a) beginning of microscopic examinations dates from the end of sixteenth century
the first simple microscope was constructed by father Hans and his son Zacharias
Jansen (1590)
R. Hooke and M. Malpighi have employed microscope in studies of structural
features of various organisms (the first half of the 17th century)
A. Leeuvenhook (between 1673-1716) constructed and used composed
microscope and published a series of observation upon protozoa, bacteria, muscle,
nerve and other structures (the second half of the 17th century)
a great boom of light microscopy comes in the 19th century
when cell nucleus and basic cell organelles (e.g. centrioles, mitochondria, apparatus
of Golgi) have been discovered
b) the proclamation of the cell theory - this idea says that the all animal
as well as plant organisms consist of cells
in biology the theory was introduced independently by Czech scientist
J. E. Purkyně (1837)
+
two German microscopists M. Schleiden (1838) and T. Schwann (1839)
later, German pathologist R. Virchow (1863) postulated - cells arise only
through mitotic division of pre-existing cells
c) to discover and introduce adequate methods of tissue processing for the
light microscopic examinations
- first commercially used microtomes occur during the second half of the 19th
century,
- to find new fixation and embedding methods,
- to finds of methods for visualization of cells and cellular components
( dyes originally prepared for staining of textiles were used and introduced for
stainig of cells and tissues)
History of histology and embryology in Brno
the Department of Histology and Embryology was established in 1919
three teachers and scientists achieved international reputation
Prof. MUDr. František Karel Studnička (1870 - 1955)
is founder of department and first head, he became famous
in Europe through the study of connectives tissue and
his exoplasmic theory: the all-intercellular
substances are living and arise as a result of transformation
of cell processes, he prepared and published the first czech
handbook of microscopy (Praktická mikroskopie, 1923)
Prof. MUDr. Jan Florian (1897 - 1942)
is pupil of Studnička
Florian was outstanding embryologist
in the world literature he has firstly described very young human
embryos aged only 13 to 15 days
his observations are valid to recent time
Prof. MUDr. Karel Mazanec, DrSc. (1922 - 1967)
embryologist and electron microscopist
he introduced TEM - 60 years of the last
century
he explored TEM in study of preimplantation
embryos of mammals
author of book dealing with development of
the human from the zygote to the end of the 3rd week
(published in German language - 1953)
The preparation of tissues and organs for
microscopic examination
in general, two ways are used:
- samples (specimens) prepared from living cells and tissues
- fixed samples (specimens) taken from dead organisms
Observation of living cells or tissues
is very valuable as structure and function of cells may be studied simultaneously
is mainly used in unicellular organisms and, occasionally, in free cells of a complex
organism,
preparations are not stable
- CELL AND ORGAN CULTURE - cells or fragments of tissue are removed aseptically,
transferred to a physiological medium and kept at a temperature normal for animal from which the
sample was taken. The cultures are placed in thin glass vessels or in hanging drops on a coverglas
mounted over a hollow slide
- VITAL AND SUPRAVITAL STAINING - in vital staining, dyes are injected into the living
animal. The activity of certain cells will result in the selective absorption of the coloring material by these
cells. An example of this procedure is the staining by trypan blue of macrophages on the basis of their
ability to phagocytose foreign particles. In supravital staining, a dyestuff is added to a medium of cells
already removed from the organism. Examples of this technique are the staining of mitochondria in living
cells by Janus green, of lysosomes by neutral red and of nerve fibers and cells by methylene blue.
Observation of tissues or organs from dead organism
is mostly used in histology
it has a great advantage - specimens are permanent and may be stored for
years
tissue processing for microscopic examination involves 6 phases:
sampling (taking or obtaining) of tissue probes
fixation of samples
embedding of samples
cutting of blocks and affixing of sections
staining of sections
mounting of sections
making of permanent preparations will be demonstrated this week in the
first practice
CYTOLOGY
Definition of cell: an elementary unit of living substance that is capable
basic vital functions (metabolism, autoreproduction (multiplication),
growth, movement , excitability etc.)
minimal unit
prokaryotic cells - with no nucleus and membranous organelles, DNA is
not separated from other cellular components, cells have distinct cell wall
and hyaloplasm containing plasmids and ribosomes, cell size varies from
1- 5 m (bacteria, actinomycets)
eukaryotic cells - form bodies of plants and animals, are larger and
show more complicated organization, contain prominent nucleus
surrounded by nuclear envelope, DNA is associated with histones,
eukaryotic (e.) cells utilize membranes as main material for construction
of compartments
e. cells differ in size, shape, number (in multicellular
organisms), and life-span (time)
Shape,, size
Shape
size,, and life
life--span of cells
variable
shape of cells environment (free cells
vs tissues) and function
size of cells between 10 - 30 m
ovum - 130 - 150 mm
life time of cells hours … years (nerve cells)
number of cells –
1013 -1014
Eukaryotic cell as a system
animal cell, isolated or within tissue, shows high level of organization and may be compared to
an opened system
it exchanges substances, energy and informations with its enviroment
organization of the system is maintained in the stationary status because all processes in living
cells are directed to a permanent rebuilding and establishing of the balance between them
and environment
the middle sized eukaryotic cell consists of molecular units of two kinds:
- macromolecules (of nucleic acids, proteins, lipids, and carbohydrates) - more than 4200
milliards in average
- molecules of inorganic elements (Na, K, Cl, Ca, Mg) + and molecules of water
(about 225 billions in average)
molecules associate each other to form
supramolecular complexes - ribosomes, membranes, microtubules
cell organelles - mitochondriae, Golgi apparatus, centriol, endoplasmic reticulum etc.
complex of cell organelles + nucleus + plasmalemma = a cell
main cell components observable with the light microscope have been discovered in the
second half of the 19th century
important progress in study of cell components has come with an introduction of electron
microscopy in cytology
the all eukaryotic cells consist of:
the nucleus - is the center of cellular activity that plays important role in gene expression,
heredity and cell division. The nucleus consists of several components
the cytoplasm - surrounds the nucleus and is the site of metabolic and synthetic
activities of each cell
the cell membrane - plasma membrane, plasmalemma - separates the cell from its
environment and maintains its integrity, the membrane is also engaged in creation
of the interior cellular environment
the nucleus and cytoplasm differ from each other not only in their physical and chemical
properties but also in their structural organization and function
up to date accepted structural organization of both cell compartments in the fixed cell is based
on the use of the electron microscope
Structural components of the fixed animal cell
the nucleus:
- nuclear envelope
- chromatin
- nucleolus
- nuclear cytoskeleton
(- nuclear inclusions)
the cytoplasm:
- cell organelles - are the "little organs" of the cell that posses a distinctive
structure and well established function; they are present in most cells in
different number
- mitochondria,
- endoplasmic reticulum
- ribosomes
- Golgi apparatus
- lysosomes
- peroxisosomes
- centrioles
- cell inclusions - are lifeless and have temporary character; in most cases they
are of a result of the cell activity
- stored foods (proteins, lipids and carbohydrates),
- crystals,
- pigments
- secretion granules
- hyaloplasm or cytoplasmic ground substance (cytosol) –
it is defined as a portion of the cytoplasm that surrounds the cells organelles
and inclusions
it seems to be structureless, by electron microscopy and special
immunohistochemical methods very fine network within it can be visualized –
the cytoskeleton
the cell membrane
(plasma membrane,
plasmalemma) –
separates cell from the
environment and
maintains its integrity
Structure of the unit (biological) membrane
membranes are the most frequent supramolecular structures
found in cells
apart from the plasmalemma, they separate vesicular, tubular
nd other cellular configurations
spaces limited by membranes constitute intracellular
microcompartments that serve for segregation and concentration
of substrates, products, and other substances
in cellular interior
the all membranes in cells display the same characteristic
trilaminar structure that has lead to
a concept of the unit membrane
the total thickness of the unit membrane is about 7.5 to 10 nm
unit membrane consists of
two electron-dense layers (about 2.0 thick) separated by
3.0 nm thick intermediate light layer
the intermediate or central lucent layer is formed of bimolecular layer of lipids
with hydrophilic ends of lipids proteins are associated - they form peripheral dense
layers - peripheral proteins
integral or penetrating proteins
the arrangement of lipids and proteins in the unit membrane is very dynamic and is in
permanent renewal during the cell life-time
fluid mosaic model of the membrane unit
many intracellular compartments are fabricated of unit membranes (Golgi apparatus,
endoplasmic reticulum, wall of the mitochondrion, nuclear envelope etc).
The plasma membrane and its specializations
The plasma membrane (cell membrane)
a thin limiting membrane that surrounds cell body against the
external environment
plasma membrane is not detectable by the light microscope
as viewed with the electron microscope, the plasma membrane is only 8
to 10 nm thick and shows trilaminar structure of the unit membrane
in many cells, a surface coat
composed of protein-polysaccharides
covers the outer membrane surface
= glycocalix
functions of the glycocalix:
stabilizes the cell membrane
participates in cell adhesion
is responsible for antigenic properties of the cell
is also engaged in processes of cell recognizing
Glycocalix visualized using the ruthenium red staining on
apices of nonciliated and ciliated cells in the oviduct
Specializations of cell surfaces
in cells, namely polarized epithelial ones, three distinct aspects of the plasma membrane
are distinguished:
- an apical cell surface - it borders a luminal space
- a lateral cell surface - is oriented to the adjacent cell
- a basal cell surface - it is in contact with the basal lamina
Apical cell surface
- may be smooth or is provided with microvilli, cilia
(rarely flagellum),
- in addition, it is often involved in processes of cell internalization e.g. cell drinking
or pinocytosis and phagocytosis
Microvilli
finger-like processes, 0.1 m in diameter and 0.1 to 0.5 m in length
projecting from the cell apex either irregularly or regularly and in a great number
numerous microvilli of regular dimensions are found in cells specialized to absorption and correspond with a
"brush" or "striated" border of the cell detectable by light microscopy
microvilli greatly increase the surface area of cells and facilitate the absorption of molecules or substances
microvilli
„brush border“
Cilia
are larger than microvilli and are motile, they reach 1 m in diameter and 5-10 m in length so
already well visible by the light microscope
a number of cilia that project from the free apical surface is variable (for instance about 270 cilia are on every ciliated cell in the
trachea)
cilium is covered with the plasma membrane and has core called the axoneme
the axoneme consists of
a sheaf of 9 doublet microtubules
enclosing central pair of
microtubules
each cilium terminates within the
cell at basal body (kinetosome)
with cross-striated rootlet
TEM:
SEM:
.
cilia beat with frequency 16-20 Hz/min
pseudostratified ciliated columnar epithelium
Flagellum
spermatozoon
Pinocytosis (cell drinking)
is a way of an internalization of colloid fluids surrounding the cell
the process begins by the binding of colloid molecules to the cell membrane,
after it the respective membrane parts form small pits or caveolae that then pinch off
and give to rise pinocytotic vesicles
vesicles contain internalized colloid molecules and then pass through the cytoplasm to
reach the opposite cell aspect where they fuse with the plasma membrane and release
their fluid content
exocytosis = release
of content
of pinocytotic vesicles
Phagocytosis
Lateral cell aspects
may be smooth (rarely) but may also form more or less
extensive interdigitations
intercellular space = 10 to 20 nm wide separates plasma membranes of adjacent
cells
Basal cell aspect
smooth or
in cells specialized for transport
of ions it is organized in
basolateral labyrinth
Intercellular junctions
are local specializations of lateral cell membranes between adjacent cells
in general, they serve to three functions:
increase the cellular attachment - adhering junctions
seal the intercellular space - occluding junctions
serve for cell-to-cell communication - gap or communicating
junctions
Adhering junctions:
form strong bond between adjacent cells or between basal part of the cell membrane
 spot desmosome (macula adherens)
 belt desmosome (zonula adherens)
 hemidesmosome
proteins as cadherins + desmoplakin and
plakoglobin
Spot desmosome (macula adherens) occurs especially in tissues that are
subjected to extreme mechanical stress
about 0.1 um in diameter
intercellular space is 30 nm wide and contains extracellular glycoproteins that
promote adhesion of adjacent cells
on both cytoplasmic sides of the macula adherens, there are 20 nm thick electron
dense plaques (containing special proteins - desmoplakins I and II), into
which tonofilaments insert
Spot desmosomes
Belt desmosome (zonula adherens)
encircles an epithelial cell completely
(zone
zonula)
in addition, the intercellular space is
about half as wide (15 nm)
cytoplasmic plaques are poorly develop
hemidesmosomes = junctions between the plasmalema of basal aspect and lamina
basalis
spot-like appearance
Occluding junction
= sites where plasma membranes are in
such close contact that their integral and
peripheral proteins are fused
integral proteins that are shared belong
to family occludins and claudins
are called also tight junctions or
zonulae occludentes because they
have belt-like structure and encircle
epithelial cell completely in a manner
similar to that of the belt desmosome
the function of tight junction is to seal
the extracellular space between adjacent
epithelial cells
they prevent fluid penetration
they also determine the apical and
basolateral domains in cells
Communicating junction or gap junction (nexus)
occur between a variety of excitable and non-excitable cells; serve to passage
of ions and electrical impulses in the cardiac and smooth muscle
they usually show form of plaques or spot-like regions (0.5 to 1.0 um in d.) in which
membranes of adjacent cells run in close apposition
intercellular space is retained and reduced to only 2 to 4 nm
are numerous bridges in extent of each gap
junction
are formed by a special protein, called
connexin
CELL NUCLEUS AND NUCLEOLUS – STRUCTURE
AND FUNCTION
CHROMOSOMES
the nucleus is the center of cellular activity, containing chromosomal
DNA and systems for synthesis and processing that allow the information
in the DNA to be expressed as specific proteins in the cytoplasm
with other words said
THE NUCLEUS PLAYS AN IMPORTANT ROLE IN GENE
EXPRESSION, HEREDITY, AND CELL DIVISION
- the nucleus of dividing cell
- the nucleus of interphase (not dividing) cell