Textbook for students “Fundamentals of Cytology. Cell. Basics of histology. Fabrics. For independent work of students

Concept of fabrics.
Types of fabrics.
Structure and functions
epithelial tissue.

Concept and types of fabrics

Tissue is a system of cells similar in
origin, structure and
functions and intercellular (tissue)
liquid.
The study of tissues is called
histology (Greek histos - tissue, logos
- teaching).

Types of fabrics:
-epithelial
or cover
-connective
I (fabrics
internal
environment);
- muscular
- nervous

Epithelial tissue

Epithelial tissue (epithelium) is
tissue covering the surface of the skin
eye, as well as lining all cavities
body, inner surface
hollow digestive organs,
respiratory, genitourinary systems,
found in most glands
body. There are integumentary and
glandular epithelium.

Functions of the epithelium

Pokrovnaya
Protective
excretory
Provides mobility
internal organs in serous
cavities

Classification of epithelium:

Single layer:
flat – endothelium (all vessels from the inside) and
mesothelium (all serous membranes)
cuboidal epithelium (renal tubules,
salivary gland ducts)
prismatic (stomach, intestines, uterus,
fallopian tubes, bile ducts)
cylindrical, ciliated and ciliated
(intestines, respiratory tract)
Ferrous (single or multilayer)

Classification of epithelium

Multilayer:
flat
keratinizing (epidermis
skin) and non-keratinizing (mucous
membranes, cornea of the eye) - are
cover
transition
- in the urinary tract
structures: renal pelvis, ureters,
bladder, the walls of which
subject to strong stretching

Connective tissue. Features of the structure.

Connective tissue consists of cells and
a large amount of intercellular substance,
including the main amorphous substance and
Connective tissue.
fibers.
Featuresfabric
buildings.
Connective
is a fabric
internal environment, does not come into contact with the external
environment and internal body cavities.
Participates in the construction of all internal
organs.

Functions of connective tissue:

mechanical, supporting and shaping,
makes up the body's support system: bones
skeleton, cartilage, ligaments, tendons, forming
capsule and stroma of organs;
protective, carried out by
mechanical protection (bones, cartilage, fascia),
phagocytosis and production of immune bodies;
trophic, associated with the regulation of nutrition,
metabolism and maintaining homeostasis;
plastic, expressed in active
participation in wound healing processes.

Classification of connective tissue:

Connective tissue itself:
Loose fibrous connective tissue (surrounds
blood vessels, organ stroma)
Dense fibrous connective tissue can be shaped
(ligaments, tendons, fascia, periosteum) and unformed
(mesh layer of skin)
With special properties:
adipose - white (in adults) and brown (in newborns), lipocyte cells
reticular (KKM, lymph nodes, spleen),
reticular cells and fibers
pigmented (nipples, scrotum, around the anus,
iris, moles), cells - pigmentocytes

Skeletal connective tissue:
Cartilaginous: chondroblasts, chondrocytes, collagen and
elastic fibers
hyaline (articular cartilages, costal, thyroid
cartilage, larynx, bronchi)
elastic (epiglottis, auricle, auditory
passage)
fibrous (intervertebral discs, pubic
symphysis, menisci, mandibular joint, sternoclavicular joint)
Bone:
coarse fibrous (in the embryo, in the sutures of the adult’s skull)
lamellar (all human bones)

Muscle tissue

Striated muscle tissue - all skeletal
muscles. It consists of long multi-core
cylindrical threads capable of contraction, and their ends
end with tendons. SFE – muscle fiber
Smooth muscle tissue - found in the walls of hollow
organs, blood and lymphatic vessels, in the skin and
choroid of the eyeball. Cut smooth
muscle tissue is not subject to our will.
Cardiac striated muscle tissue
cardiomyocytes are small in size, have one or two nuclei,
abundance of mitochondria, do not end with tendons, have
special contacts - nexuses for transmitting impulses. Not
regenerate

Nervous tissue

The main functional property
nervous tissue is excitability and
conductivity (transmission of impulses). She
able to perceive irritations from
external and internal environment and transmit
them along their fibers to other tissues and
organs of the body. Nervous tissue consists of
neurons and supporting cells –
neuroglia.

Neurons are
polygonal cells with
processes along which they are carried out
impulses. Neurons extend from the cell body
two types of shoots. The longest of
them (the only one), conducting
irritation from the neuron body - axon.
Short branching shoots
by which impulses are conducted along
direction towards the neuron body are called
dendrites (Greek dendron - tree).

Types of neurons by number of processes

unipolar – with one axon, rarely
meet
pseudounipolar - the axon and dendrite of which
begin from the general growth of the cell body with
subsequent T-shaped division
bipolar - with two processes (axon and
dendrite).
multipolar – more than 2 processes

Types of neurons by function:

afferent (sensitive) neurons
- carry impulses from receptors to reflex
center.
intercalary neurons
- carry out communication between neurons.
efferent (motor) neurons transmit impulses from the central nervous system to effectors
(executive bodies).

Neuroglia

Neuroglia from everyone
sides surrounds
neurons and makes up
stroma of the central nervous system. Cells
neuroglia 10 times
more than
neurons, they can
share. Neuroglia
is about 80%
brain mass. She
performs in nervous
support tissue,
secretory,
trophic and
protective functions.

Nerve fibers

these are processes (axons) of nerve cells, usually covered
shell. A nerve is a collection of nerve fibers
enclosed in a common connective tissue membrane.
The main functional property of nerve fibers
is conductivity. Depending on the structure
Nerve fibers are divided into myelin (pulp) and
nonmyelinated (pulpless). At regular intervals
the myelin sheath is interrupted by nodes of Ranvier.
This affects the speed of excitation along
nerve fiber. Excitation in myelin fibers
transmitted spasmodically from one interception to another with
high speed, reaching 120 m/s. IN
non-myelinated fibers, rate of excitation transmission
does not exceed 10 m/s.

Synapse

From (Greek synaps - connection, connection) - connection between
presynaptic axon terminal and membrane
postsynaptic cell. In any synapse there are three
main parts: presynaptic membrane, synaptic
cleft and postsynaptic membrane. Connective tissue is the most diverse, including a whole group of tissues that are not similar to each other. There are 2 criteria by which different tissues are combined into one group: a) the presence of an intercellular substance, which is produced by the cells themselves and which only connective tissue has. The intercellular substance consists of the ground substance and collagen, elastic, reticular fibers. Main substance is a colloid that has the appearance of a gel. There are 2 components in it. The first is called amorphous and consists of glycosaminoglycans and proteoglycans (they include polysaccharides and proteins). Its concentration determines the consistency of a given tissue. For example, there is a lot of amorphous substance in cartilage, which determines its density. The second component of the intercellular substance of the fiber. Collagen fibers long, convoluted, relatively thick (up to 10 microns in diameter - 50 times thinner than a hair). They contain the protein collagen, which is capable of swelling (swelling in kidney disease, inflammation), gives the tissue strength and allows it to stretch. Elastic fibers much straighter and thinner (1 µm), forming a wide-loop network. Their function is to return the fabric to its original position after it has been stretched. Reticular fibers(from Latin reticulum - mesh) are close in composition to immature collagen fibers. These are thin threads that go in different directions and form a delicate mesh. b) it connects other tissues with each other, fills voids, forms “linings”, “wrappers”, that is, it connects the body into one whole. Connective tissue performs a supporting (mechanical) function (formation of the framework of organs, their shells - fascia, as well as ligaments, tendons), protective (production of immune bodies), trophic (cell nutrition, metabolism), plastic (participation in wound healing, scar formation ) There are connective tissue itself, cartilage and bone. 1. The connective tissue itself is represented by loose and dense fibrous connective tissue. Loose fibrous (unformed) connective tissue(Fig. 2/6.) – “the most connecting”. It consists of the main substance, which contains elastic and collagen fibers, differently oriented in the main substance depending on the structure and function of the organ, and various cellular elements: fibroblasts (from Latin fibra - fiber and Greek blastos - sprout, germ , have a developed endoplasmic reticulum in which the proteins collagen and elastin are created, building the corresponding fibers of the intercellular substance), macrophages (cells capable of phagocytosis), mast cells (contain biologically active substances: heparin, which prevents blood clotting, and histamine, which is involved in inflammatory and allergic reactions), plasma cells (participate in the synthesis of antibodies), poorly differentiated cells (capable of turning into other cells of connective tissue), fat, pigment cells, etc. This tissue is located mainly along the blood vessels, surrounds them (in the aorta in the form of a pillow – adventitia), and forms the stroma of various organs, thus performing a supporting function, plays a protective role due to the presence of the special cells described above, a plastic one, and also participates in metabolic processes in the body. Dense fibrous connective tissue characterized by a large number of fibers and a small number of cells and the amorphous component of the intercellular substance. It can be formalized or unformed. IN dense, unformed connective tissue(Fig. 2/7.) Numerous connective tissue fibers are densely intertwined, and between them there is a small number of cellular elements oriented in different directions (for example, the mesh layer of the skin, which gives it a certain strength). Densely formed connective tissue(Fig. 2/8.) often called white fibrous, it is distinguished by an ordered arrangement of bundles of fibers running in a certain direction parallel to each other. This device gives strength to the structures into which it is included and allows them to withstand heavy loads. It consists of tendons, ligaments, fascia that separates individual muscles from each other, the dura mater, the periosteum that covers the bones, the tunica albuginea of the eyeball and some other anatomical formations. 2. Reticular tissue (Fig. 2/9.) forms the skeleton of hematopoietic organs and organs immune systems s (bone marrow, thymus, spleen, lymph nodes, group and single lymphoid nodules) and is part of some internal organs (kidneys, etc.). Consists of reticular cells and reticular fibers. Reticular cells – reticulocytes have numerous processes that connect with each other, forming a mesh frame. They, like fibroblasts, synthesize reticular fibers. A characteristic property of reticulocytes is that some of them have the ability to phagocytose, while others are able to transform into other cellular forms (for example, macrophages, hematopoietic ones), that is, they belong to the category of stromal elements. In the loops formed by the reticular tissue, blood-forming and immunocompetent cells are located. This type of tissue provides hematopoiesis. Almost all blood cells spend their childhood in reticular tissue. With age and with pathological changes, the functions of hematopoietic and lymphoid organs are disrupted. Now scientists are working on a very important problem - reticulocyte cloning. 3. Adipose tissue (Fig. 2/10.) is formed under the skin of almost all areas of the body, with the exception of the eyelids, penis and skull, and is especially developed under the peritoneum, in the omentum. It does not have its own basic substance and is formed during the accumulation of lipid (fatty) inclusions in the cytoplasm of fibroblasts - young cells of loose fibrous connective tissue, the layers of which are divided into lobules of various sizes. Fat cells – lipocytes press closely against each other, allowing only capillaries (and therefore fibroblasts with fibers) to pass between them. In each cell, a fat drop is located in the center, the cytoplasm is practically lost, and the nucleus is displaced to the periphery. Functions of adipose tissue: - the most important source of energy and water depot. When it is broken down, much more energy is released than when using proteins and carbohydrates. In addition, a large amount of water is formed; - forms a protective cover of the body; - keeps organs in a normal anatomical position (for example, the kidneys in the retroperitoneal space are surrounded by a pronounced fat capsule); - a special type of adipose tissue is found in the skin of newborns - brown adipose tissue, which retains a large number of mitochondria, and therefore it is an important source of heat for babies. 4. Pigment tissue (Fig. 2/ 11.) is found almost everywhere where there is intense coloring: hair, tanned skin, moles, nipple area, retina of the eyeball. This tissue is made up of cells - melanocytes, which are filled with animal pigment - melanin. They are star-shaped; the cytoplasm diverges into petals from the nucleus located in the center. These cells may cause malignant tumor– melanoma, affecting the skin, eyes, and digestive organs. This disease progresses rapidly and metastasizes very early. 5. Cartilage tissue consists of cartilage cells ( chondrocytes), located one at a time or in groups, and the main substance in a gel state. This clear, bluish-white substance is dense and less hard than bone. Cartilage does not have blood vessels and is fed from the blood vessels of the perichondrium, which covers the outside of the cartilage and consists of dense fibrous tissue in which there are young cells - chondroblasts(cells that form cartilage). As they “grow up,” chondroblasts move into the amorphous substance of cartilage, where they are called chondrocytes. When a chondrocyte divides, the daughter cells, due to the density of the intercellular substance, are unable to separate, so they remain together. Cartilage is elastic, plays a predominantly mechanical role, and is found primarily in joints and developing bones. The embryo initially has cartilage instead of bones, which is gradually replaced by bone tissue, and after birth only the growth zones remain cartilaginous. In adults, when growth is complete, cartilage covers only the articular surfaces of the bones. Depending on the characteristics of the intercellular substance, hyaline, fibrous and elastic cartilages are distinguished (Fig. 2/12.). Hyaline cartilage contains predominantly ground substance and a small amount of collagen fibers. Hard and elastic in the body, it is most common: at the junction of the ribs with the sternum, in the respiratory tract, on the articular surfaces of bones, and makes up most of the skeleton of the intrauterine fetus. In the elderly, hyaline cartilage can calcify. Fibrous cartilage in the intercellular substance it contains a large number of collagen fibers, between which cartilage cells are located. This is a strong tissue and is found in places that are subject to significant mechanical stress: in the intervertebral and articular discs, menisci, pubic symphysis, in areas of tendons and ligaments at their attachment points, in the temporomandibular and sternoclavicular joints. Elastic cartilage contains many elastic fibers and does not undergo calcification. It forms the auricle, epiglottis, laryngeal cartilage, cartilaginous part of the auditory tube and external auditory canal. When compressed or bent, these structures easily change their shape and also quickly return to their original position, that is, they are elastic. 6. Bone tissue is distinguished by special mechanical properties due to its characteristic feature - calcification of the intercellular substance. All the bones of the skeleton are made of bone tissue, which perform a supporting and protective role and participate in movements. Besides, bone tissue is a depot of minerals. It consists of bone cells embedded in calcified intercellular substance containing collagen (ossein) fibers, which are strictly oriented in the compact substance of the bone and random in the spongy substance, and inorganic salts (mainly calcium and phosphorus salts). The amorphous component is practically absent. There are 3 types of cells found in bone tissue: osteoblasts(1)– young cells containing a large number of organelles. They are located in the most superficial layer of bones - the periosteum. From them the intercellular substance of bone and mature bone cells are formed - osteocytes(2)– multi-processed cells with a reduced number of organelles and a large supply of glycogen. Osteoclasts(3)– bone-destroying cells. It is thanks to osteoclasts that the fetus undergoes destruction of cartilage, followed by replacement with bone tissue, as well as resorption (resorption) of aging bone, followed by its replacement with a new one. Depending on the location of the ossein fiber bundles, two types of bone tissue are distinguished: coarse-fiber and lamellar. Rough fibrous bone tissue differs in that both the bundles of fibers and the fibers themselves are located in different directions. Such tissue is present in the fetus and child, but in adults it is preserved only in the area of the sutures of the skull and in the places where the tendons attach to the bones. Lamellar bone tissue forms the compact and spongy substance of adult bones. This is a durable tissue consisting of bone plates, in which the fibers are arranged in the form of parallel oriented bundles, and the direction of the bundles in different bone plates is not the same.

Tissues are a collection of cells and non-cellular structures (non-cellular substances) that are similar in origin, structure and functions. There are four main groups of tissues: epithelial, muscle, connective and nervous.

... Epithelial tissue covers the outside of the body and lines the inside of hollow organs and the walls of body cavities. A special type of epithelial tissue - glandular epithelium - forms the majority of glands (thyroid, sweat, liver, etc.).

... Epithelial tissues have the following features: - their cells are closely adjacent to each other, forming a layer, - there is very little intercellular substance; — cells have the ability to recover (regenerate).

... Epithelial cells can be flat, cylindrical, or cubic in shape. Based on the number of layers, epithelium can be single-layered or multilayered.

... Examples of epithelium: single-layer squamous lining the thoracic and abdominal cavities of the body; multi-layered flat forms the outer layer of skin (epidermis); single-layered cylindrical lines most of the intestinal tract; multilayer cylindrical - cavity of the upper respiratory tract); single-layer cubic forms the tubules of the nephrons of the kidneys. Functions of epithelial tissues; borderline, protective, secretory, absorption.

CONNECTIVE TISSUE PROPER CONNECTIVE SKELETAL Fibrous Cartilaginous 1. loose 1. hyaline cartilage 2. dense 2. elastic cartilage 3. formed 3. fibrous cartilage 4. unformed With special properties Bone 1. reticular 1. coarse fibrous 2. adipose 2. : 3. mucosa compact substance 4. pigment spongy substance

... Connective tissues (tissues of the internal environment) unite groups of tissues of mesodermal origin, very different in structure and functions. Types of connective tissue: bone, cartilage, subcutaneous fatty tissue, ligaments, tendons, blood, lymph, etc.

... Connective tissues A common characteristic feature of the structure of these tissues is the loose arrangement of cells separated from each other by a well-defined intercellular substance, which is formed by various fibers of a protein nature (collagen, elastic) and the main amorphous substance.

... Blood is a type of connective tissue in which the intercellular substance is liquid (plasma), due to which one of the main functions of blood is transport (transports gases, nutrients, hormones, end products of cell activity, etc.).

... The intercellular substance of loose fibrous connective tissue, located in the layers between organs, as well as connecting the skin with muscles, consists of an amorphous substance and elastic fibers freely located in different directions. Thanks to this structure of the intercellular substance, the skin is mobile. This tissue performs supporting, protective and nutritional functions.

... Muscle tissue determines all types of motor processes within the body, as well as the movement of the body and its parts in space.

... This is ensured due to the special properties of muscle cells - excitability and contractility. All muscle tissue cells contain the finest contractile fibers - myofibrils, formed by linear protein molecules - actin and myosin. When they slide relative to each other, the length of the muscle cells changes.

... Striated (skeletal) muscle tissue is built from many multinucleated fiber-like cells 1-12 cm long. All skeletal muscles, muscles of the tongue, muscles of the walls of the oral cavity, pharynx, larynx, upper part of the esophagus, facial muscles, and diaphragm are built from it. Figure 1. Fibers of striated muscle tissue: a) appearance fibers; b) cross section of fibers

... Features of striated muscle tissue: speed and arbitrariness (i.e., dependence of contraction on the will, desire of a person), consumption of large amounts of energy and oxygen, rapid fatigue. Figure 1. Fibers of striated muscle tissue: a) appearance of the fibers; b) cross section of fibers

... Cardiac tissue consists of cross-striated mononuclear muscle cells, but has different properties. The cells are not arranged in a parallel bundle, like skeletal cells, but branch, forming a single network. Thanks to many cellular contacts, the incoming nerve impulse is transmitted from one cell to another, ensuring simultaneous contraction and then relaxation of the heart muscle, which allows it to perform its pumping function.

... Smooth muscle tissue cells do not have transverse striations, they are spindle-shaped, mononuclear, and their length is about 0.1 mm. This type of tissue is involved in the formation of the walls of tube-shaped internal organs and vessels (digestive tract, uterus, bladder, blood and lymphatic vessels).

... Features of smooth muscle tissue: - involuntary and low contraction force, - ability for long-term tonic contraction, - less fatigue, - low need for energy and oxygen.

... The nervous tissue from which the brain and spinal cord, nerve ganglia and plexuses, peripheral nerves are built, performs the functions of perception, processing, storage and transmission of information coming from both environment, and from the organs of the body itself. The activity of the nervous system ensures the body's reactions to various stimuli, regulation and coordination of the work of all its organs.

... Neuron - consists of a body and processes of two types. The neuron body is represented by the nucleus and the surrounding cytoplasm. This is the metabolic center of the nerve cell; when it is destroyed, she dies. Neuron bodies are located predominantly in the brain and spinal cord, i.e. in the central nervous system(CNS), where their clusters form the gray matter of the brain. Clusters of nerve cell bodies outside the central nervous system form nerve ganglia, or ganglia.

Figure 2. Different shapes of neurons. a - nerve cell with one process; b - nerve cell with two processes; c - a nerve cell with a large number of processes. 1 - cell body; 2, 3 - processes. Figure 3. Scheme of the structure of a neuron and nerve fiber 1 - neuron body; 2 - dendrites; 3 - axon; 4 - axon collaterals; 5 - myelin sheath of the nerve fiber; 6 - terminal branches of the nerve fiber. The arrows show the direction of propagation of nerve impulses (according to Polyakov).

... The main properties of nerve cells are excitability and conductivity. Excitability is the ability of nervous tissue to enter a state of excitement in response to stimulation.

... conductivity is the ability to transmit excitation in the form of a nerve impulse to another cell (nervous, muscle, glandular). Thanks to these properties of nervous tissue, the perception, conduct and formation of the body's response to the action of external and internal stimuli is carried out.

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Introduction

histology tissue genetic

The study of the basics of histology is an important link in understanding the structure of the human body, since tissues represent one of the levels of organization of living matter, the basis for the formation of organs. History of the development of histology in late XIX V. in Russia was closely connected with the formation of university education.

The purpose of the work is to define histology as a science.

The stated goal determines the research objectives:

1. Study the objects and methods of histology research;

2. Identify the historical stages in the development of histology.

1. DefinitionhistologyHowscience

Histology - (from the Greek histos - tissue, logos - study) - the science of the structure, development and vital functions of human and animal tissues.

From this definition it follows that the main subject of the study of histology is tissue. There are 5 main tissues in the human and animal body:

· Nervous;

· Muscular;

· Epithelial;

· Connecting;

each of which has its own characteristics.

Tissues are a system of cells and non-cellular structures, united and specialized in the process of phylogenesis and ontogenesis to perform essential functions in the body.

Thus, the basis for the development and structure of tissues are cells and their derivatives - non-cellular structures.

Histology, how academic discipline, includes the following sections:

· cytology;

· embryology;

general histology; (studies the structure and functions of tissues);

· private histology (studies the structure and functions of tissues).

The subject of general histology (the actual study of tissues) is both general patterns and distinctive features the structure of specific tissues, the subject of particular histology - the patterns of vital activity and interaction of tissues in specific organs.

Current tasks of histology are:

· development of a general theory of histology, reflecting the evolutionary dynamics of tissues and patterns of embryonic and postnatal histogenesis;

· study of histogenesis as a complex of processes of proliferation, differentiation, determination, integration, adaptive variability, programmed cell death, etc., coordinated in time and space;

· elucidation of the mechanisms of homeostasis and tissue regulation (nervous, endocrine, immune), as well as age-related tissue dynamics;

· study of patterns of reactivity and adaptive variability of cells and tissues under the influence of unfavorable environmental factors and under extreme conditions of functioning and development, as well as during transplantation;

· development of the problem of tissue regeneration after damaging effects and methods of tissue replacement therapy;

· disclosure of the mechanisms of molecular genetic regulation of cell differentiation, inheritance of a genetic defect in the development of human systems, development of methods of gene therapy and embryonic stem cell transplantation;

· elucidation of the processes of human embryonic development, critical periods of development, reproduction and causes of infertility.

But the main task of histology, like other biological sciences, is to identify the essence of life, structural organization vital processes for targeted influence on them, which is very important for medical practice. Based on the main task, histology studies the patterns of formation, mechanisms of regulation of tissue morphogenesis processes and the role of the nervous, endocrine and immune systems in these processes. The most important tasks solved by histology are the study of cellular and tissue compatibility during blood transfusion, tissue and organ transplantation. Histology is closely related to other biomedical sciences - biology, anatomy, physiology, biochemistry, pathological anatomy and clinical disciplines. In addition, modern histology largely uses the achievements of physics, chemistry, mathematics, cybernetics, which determines its close connection with these sciences.

2. Objectsresearchhistology

Objects of research are divided into:

· living (cells in a drop of blood, cells in culture, etc.);

· dead or fixed, which can be taken from either a living organism (biopsy) or from cadavers.

To study living microobjects, methods are used to implant transparent chambers with the cells being studied into the animal’s body, transplanting cells into the fluid of the anterior chamber of the eye and monitoring their vital functions through the transparent cornea of the eye. The most common methods of intravital study of structures are cell and tissue cultures - suspension (suspension in a liquid medium) and monolayer (formation of a continuous layer on glass). For long-term maintenance of cells in culture, it is necessary to create an optimal temperature corresponding to body temperature and a special nutrient medium (blood plasma, embryonic extract, growth stimulants) to maintain basic vital signs: growth, reproduction, movement, differentiation.

To study dead, or fixed, cells and tissues, they usually must be subjected to special processing to obtain a histological specimen for examination under a light or electron microscope.

The histological specimen can be in the form of:

· thin stained section of an organ or tissue;

· smear on glass (for example, blood smear, bone marrow);

· an imprint on glass from a broken organ (for example, the mucous membrane of the oral cavity, vagina, etc.);

· thin film preparation (for example, peritoneum, pleura, meninges).

3. Preparationhistologicaldrugs

A histological specimen of any form must meet the following requirements:

· maintain the lifetime state of structures;

· be thin and transparent enough to be examined under a microscope in transmitted light;

· be contrasting, that is, the structures being studied must be clearly visible under a microscope;

· preparations for light microscopy must be preserved for a long time and used for repeated study.

These requirements are achieved during the preparation of the drug.

The following stages are distinguished in the preparation of a histological specimen.

Taking material (a piece of tissue or organ) to prepare a drug. The following points are taken into account:

· material collection should be carried out as soon as possible after the death or slaughter of the animal, and, if possible, from a living object (biopsy), so that the structures of the cell, tissue or organ are better preserved;

· the pieces should be collected with a sharp instrument so as not to injure the tissue;

· the thickness of the piece should not exceed 5 mm so that the fixing solution can penetrate into the thickness of the piece;

· the piece must be marked (indicate the name of the organ, the number of the animal or the name of the person, the date of collection, and so on).

Fixation of the material is necessary to stop metabolic processes and preserve structures from decay. Fixation is most often achieved by immersing the piece in fixing liquids, which can be simple alcohols and formalin and complex Carnoy's solution, Zinker's fixative and others. The fixative causes denaturation of the protein and thereby stops metabolic processes and preserves the structures in their lifetime state. Fixation can also be achieved by freezing (cooling in a CO 2 stream, liquid nitrogen, etc.). The duration of fixation is selected empirically for each tissue or organ.

Pouring pieces into sealing media (paraffin, celloidin, resins) or freezing for subsequent production of thin sections.

Preparation of sections on special devices (microtome or ultramicrotome) using special knives. Sections for light microscopy are glued onto glass slides, and for electron microscopy they are mounted on special grids.

Staining or contrasting sections (for electron microscopy). Before staining the sections, the sealing medium is removed (dewaxing). The contrast of the studied structures is achieved by coloring. Dyes are divided into basic, acidic and neutral. The most widely used dyes are basic (usually hematoxylin) and acidic (eosin). Complex dyes are often used.

Clearing of sections (in xylene, toluene), encapsulation in resin (balsam, polystyrene), covering with a coverslip. After these sequential procedures, the drug can be studied under a light microscope.

For the purposes of electron microscopy, there are some peculiarities in the preparation stages of preparations, but the general principles are the same. The main difference is that the histological preparation for light microscopy can be stored for a long time and reused. Sections for electron microscopy are used once. In this case, first, the objects of interest in the drug are photographed, and the structures are studied using electron diffraction patterns.

From tissues of liquid consistency (blood, bone marrow and others), preparations are made in the form of a smear on a glass slide, which are also fixed, stained, and then studied.

From fragile parenchymal organs (liver, kidney and others), preparations are made in the form of an imprint of the organ: after a fracture or rupture of the organ, a glass slide is applied to the site of the organ fracture, onto which some free cells are glued. The preparation is then fixed, stained and examined.

Finally, film preparations are made from some organs (mesentery, pia mater) or from loose fibrous connective tissue by stretching or crushing between two glasses, also followed by fixation, staining and pouring into resins.

4. Methodsresearch

The main method for studying biological objects used in histology is microscopy, i.e., studying histological preparations under a microscope. Microscopy can be an independent method of study, but recently it is usually combined with other methods (histochemistry, historadiography and others). It should be remembered that different microscope designs are used for microscopy, allowing one to study different parameters of the objects being studied. The following types of microscopy are distinguished:

· light microscopy (resolution 0.2 microns) is the most common type of microscopy;

· ultraviolet microscopy (resolution 0.1 microns);

· luminescent (fluorescent) microscopy to determine chemical substances in the structures under consideration;

· phase-contrast microscopy for studying structures in unstained histological preparations;

· polarization microscopy for studying mainly fibrous structures;

· dark field microscopy for studying living objects;

· incident light microscopy for studying thick objects;

· electron microscopy (resolution up to 0.1-0.7 nm), its two varieties transmission (transmission) electron microscopy and scanning or raster microscopy provide an image of the surface of ultrastructures.

Histochemical and cytochemical methods make it possible to determine the composition of chemical substances and even their quantity in the structures being studied. The method is based on carrying out chemical reactions with the reagent used and chemicals present in the substrate, with the formation of a reaction product (contrast or fluorescent), which is then determined by light or fluorescent microscopy.

The method of histoautoradiography makes it possible to identify the composition of chemical substances in structures and the intensity of exchange based on the inclusion of radioactive isotopes in the structures under study. The method is most often used in animal experiments.

The differential centrifugation method makes it possible to study individual organelles or even fragments isolated from a cell. To do this, a piece of the organ under study is ground, filled with saline, and then accelerated in a centrifuge at various speeds (from 2 to 150 thousand) and the fractions of interest are obtained, which are then studied by various methods.

The interferometry method allows you to determine the dry mass of substances in living or fixed objects.

Immunomorphological methods allow, using pre-conducted immune reactions, based on antigen-antibody interaction, to determine subpopulations of lymphocytes, determine the degree of foreignness of cells, carry out histological typing of tissues and organs (determine histocompatibility) for organ transplantation.

Cell culture method (in vitro, in vivo) - growing cells in a test tube or in special capsules in the body and subsequent study of living cells under a microscope.

Units of measurement used in histology

To measure structures in light microscopy, micrometers are mainly used: 1 µm is 0.001 mm; Electron microscopy uses nanometers: 1 nm is 0.001 microns.

5. Historicalstagesdevelopmentscience

In the history of the development of histology, three periods are conventionally distinguished:

· The pre-microscopic period (from the 4th century BC to 1665) is associated with the names of Aristotle, Galen, Avicenna, Vesalius, Fallopius and is characterized by attempts to isolate heterogeneous tissues (hard, soft, liquid, etc.) in the body of animals and humans ) and the use of anatomical preparation methods;

· Microscopic period (from 1665 to 1950). The beginning of the period is associated with the name of the English physicist Robert Hooke, who, firstly, improved the microscope (it is believed that the first microscopes were invented in the very early XVII c.), secondly, he used it for the systematic study of various, including biological, objects and published the results of these observations in 1665 in the book “Micrography”, thirdly, he first introduced the term “cell” (“cellulum”) . Subsequently, microscopes were continuously improved and used increasingly for the study of biological tissues and organs. Special attention focused on the study of cell structure. Jan Purkinje described the presence of “protoplasm” (cytoplasm) and a nucleus in animal cells, and a little later R. Brown confirmed the presence of a nucleus in most animal cells. The botanist M. Schleiden became interested in the origin of cells by cytogenesis. The results of these studies allowed T. Schwan, based on their reports, to formulate the cell theory (1838-1839) in the form of three postulates:
- all plant and animal organisms consist of cells;
- all cells develop according to general principle from cytoblastema;
- each cell has independent vital activity, and the vital activity of the body is the sum of the activities of the cells.

However, soon R. Virchow (1858) clarified that cell development is carried out by dividing the original cell (any cell from a cell). The provisions of the cell theory developed by T. Schwan are still relevant today, although they are formulated differently.

Modern provisions of cell theory:

· a cell is the smallest unit of a living thing;

· cells of animal organisms are similar in structure;

· cell reproduction occurs by dividing the original cell;

· multicellular organisms are complex ensembles of cells and their derivatives, united in systems of tissues and organs, interconnected by cellular, humoral and neural forms of regulation.

Further improvement of microscopes, especially the creation of achromatic lenses, made it possible to identify smaller structures in cells:

Cell center Hertwig, 1875;

Reticular apparatus or lamellar complex of Golgi, 1898;

Mitochondria Bend, 1898

· The modern stage of development of histology begins in 1950 with the beginning of the use of the electron microscope to study biological objects, although the electron microscope was invented earlier (E. Ruska, M. Knoll, 1931). However, the modern stage of development of histology is characterized by the introduction of not only the electron microscope, but also other methods:

· cyto- and histochemistry;

· historadiography;

· other modern methods listed above.

In this case, a complex of various techniques is usually used, which allows one to form not only a qualitative idea of the structures being studied, but also to obtain accurate quantitative characteristics. Various morphometric techniques are currently used especially widely, including automated systems processing the received information using computers.

Conclusions

1. The main objects are living or dead tissues. Research methods include a microscope, histochemical and cytochemical methods, histoautoradiography, differential centrifugation, interferometry, immunomorphological methods and cell cultivation.

2. In the history of the development of histology, there are three stages: the pre-croscopic period, the microscopic period and the modern period.

Listliterature

1. Radostina A.I., Yurina N.I. Histology: Textbook. - M.: Medicine, 1995. - 256 p.

2. Ham A., Cormack D. Histology, vol. 1-5. - M., 1982-1983.

3. Posted on Allbest.ru

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STORY. COMPARATIVE FRAMEWORK GANDSTOLOGIES

Histology is the study of the development, structure, vital activity and regeneration of tissues of animal organisms and the human body.

There are several levels of structural organization of the body:

1. molecular;

2. subcellular:

3. cellular;

4. fabric;

5. organ;

6. systemic;

7. organismic.

The branches of histology are: cytology, embryology (the study of the embryo), general histology (the science of tissues), special histology (the science of the histophysiology of organs).

Histology as a science has its own research methods:

1. Comparative or descriptive;

2. Experimental.

These methods are based on the use of various optical techniques, so three stages in the development of histology can be distinguished:

1. Pre-microscopic. lasted more than 2000 years (beginning 400 BC).

2. Microscopic, lasted about 300 years. The beginning is associated with the construction of the first microscopes and the improvement of modern ones. The first microscope was created in 1610 (G. Galileo). In 1665 English physicist R. Hooke, examining a section of cork under a microscope, discovered that it consisted of cells resembling a honeycomb. Hooke called these formations cells (Latin se11a - cell, cell). Hooke noted the same structure in the core of elderberry, reed and some other plants. In the second half of the 17th century. The works of a number of microscopists appeared: the Italian M. Malpighi. Englishman N. Grew, who also discovered the cellular structure of many plant objects. The Dutchman A. Leeuwenhoek was the first to discover single-celled organisms in water. The Czech scientist J. Purkinė called the semi-liquid gelatinous contents of the cell protoplasm. The English botanist B. Brown discovered the nucleus. The German zoologist T. Schwann in 1839 summarized all the data that had been obtained before him and put forward the main provisions of the cell theory. R. Virchow also made a major contribution by developing and expanding the cell theory; He wrote the work "Cellular Pathology".

Only in the mid-19th century did histology emerge from microscopic science. During the same period, histology began to develop intensively in Russia. At first, histology was taught to students at the Department of Anatomy and Physiology. Therefore, the first histologists were anatomists, physiologists and embryologists. The first department of histology was opened at Moscow University in 1864 by Professor Ovsyannikov. At the same time, a department was opened at the Military Medical Academy, headed by Lavdovsky. Only 13 years later the first textbook by Ovsyannikov and Lavdovsky appeared in Russia. The Moscow Department of Histology was headed by A.I. Babukhin. Representatives of these three schools in their studies pursued a clear histophysiological position, i.e. not only described the structure, but tried to explain the regularity of the structure, therefore the physiological orientation is a priority for domestic histology.

The Kazan school of morphologists is known for its works in the field of studying nervous tissue, including leading researcher. Arnstein. Smirnov and Dogel became the founders of this direction. Therefore, in Russia, many questions about the structure of organs and tissues began to be considered from the perspective of nervous regulation. This was also facilitated by Botkin’s work. Pavlova and Sechenov.

At the beginning of the 20th century, evolutionary approaches began to develop most intensively in histology, based on the work of Darwin and Haeckel. Thanks to the work of embryologists Wolf, Nanlsr, Mechnikov and Kovalevsky, research in the field of embryology was continued and evolutionary approaches were supported.

The focus of the Soviet histological school was clear in relation to the clinic, so most of the histological work was aimed at solving clinical problems.

3. The current stage of development of histology is associated with a more subtle study of structures. Thanks to the use of optical, light-optical. Electron microscopy, histochemical, quantitative methods, cytophotometry, organs were studied for cellular level, subcellular structures, molecular structures. Tasks of histology.

1. study of structures at the systemic, organ, cellular and molecular levels;

2. study of the physiology of structures at all levels;

3. study of the patterns of differentiation and regeneration:

4. study of age-related characteristics of tissues and cellular structures, including patterns of embryogenesis:

5. study of patterns of adaptation of structures at all levels, primarily related to environmental problems;

6. study of the patterns of nervous, endocrine, immune regulation.

BASICS OF COMPARATIVE EMBRYOLOGY

Embryology is the science of the development and structure of the human embryo.

The objectives of medical embryology are the study of: progenesis, stages of embryogenesis (from fertilization to the moment of birth), mechanisms of embryogenesis. Disorders of embryonic development, the occurrence of causes of developmental disorders, the study of critical periods, the development of preventive measures and the study of postnatal development (i.e. development after birth) until the period of complete formation of all organs and systems of the body. Development is divided into: the historical development of an organism (phylogeny) and the non-individual development of an organism (ontogenesis). In ontogenesis, embryogenesis and postnatal development are distinguished. The earliest method of studying embryology is the descriptive method, then comparative and experimental (this is, first of all, artificial insemination) methods.

The following periods are distinguished in embryogenesis:

Fertilization:

Cleavage: histology embryology science

Gastrulation:

Histogenesis;

Organogenesis:

Systemogenesis:

Formation of the body as a whole.

Fertilization is one of the stages of embryogenesis. This process involves many male germ cells and one female. But only the nucleus of one sperm, merging with the egg, forms a one-celled embryo - a zygote, which carries maternal and paternal hereditary genetic factors. Fertilization at the beginning of evolution was an external process. As animals reached land, eggs began to be released into the external air. In this regard, various protective shells appeared: shell. protein, yolk. Male germ cells cannot pass through these membranes, therefore such an egg can be fertilized only before the membranes are formed, i.e. inside the body. This is how internal fertilization occurs.

Male reproductive cells - spermatozoa - differ little from various types animals and humans. They are produced in large quantities and are small and highly mobile cells.

Female reproductive cells - eggs - have undergone a more complex evolution. They are large, sedentary cells.

Produced in small quantities. They differ from each other in the quantity and distribution of nutritious yolk material, as well as in size.

There are several types of eggs. The type of egg depends on the duration of the embryonic development of the organism, on the complexity of its structure, on the conditions of development and on whether or not there is a larval stage. First, the primary isoleital eggs appeared. They contain little yolk, and it is evenly distributed throughout the entire volume of the cell, with a diameter of about 100 microns. Animals with this type of egg develop in an aquatic environment. Telolecithal eggs then appear. Their yolk content increases, and it is predominantly localized at the vegetative pole. The size of the eggs also increases. Among them are moderately telolecithal (amphibians, reptiles) and strongly telolecithal (birds) with a very high yolk content. which is entirely focused on the vegetative pole. Then a second isolecithal egg appears (in higher mammals and humans). Its size is about 100 microns. Contains a small amount of yolk, which is evenly distributed throughout the cytoplasm. Around the cell there is a shiny membrane, which is surrounded on the outside epithelial cells- "radiant crown". The development of such organisms occurs in utero in the mother’s body.

The reasons for the appearance of a secondary isolecithal egg are:

a) complication of the body of an adult;

b) increasing the timing of embryonic development;

c) change in the development environment (mother’s organism);

d) disappearance of intermediate larval stages.

After fertilization, the process of fragmentation begins, as a result of which a multicellular embryo is obtained, which in humans has the appearance of a cellular nodule - a morula. Then a cavity appears in the primary nodule and a germinal vesicle or blastula is formed. During the process of fragmentation, the embryo does not increase in size, but only the number of cells (blastomeres) that compose it increases.

The type of cleavage is determined by the type of egg. There are:

In animals with primarily isolecithal eggs (lancelet), the cleavage is complete and uniform. With this type of fragmentation, blastomeres do not differ qualitatively from each other, because intracellular differentiation does not occur;

In animals with a moderately telolecithal egg (amphibians), the cleavage is complete, but uneven;

In animals with a sharply telolecithal egg (birds), the cleavage is incomplete, discoidal:

In mammals (and humans) that have a secondary isolecithal egg, cleavage is complete, uneven and asynchronous. In this case, an odd number of blastomeres are formed. Moreover, some of them go to the formation of the embryo, while others go to the formation of provisional organs (for example, trophoblast), which create conditions for the development of the embryo.

After the formation of the blastula, the process of gastrulation begins. At the early stage, a two-layer embryo is formed, and at a later stage, a three-layer embryo is formed, which contains the outer, middle and inner germ layers (ectoderm, mesoderm and endoderm) and a complex of axial organs (notochord, neural and intestinal tube). Next, tissues are formed from the germ layers - histogenesis, and organs are formed from tissues - organogenesis.

The type of gastrulation is determined by the type of egg. There are: 1) invagination, 2) epiboly (fouling), 3) immigration, 4) delamination (splitting). Humans and higher mammals are characterized by a mixed type with a predominance of immigration and delamination.

In the process of embryogenesis, critical periods are distinguished when factors of minimal strength can cause maximum changes in development. These periods include:

Progenesis (formation of germ cells);

Fertilization process;

Crushing:

Gastrulation;

Implantation (7-8 days);

Histogenesis;

Organogenesis;

Systemogenesis:

Placental (3-8 weeks)

The process of giving birth to a child.