Histological study of mammalian animal tissues. Study of issues of cytology, histology and embryology. Histological research in medicine

Histology studies animal fabrics; The study of plant fabrics is usually referred to as the anatomy of plants. Histology is sometimes called microscopic anatomy, since it studies the structure (morphology) of the body on the microscopic level (the object of histological examination is very thin tissue sections and individual cells). Although this science is primarily a descriptive, its task also includes the interpretation of the changes that occur in the tissues in the norm and pathology. Therefore, the histologist needs to be well able to create fabrics in the process embryonic developmentWhat is their ability to increase in the posthambrium period and what they are subject to change in various natural and experimental conditions, including during their aging and the death of the components of their cells.

Histology history as a separate branch of biology is closely related to the creation of a microscope and its improvement. M. Malpigi (1628-1694) is called the "father of microscopic anatomy", and consequently histology. Histology has been enriched with observations and methods of research conducted or created by many scientists, the main interests of which were in the field of zoology or medicine. This is evidenced by histological terminology that perpetuating their names in the names for the first time described by them structures or created methods: the islands of Langerhans, Libekyunovy gland, cochetic cells, Malpigayev layer, painting in Maksimov, painting by gimme, etc.

Currently, the methods of manufacturing preparations and their microscopic examination, which make it possible to study individual cells. Such methods include the technique of frozen sections, phase-contrast microscopy, histochemical analysis, tissue cultivation, electron microscopy; The latter allows you to study the cellular structures in detail (cell membranes, mitochondria, etc.). With the help of a scanning electron microscope, it was possible to identify the most interesting three-dimensional configuration of the free surfaces of cells and tissues that it is impossible to be seen under the usual microscope.

Many organs consist of tissues of several types, which can be recognized according to a characteristic microscopic structure. The following is a description of the main types of tissues found in all vertebrate animals. In the invertebrates, with the exception of sponges and shepherds, there are also specialized fabrics similar to the epithelial, muscular, connecting and nervous tissues of vertebrates.

A deeper understanding of regeneration and differentiation mechanisms will undoubtedly reveals many new opportunities for the use of these processes in therapeutic purposes. Fundamental studies have already made huge contribution In the development of skin transplant methods and cornea. In most differentiated tissues, cells that are capable of proliferation and differentiation are preserved, but there are tissues (in particular, the central nervous system in humans), which, being fully formed, are not capable of regeneration. Approximately at one-year-old central nervous system of a person contains the number of nerve cells, and although nerve fibers, i.e. Cytoplasmic processes of nerve cells are able to regenerate, cases of recovery of cells of the head or spinal cord, destroyed as a result of injury or degenerative disease, are unknown.

The classic examples of the replacement of normal cells and tissues in the human body is updating the blood and top layer of the skin. The outer layer of the skin - the epidermis - lies on a dense connectivecloth layer, the so-called. Derma, equipped with the smallest blood vessels delivering to her nutrients. The epidermis consists of a multilayer flat epithelium. The cells of its upper layers are gradually transforming, turning into thin transparent flakes - a process called by an energization; In the end, these scales are sent. Such a lunch is especially noticeable after severe sunburn skin. At the amphibians and resetting of the burned leather layer (molting) occurs regularly. The daily loss of surface skin cells is compensated at the expense of new cells coming from the actively growing lower layer of the epidermis. There are four layers of epidermis: the outer horny layer, under it - a brilliant layer (in which the orog begins, and its cells are becoming transparent), below - a grainy layer (pigment granules are accumulated in its cells, which causes skin darkening, especially under the action of solar The rays) and, finally, the deepest - reservoir, or basal, layer (in it throughout the body of the body, mitotic divisions occur, giving new cells to replace the lunches).

The human cells and other vertebrates are also constantly updated. Each type of cells is characterized by a more or less defined life expectancy, after which they are destroyed and removed from the blood by other cells - phagocytes ("cell eaters"), specially fit for this purpose. New blood cells (instead of collapsed) are formed in hematopoietic organs (in humans and mammals - in the bone marrow). If the loss of blood (bleeding) or the destruction of blood cells under the influence of chemicals (hemolytic agents) is caused by cellular damage blood populations, the blood-forming organs begin to produce more cells. With the loss of a large number of erythrocytes, supplying tissues with oxygen, body cells threaten oxygen starvation, especially dangerous for nervous tissue. With a lack of leukocytes, the body loses the ability to resist infections, as well as remove the collapsed cells from the blood, which in itself leads to further complications. Under normal conditions, the loss of blood serves as a sufficient incentive for mobilizing the regenerative functions of the blood-forming organs.

The cultivation of tissue culture requires certain skills and equipment, but this is the most important method of studying alive tissues. In addition, it allows you to obtain additional data on the status of tissues studied by conventional histological methods.

After fixing, the fabric is usually subject to dehydration. Since the rapid transfer to high concentration alcohol led to wrinkling and deformation of the cells, dehydration is gradually producing: the fabric is carried out through a number of vessels containing alcohol in a sequentially increasing concentration, up to 100%. After that, the fabric is usually transferred to a liquid that is well mixed with liquid paraffin; Most often, xylene or toluene is used for this. After short-term withstanding in xylene, the fabric is able to absorb paraffin. The impregnation is carried out in the thermostat so that the paraffin remains liquid. All this so-called Wiring is performed manually or put a sample into a special device that performs all operations automatically. The faster wiring using solvents (for example, tetrahydrofuran) can be mixed with water and paraffin.

After a piece of fabric is completely soaked with paraffin, it is placed in a small paper or metal shape and liquid paraffin adds to it, pouring them the entire sample. When paraffin hardens, it turns out a solid block with a cloth enclosed in it. Now the cloth can be cut. Usually for this use a special device - microtom. Tissue samples taken during the operation can be chopped, pre-freeze, i.e. Do not dehydration and fill in paraffin.

The procedure described above has to be somewhat modified if the cloth, such as bone, contains solid inclusions. Mineral bone components must be previously removed; For this, the fabric after fixation is treated with weak acids - this process is called decalcination. The presence in the block of bone that has not been subjected to decalcination, deforms all the fabric and damages the cutting edge of the microtome knife. It is possible, however, sawing the bone into small pieces and by calculating them with any abrasive, get the grinds - extremely thin bones suitable for studying under the microscope.

Microtome consists of several parts; The main ones are a knife and holder. The paraffin block is attached to the holder, which moves relative to the edge of the knife in the horizontal plane, and the knife itself remains fixed. After one slice is obtained, the holder with micrometric screws are promoted forward to a certain distance corresponding to the desired cut thickness. The thickness of the sections can reach 20 microns (0.02 mm) or to be only 1-2 microns (0.001-0.002 mm); It depends on the size of the cells in this tissue and usually ranges from 7 to 10 microns. Sections of paraffin blocks with a cloth enclosed in them are placed on the slide glass. Next, paraffin is removed, placing glass with cuts to xylene. If the fat components should be preserved in sections, then for filling the tissue instead of paraffin, carbovaks are used - synthetic polymer soluble in water.

After all these procedures, the drug is ready for staining - a very important stage of manufacturing histological preparations. Depending on the type of fabric and the nature of the study, different coloring methods apply. These methods, like the methods of filling tissue, were produced during many years of experiments; However, new methods are constantly being created, as associated both with the development of new areas of research and with the advent of new chemicals and dyes. Dyes serve as an important tool of histological examination due to the fact that they are absorbed in different ways with different tissues or their individual components (cellular nuclei, cytoplasm, membrane structures). The basis of staining is the chemical affinity between complex substancesincluded in the dyes and certain components of cells and tissues. Dyes are used in the form of aqueous or alcohol solutions, depending on their solubility and the selected method. After staining, the preparations are washed in water or alcohol to remove excess dye; After that, only those structures that absorb this dye will remain painted.

In order for the drug to continue for a sufficiently long time, the painted slice is covered with coating glass, smeared with some adhesive agent, which gradually solidifies. To do this, use Canadian balm (natural resin) and various synthetic media. Preparations in this way can be stored for years. To study tissues in an electron microscope, allowing to identify the ultrastructure of cells and their components, other fixation methods are used (usually using osphic acid and glutaraldehyde) and other fill media (usually epoxy resins). A special ultramicroth with a glass or diamond knife allows to obtain sections with a thickness of less than 1 μm, and the constant drugs are assembled not on the slide glasses, but on copper mesh. Recently, methods were created to apply a number of conventional histological staining procedures after the fabric was fixed and filling for electron microscopy.

For the labor-intensive process described herein, qualified personnel need, however, with mass production of microscopic drugs, they use conveyor technology in which many stages of dehydration, fill and even staining are made automatic instruments for tissue wiring. In cases where it is necessary to urgently diagnose, in particular during the surgical operation, the tissues obtained during biopsy are quickly fixed and frozen. Sections of such fabrics are manufactured in a few minutes, do not pour and immediately stain. An experienced pathomorphologist may, according to the total nature of the distribution of cells, immediately diagnose. However, for a detailed study, such cuts are unsuitable.

HISTOLOGY
Science engaged in the study of animal tissues. The fabric is called a group of cells similar in shape, sizes and functions and products of its livelihoods. All plants and animals, with the exception of the most primitive, the body consists of tissues, and at higher plants and highly organized animal animals are characterized by a large variety of structure and complexity of their products; Combining each other, different tissues form separate organs of the body. Histology studies animal fabrics; The study of plant fabrics is usually referred to as the anatomy of plants. Histology is sometimes called microscopic anatomy, since it studies the structure (morphology) of the body on the microscopic level (the object of histological examination is very thin tissue sections and individual cells). Although this science is primarily a descriptive, its task also includes the interpretation of the changes that occur in the tissues in the norm and pathology. Therefore, the histologist needs to be well able to form fabrics in the process of embryonic development, what is their ability to increase in the posthambrium period and what they are subject to change in various natural and experimental conditions, including during their aging and the death of the components of their cells. Histology history as a separate branch of biology is closely related to the creation of a microscope and its improvement. M. Malpigi (1628-1694) is called the "father of microscopic anatomy", and therefore histology. Histology has been enriched with observations and methods of research conducted or created by many scientists, the main interests of which were in the field of zoology or medicine. This is evidenced by histological terminology that perpetuating their names in the names for the first time described by them structures or created methods: the islands of Langerhans, Libekyunovy gland, cochetic cells, Malpigayev layer, painting in Maksimov, painting by gimme, etc. Currently, the methods of manufacturing preparations and their microscopic examination, which make it possible to study individual cells. Such methods include the technique of frozen sections, phase-contrast microscopy, histochemical analysis, tissue cultivation, electron microscopy; The latter allows you to study the cellular structures in detail (cell membranes, mitochondria, etc.). With the help of a scanning electron microscope, it was possible to identify the most interesting three-dimensional configuration of the free surfaces of cells and tissues that it is impossible to be seen under the usual microscope.
Origin of fabrics. The development of the embryo from the fertilized egg occurs in higher animals as a result of multiple cell divisions (crushing); The cells formed at the same time are gradually distributed in their places in different parts of the future embryo. Initially embryonic cells are similar to each other, but as their number increases, they begin to change, acquiring the characteristic features and the ability to perform certain specific functions. This process, called differentiation, ultimately leads to the formation of various tissues. All the fabric of any animal originate from three source germinal sheets: 1) of the outer layer, or ectoderma; 2) the inner layer, or entoderm; and 3) the middle layer, or mesoderm. For example, muscles and blood are derivatives of mesoderm, the lunk of the intestinal tract develops from the Entoderma, and the ectoderma forms the coating fabrics and the nervous system.
See also Embryology.

The main types of fabrics. Histologists are usually distinguished by four main fabrics in humans and higher animals: epithelial, muscle, connective (including blood) and nervous. In some tissues, the cells have about the same shape and dimensions and so tightly fit one to another, which is not left between them or almost the intercellular space remains; Such fabrics cover the outer surface of the body and linse its internal cavities. In other tissues (bone, cartilage), the cells are not so tight and surrounded by an intercellular substance (matrix), which they produce. From the cells of nervous tissue (neurons) forming the head and spinal cord, long processes are departed, ending with very far from the body of the cell, for example, in contact places with muscle cells. Thus, each cloth can be distinguished from others by the nature of the cell location. Some tissues are inherent in the sycitial structure, in which the cytoplasmic proceeds of one cells are transmitted to similar processes of neighboring cells; Such a structure is observed in a germinal mesenchym, loose connective tissue, reticular tissue, and may also occur in some diseases. Many organs consist of tissues of several types, which can be recognized according to a characteristic microscopic structure. The following is a description of the main types of tissues found in all vertebrate animals. In the invertebrates, with the exception of sponges and shepherds, there are also specialized fabrics similar to the epithelial, muscular, connecting and nervous tissues of vertebrates.
Epithelial fabric. Epithelium may consist of very flat (scaly), cubic or cylindrical cells. Sometimes it is multi-layered, i.e. consisting of several layers of cells; Such an epithelium forms, for example, the outer layer of the skin in humans. In other parts of the body, for example in the gastrointestinal tract, single-layer epithelium, i.e. All its cells are associated with the subject to basal membrane. In some cases, one-layer epithelium may seem multilayer: if the long axis of its cells are located non-parallel to each other, then the impression is that the cells are located at different levels, although they actually lie on the same basal membrane. Such an epithelium is called multi-row. The free edge of epithelial cells is covered with cilia, i.e. subtle hair-like protoplasm growth (such a paint epithelium sweeps, for example, the trachea), or ends with a "brush cut" (the epithelium, lining the delicate intestine); This carcake consists of ultramicroscopic finanted growth (so-called microvones) on the cell surface. In addition to the protective functions of the epithelium, it serves as a living membrane through which the absorption of gases and solutes is absorbed and their highlighting. In addition, the epithelium forms specialized structures, such as glands that generate the necessary organism of the substance. Sometimes secretory cells are scattered among other epithelial cells; An example can serve glassoid cells producing mucus, in the surface layer of skin in fish or in the intestinal lunches in mammals.

Blood. Blood is a completely special type of connective tissue; Some histologists even distinguish it into an independent type. The blood vertebrates consists of a liquid plasma and uniform elements: red blood cells, or erythrocytes containing hemoglobin; A variety of white cells, or leukocytes (neutrophils, eosinophils, basophils, lymphocytes and monocytes), and blood plates, or platelets. In mammals, mature red blood cells entering the bloodstream do not contain nuclei; All other vertebrates (fish, amphibians, reptiles and birds) mature red blood cells contain kernel. Leukocytes are divided into two groups - granular (granulocytes) and non-cristed (agranulocytes) - depending on the presence or absence of granules in their cytoplasm; In addition, they are not difficult to differentiate, using the painting with a special mixture of dyes: Eosinophil granules are purchased with such a staining bright pink color, cytoplasm of monocytes and lymphocytes - a bluish tint, basophilic granules - a purple shade, neutrophil granules - a weak purple tint. In the bloodstream, the cells are surrounded by a transparent liquid (plasma), in which various substances dissolved. Blood delivers oxygen into tissue, removes carbon dioxide and metabolic products from them, tolerate nutrients and secretion products, such as hormones, from some parts of the body to others. See also Blood.

What do we know about such science as histology? Indirectly with its main provisions could be found in school. But in more detail this science is studied at the Higher School (universities) in medicine.

At the level school program We know that there are four types of fabrics, and they are one of the basic components of our body. But people who plan to choose or have already chosen their profession a medical work, it is necessary to get acquainted in more detail with such a section of biology as histology.

What is histology

Histology is a science that studies the fabric of living organisms (person, animals and their other formation, structure, functions and interaction. This section of science includes several others.

As an academic discipline, this science includes:

• cytology (science studying cell);
• embryology (study of the process of development of the embryo, the characteristics of the formation of organs and tissues);
• common histology (science on the development, functions and structure of tissues, studies fabric features);
• private histology (studies the microstruses of the organs and their systems).

Levels of the organization of the human body as a holistic system

This hierarchy of the learning object of histology consists of several levels, each of which includes the subsequent. Thus, it is possible to visually submit it as a multi-level matriosk.

1. Organism. This is a biologically holistic system that is formed in the process of ontogenesis.
2. Organs. This is a set of fabrics that interact with each other by performing their main functions and ensuring the execution by the basic functions by the bodies.
3. Fabrics. At this level, cells are combined together with derivatives. Table types are studied. Despite the fact that they can consist of a variety of genetic data, their main properties determine the basic cells.
4. Cells. This level represents the main structural-functional unit of tissue - cell, as well as its derivatives.
5. Subcell level. At this level, the components of cells are studied - core, organelles, plasmolm, cytosol, and so on.
6. Molecular level. This level is characterized by the study of the molecular composition of cell components, as well as their functioning.

Science leaning fabrics: tasks

As for any science, a number of tasks are also allocated for histology, which are performed during the study and development of this field of activity. Among such tasks are the most important:

• study of histogenesis;
• interpretation of general histological theory;
• study of tissue regulation and homeostasis mechanisms;
• study of cell features such as adaptability, variability and reactivity;
• development of the theory of tissue regeneration after damage, as well as methods of substitution therapy of tissues;
• interpretation of the device of molecular genetic regulation, the creation of new methods as well as the movement of stem embryonic cells;
• studying the process of human development in the embryo phase, other periods of human development, as well as problems with reproduction and infertility.

Stages of the development of histology as science

As you know, the area of \u200b\u200bstudy of the structure of the tissue was called "Histology". What it is, scientists began to find out even before our era.

So, in the history of the development of this sphere, three main stages can be distinguished - the domindercopic (until the 17th century), microscopic (until the 20th century) and modern (up to today). Consider each of the steps more specifically.

Domikroscopic period

At this stage, histology in its initial form was engaged in such scientists as Aristotle, Nezali, Galen and many others. At that time, the object of study was fabrics that separated from the human body or animal by the preparation. This stage began in the 5th century BC and lasted until 1665.

Microscopic

The next, microscopic period began from 1665. Its dating is explained by the grand invention of the microscope in England. Scientist used a microscope to study various objects, including biological. The results of the study were published in the "Monograph" publication, where it was first used the concept of "cell".

Outstanding scientists of this period, studied fabrics and organs, were Marcello Malpigi, Anthony Wang Levenguk and Nehemia Grew.

The structure of the cell continued to explore such scientists as Yang Evangelist Purkinier, Robert Brown, Mattias Shleden and Theodore Schwann (his photo is placed below). The latter eventually formed which is relevant and up to today.

Such a science as histology continues to develop. What it is, at this stage is studying Camillo Golgi, Theodore Bovteri, Kit Roberts Porter, Christian Rene de Duel. Also, the relationship of work and other scientists, such as Ivan Dorofeyevich Chistyakov and Peter Ivanovich interleaving.

The modern stage of the development of histology

The last stage of science, studying tissues of organisms, starts from 1950. The time frame is defined as it is precisely then for the study biological objects An electron microscope was used for the first time, and new research methods were introduced, including the use of computer technologies, histochemistry and histoadography.

What is fabrics

Let us turn directly to the main object of studying such science as histology. Fabrics are an evolutionary cell system system and non-cellular structures that are combined due to the similarity of the structure and having common functions. In other words, the fabric is one of the components of the body, which is the combination of cells and their derivatives, and is the basis for the construction of internal and external human external organs.

The fabric consists not exclusively from the cells. The following components can include the following components: muscle fibers, sycyties (one of the stages of the development of genital cells), platelets, erythrocytes, hornbackers of the epidermis (postchalter structures), as well as collagen, elastic and reticular intercellular substances.

The appearance of the concept of "fabric"

For the first time, the concept of "fabric" was applied by the English scientist Nehemy GRU. We studied the tissues of plants, the scientist noticed the similarity of cell structures with textile fabric fibers. Then (1671 years) tissue and were described by such a concept.

Marie Francois Xavier Bisha, French Anatas, in his works even more firmly secured the concept of tissues. Varieties and processes in the tissues were also studied by Alexey Alekseevich Zavarzin (the theory of parallel rows), Nikolai Grigorievich Chlopin (the theory of divergent development) and many others.

But the first classification of tissues in this form, in which we know it now, was first suggested by German microscopists by Franz Leidig and Kelicker. According to this classification, tissue types include 4 main groups: epithelial (border), connecting (support-trophic), muscle (reduced) and nervous (excitable).

Histological research in medicine

Today, histology as a science studying tissue is very helping to diagnose the state of the internal organs of a person and the appointment of further treatment.

When a person diagnose suspicion for the presence of a malignant tumor in the body, histological examination is one of the first. This is essentially studying the sample of tissues from the patient's body obtained by biopsy, puncture, curethery, with the help of surgical intervention (excision biopsy) and other methods.

Thanks to the science, which studies the structure of the tissues, helps to assign the most correct treatment. In the photo above, you can consider the sample of trachea fabrics, painted by hematoxylin and eosin.

Such an analysis is carried out if necessary:

• confirm or disprove the diagnosed previously;
• establish an accurate diagnosis in the case when controversial issues arise;
• determine the presence of a malignant tumor in the early stages;
• observe the dynamics of changes in malignant diseases in order to prevent them;
• carry out the differential diagnosis of processes occurring in the bodies;
• determine the presence of cancer, as well as the stage of its growth;
• hold the analysis of changes occurring in tissues with already prescribed treatment.

Tissue samples are studied in detail under the microscope in the traditional or accelerated method. A traditional way more long, it is applied much more often. It uses paraffin.

But the accelerated method makes it possible to obtain the results of the analysis within an hour. This method is used when there is a need to urgently make a decision regarding the removal or preservation of the patient's body.

The results of histological analysis are usually the most accurate, since it is possible to study in detail the cells of the tissues for the presence of a disease, the degree of damage to the organ and methods of its treatment.

Thus, the science studying tissue makes it possible not only to explore the body, organs, tissues and cells of the living organism, but also helps to diagnose and treat hazardous diseases and pathological processes in the body.

Structural and functional elements Fabrics are divided into: histological elements cellular (1)and non-tossy type (2). The structural and functional elements of the tissues of the human body can be compared with different threads, of which textile fabric consist.

Histological preparation "Hyaline cartilage": 1 - Cells Chondrocytes, 2 - Intercellular substance (histological element of a non-boss)

1. Histological elements of cellular type Usually are alive structures with their own metabolism, limited by the plasma membrane, and are cells and their derivatives arising from the specialization. These include:

and) Cells - the main elements of the tissues that determine their main properties;

b) Postchalted structuresin which the most important signs for cells (core, organoids), for example: erythrocytes, hornbackers of epidermis, as well as platelets, which are parts of cells;

in) Symplasts - structures formed as a result of the fusion of individual cells into a single cytoplasmic mass with a plurality of nuclei and a common plasmolemma, for example: fiber of skeletal muscle tissue, osteoclast;

d) Sycytia - structures consisting of cells combined into a single network by cytoplasmic bridges due to incomplete separation, for example: spermatogenic cells at the reproduction stages, growth and ripening.

2. Histological elements of non-boss represented by substances and structures that are produced by cells and stand out beyond the limits of plasmolemm, combined under the general title "Intercellular substance" (fabric matrix). Intercellular substance Usually includes the following varieties:

and) Amorphous (main) substance – represented by the structureless accumulation of organic (glycoproteins, glycosocaminoglycans, proteoglycans) and inorganic (salts) substances between tissue cells in a liquid, gelling or solid, sometimes crystallized state (base tissue basic substance);

b) Fiber – Consist of fibrillar proteins (elastin, various types of collagen), often forming bundles of different thickness in the amorphous substance. Among them are distinguished: 1) collagen, 2) reticular and 3) elastic fibers. Fibrillar proteins also participate in the formation of cell capsules (cartilage, bone) and basal membranes (epithelium).

In the photo - the histological drug "loose fiber connecting fabric": the cells are clearly visible, between which the intercellular substance (fibers - strips, amorphous substance - bright areas between the cells).

2. Classification of tissues. In accordance with morphofunctional classification Tissue distinguish: 1) Epithelial fabrics, 2) fabrics interior environment: Connecting and bleeding, 3) muscle and 4) nervous fabric.

3. Tissue development. Theory of divergent development Fabrics by N.G. Chlopin suggests that the tissues arose as a result of divergence - discrepancies in connection with the adaptation of structural components to new operating conditions. Theory of parallel rows By A.A. The cauldron describes the causes of the evolution of tissues, according to which the fabric performing similar functions have a similar structure. In the course of phylogenesis, the same tissues occurred in parallel in different evolutionary branches of the animal world, i.e. Completely different phylogenetic types of initial tissues, falling into similar conditions for the existence of an external or inner medium, gave similar morphofunctional types of tissues. These types occur in philogenesis independently of each other, i.e. In parallel, in absolutely different groups of animals during the coherence of the same circumstances of evolution. These two complementary theory are combined into a single evolutionary tissue concept (A.A. Brown and P.P. Mikhailov), according to which similar tissue structures in various branches of the phylogenetic tree occurred in parallel during the divergent development.

How from one cell - zygota forms such a variety of structures? For this, these processes are responsible as determination, commitment, differentiation. Let's try to deal with these terms.

Determination- This is a process that determines the direction of development of cells, fabrics from embryonic incarnivers. During determination, the cells are able to develop in a certain direction. Already in the early stages of development, when crushing occurs, two types of blastomers appear: bright and dark. From light blastomers will not be able to subsequently for example, for example, cardiomyocytes, neurons, since they are determined and their direction of development - the epithelium of chorion. These cells are strongly limited to the possibilities (potency) develop.

Step, coordinated with the body's development program, restriction of possible ways of development due to determination is called comitation . For example, if the cells of the renal parenchyma can still develop from cells of the primary ectoderma in a two-layer embryo, then with the further development and formation of the three-layer embryo (ectoderma ectoderma) from the secondary ectoderma - only nervous fabric, skin epidermis and some other.

The determination of cells and tissues in the body, as a rule, irreversible: Mesoderm cells, which were evaporated from the primary strip to form the renal parenchyma, turn into cells in the primary ectoderma cells.

Differentiation aims to create in multicellular organism several structural and functional cell types. In humans of such types of cells, more than 120. During the differentiation, there is a gradual formation of morphological and functional signs of specialization of tissue cells (cellular type formation).

Differon - This is a histogenetic series of single-type cells located at different stages of differentiation. Like people on the bus - children, young people, adults, elderly. If the bus will be transported with kittens, then we can say that in the bus "Two Differona - People and Cats."

In the composition of the differentiation differon, the following cell populations distinguish: a) stem cells - the least differentiated cells of this tissue, capable of sharing and being the source of the development of its other cells; b) semi-mass cells- predecessors have limitations in the ability to form different types of cells, due to commitations, but are capable of active reproduction; in) cells - Blast, entered into differentiation but preserving the ability to divide; d) ripening cells - ending differentiation; e) mature(differentiated) cells that finish the histogenetic series, the ability to divide them, as a rule, disappears, in the tissue they are actively functioning; e) old cells - completed active functioning.

The level of cell specialization in Differon populations increases from stem to mature cells. At the same time, changes in the composition and activity of enzymes, cell organoids occur. For histogenetic series of differentials is characteristic the principle of irreversibility of differentiation. Under normal conditions, the transition from a more differentiated state to less differentiated is impossible. This property of Differon is often disturbed in pathological conditions (malignant tumors).

An example of differentiation of structures to form muscle fibers (sequential stages of development).

Zygote - Blastocyst - Inner Cell Mass (Embubline) - Epiblast - Mesoderma - unregulated Mesoderma - Somit - motoma cells Somomita - Mitotic myoblastics - myoblasts postmitic - muscular tube - muscular fiber.

In the diagram from the stage to the stage, the number of potential differentiation directions is limited. Cells non-gentle mesoderm Have the ability (potency) to differentiate in various directions and formation of miogenic, hondronogenic, osteogenic and other differentiation directions. Motoma cells Somitov Determined to development only in one direction, namely, to the formation of a miogenic cell type (cross-rope of a skeletal type muscle).

Cell populations - This is a combination of organism cells or tissues similar to any sign. According to the ability to self-renew the cell division, 4 categories of cell populations (by Leblon) are distinguished:

- Embryonal (Quickly divided by cell population) - all population cells are actively divided, specialized elements are absent.

- Stable The cell population is long-lived, actively functioning cells, which due to extreme specialization have lost the ability to divide. For example, neurons, cardiomyocytes.

- growing (labile) cell population - specialized cells which are able to share under certain conditions. For example, kidney epitheliums, liver.

- updating population It consists of cells, constantly and quickly divided, as well as specialized functioning descendants of these cells, the lifespan of which is limited. For example, intestinal epitheliums, blood-forming cells.

To the special type of cell populations referred clone - A group of identical cells originating from one sourceal predecessor cell. Concept clone As a cell population is often used in immunology, for example, a clone of T-lymphocytes.

4. Tissue regeneration - A process that ensures its update during normal life (physiological regeneration) or recovery after damage (reparative regeneration).

Cambial elements - These are the populations of stem, semi-union predecessor cells, as well as blast cells of this tissue, the division of which maintains the necessary number of its cells and fills the loss of the population of mature elements. In those tissues in which cell updates do not occur by dividing them, Cambier is absent. On the distribution of cambial elements of the tissue, several varieties of Cambia distinguish:

- Localized Cambier - its elements are concentrated in specific areas of the fabric, for example, in the multilayer epithelium of Cambius is localized in the basal layer;

- Diffuse Cambier - its elements are scattered in tissue, for example, in smooth muscular tissue, cambial elements are dispersed among differentiated myocytes;

- made by Cambier - Its elements lie outside the fabric and as differentiations are included in the composition of the fabric, for example, blood contains only differentiated elements, cambium elements are in the blood formation organs.

The possibility of tissue regeneration is determined by the ability of its cells to divide and differentiation or the level of intracellular regeneration. Well regenerate fabrics that have cambial elements or are renewable or growing cellular populations. The activity of dividing (proliferation) of cells of each tissue during regeneration is controlled by growth factors, hormones, cytokines, keylons, as well as the character of functional loads.

In addition to tissue and cell regeneration by dividing the cells intracellular regeneration - The process of continuous update or restoration of the structural components of the cell after damage. In those tissues that are stable cell populations and in which there are no cambial elements (nervous fabric, cardiac muscular fabric), this type of regeneration is the only possible way to update and restore their structure and function.

Hypertrophy fabric - an increase in its volume, mass and functional activity - is usually a consequence a) hypertrophy of cells (with them unchanged) due to reinforced intracellular regeneration; b) hyperplasia -an increase in the number of its cells by activating cell division ( proliferation) and (or) as a result of accelerating the differentiation of new-generated cells; c) combinations of both processes. Tissue atrophy - Reducing its volume, mass and functional activity due to a) atrophy of its individual cells due to the predominance of catabolism processes, b) the death of its cells, c) of a sharp decrease in the fission and differentiation of cells.

5. Front and intercellular relationship. The fabric maintains the constancy of its structural and functional organization (homeostasis) as a whole only under the condition permanent influence histological elements on each other (intricate interactions), as well as one tissues onto other (emercary interactions). These influences can be viewed as the processes of mutual recognition of elements, the formation of contacts and the exchange of information between them. At the same time, various structural and spatial associations are formed. Cells in fabrics can be at a distance and interact with each other through the intercellular substance (connecting tissues), in contact with the processes, sometimes reaching a significant length (nervous tissue), or to form tightly injecting cellular layers (epithelium). The combination of tissues combined into a single structural whole connective tissue, the coordinated functioning of which is provided by nervous and humoral factors, forms organs and systems of organs of the whole body.

For the formation of fabric it is necessary that the cells are combined and related to the cellular ensembles. The ability of cells is selectively attached to each other or the components of the intercellular substance are carried out using the recognition and adhesion processes, which are a prerequisite for maintaining the tissue structure. Reactions of recognition and adhesion occur due to the interaction of macromolecules of specific membrane glycoproteins, called name adhesion molecules. Attachment occurs with the help of special subcellular structures: a ) point adhesion contacts (attaching cells to the intercellular substance), b) intercellular compounds(attaching cells to each other).

Intercellular compounds - Specialized cell structures with which they are mechanically bonded between themselves, and also create barriers and permeability channels for intercellular communication. Distinguish: 1) adhesion cell compoundsperforming the function of the intercellular clutch (intermediate contact, desplaomomoma, half oftessomomomomoma), 2) Shutter contacts, whose function is the formation of a barrier, delaying even small molecules (tight contact), 3) conductive (Communication) ContactsThe function of which consists in transmitting signals from the cell to the cell (slit contact, synaps).

6. Regulation of tissue life. At the heart of the regulation of tissues - three systems: nervous, endocrine and immune. Humoral factors providing intercellular interaction in tissues and their metabolism include a variety of cellular metabolites, hormones, mediators, as well as cytokines and cailers.

Cytokines are the most versatile class of intra and interstitial regulators. They are glycoproteins, which in very low concentrations affect the reaction of cell growth, proliferation and differentiation. The action of cytokines is due to the presence of receptors to them on the plasmolymm of target cells. These substances are transferred with blood and have a distant (endocrine) effect, and also apply to the intercellular substance and operate locally (auto or paracryno). The most important cytokines are interleukins(IL), rost factors, colonsessulating factors (KSF), tumor necrosis factor (FLN), interferon. Cells of various tissues have a large number of receptors to a variety of cytokines (from 10 to 10,000 per cell), the effects of which are often interconnected, which ensures high reliability of the functioning of this intracellular regulation system.

Caleon - Hormone-like cell proliferation regulators: mitoses inhibit and stimulate cell differentiation. Caleeons operate according to the principle of feedback: with a decrease in the number of mature cells (for example, the loss of epidermis during injury) the number of cailers decreases, and the division of unoccalued cambial cells is enhanced, which is carried out to the tissue regeneration.

Histology (from Greek. Ίστίομ - Fabric and Greek. Λόγος - knowledge, word, science) - section of biology that studies the structure of fabrics of living organisms. This is usually done by dissemination of tissues on thin layers and using a microtoma. Unlike anatomy, histology studies the structure of the body in the tissue level. Human histology is a section of medicine that studies the structure of human tissues. Histopathology is a section of microscopic study of the affected tissue, is an important tool for pathological (pathological anatomy), since the exact diagnosis of cancer and other diseases usually requires histopathological research of samples. Histology forensic medical is a section of forensic medicine that studies the characteristics of the fabric levels.

Histology originated long before the invention of the microscope. The first descriptions of the tissues are found in the works of Aristotle, Galen, Avicenna, Kezalia. In 1665, R. Guk introduced the concept of the cell and observed the cellular structure of some tissues into the microscope. Histological studies were carried out by M. Malpigi, A. Levenguk, Ya. Swamemerdam, N. Grew, and others. A new stage of development of science is associated with the names of K. Wolf and K. Bair - the founders of embryology.

In the XIX century, histology was a full academic discipline. In the middle of the XIX century A. Köllic, Lyding, etc. created the foundations of modern teachings about the tissues. R. Virhov marked the development of cellular and tissue pathology. The discoveries in cytology and the creation of cell theory stimulated the development of histology. Proceedings of I. I. Minkov and L. Pasteur, formulated the main ideas about the immune system, were greatly influenced by the development of science.

The Nobel Prize of 1906 in physiology or medicine was awarded to two histologists, Camillo Golgi and Santiago Ramon-I-Kahalyu. They had mutually opposing views on the nervous structure of the brain in various considerations of the same snapshots.

In the XX century, the improvement of the methodology continued, which led to the formation of histology in its current form. Modern histology is closely related to cytology, embryology, medicine and other sciences. Histology develops issues such as patterns of development and differentiation of cells and tissues, adaptation at cellular and tissue levels, problems of tissue and organ regeneration, etc. Achievements of pathological histology are widely used in medicine, allowing you to understand the mechanism of developing diseases and suggest methods for their treatment.

The methods of research in histology include the preparation of histological preparations, followed by their study using a light or electron microscope. Histological preparations are strokes, penprints of organs, thin sections of body pieces, possibly painted with a special dye, placed on a microscope-based glass, enclosed in a preservative environment and covered with coated glass.

Histology fabric

The fabric is a phylogenetically established system of cells and non-cellular structures that have a common structure, often origin and specialized in performing specific specific functions. The fabric is laid in embryogenesis of embryonic leaves. From the ectithelmic skin epithelium (epidermis), the epithelium of the front and rear digestive channel (including respiratory tract epithelium), the epithelium of the vagina and urinary tract, the parenchyma of the large salivary glands, the outer epithelium of the cornea and the nervous fabric.

Messenchima and its derivatives are formed from the mesoderm. These are all the types of connective tissue, including blood, lymph, smooth muscular fabric, as well as skeletal and hearty muscle tissue, nephrogenic fabric and mesothelium (serous shells). From Entoderma - the epithelium of the middle department of the digestive channel and the parenchyma of the digestive glands (liver and pancreas). Fabrics contain cells and an intercellular substance. At the beginning, stem cells are formed - these are unoccupied cells capable of dividing (proliferation), they are gradually differentiated, i.e. They acquire the features of mature cells, lose the ability to divide and become differentiated and specialized, i.e. capable of performing specific functions.

The direction of development (cell differentiation) is due to genetically - determination. Provides this directivity of the microenvironment, the function of which performs the line of organs. The totality of cells that are formed from one type of stem cells - Differon. Fabrics form organs. In organs, they allocate stroma formed by connecting tissues, and a parenchyma. All fabric regenerate. There is a physiological regeneration that constantly flowing under normal conditions, and reparative regeneration, which arises in response to irritation of tissue cells. Regeneration mechanisms are the same, only reparative regeneration goes several times faster. Regeneration is based on recovery.

Regeneration Mechanisms:

By dividing the cells. It is especially developed in the earliest tissues: epithelial and connective, they contain many stem cells whose proliferation provides regeneration.

Intracellular regeneration - it is inherent in all cells, but is a leading mechanism for regeneration in highly specialized cells. The basis of this mechanism is the strengthening of intracellular metabolic processes, which lead to the restoration of the cell structure, and with further strengthening of individual processes

hypertrophy and intracellular organelle hyperplasia occurs. which leads to compensatory cell hypertrophy capable of performing a large function.

Origin fabrics

The development of the embryo from the fertilized egg occurs in higher animals as a result of multiple cell divisions (crushing); The cells formed at the same time are gradually distributed in their places in different parts of the future embryo. Initially embryonic cells are similar to each other, but as their number increases, they begin to change, acquiring the characteristic features and the ability to perform certain specific functions. This process, called differentiation, ultimately leads to the formation of various tissues. All the fabric of any animal originate from three source germinal sheets: 1) of the outer layer, or ectoderma; 2) the inner layer, or entoderm; and 3) the middle layer, or mesoderm. For example, muscles and blood are derivatives of mesoderm, the lunk of the intestinal tract develops from the Entoderma, and the ectoderma forms the coating fabrics and the nervous system.

Fabrics developed in evolution. 4 groups of tissues are isolated. The classification is based on two principles: histogenetic, which is based on the origin and morphofunctional. According to this classification, the structure is determined by the function of the tissue. The first arose epithelial or coating fabrics, the most important functions - protective and trophic. They differ in the high content of stem cells and is regenerated by proliferation and differentiation.

Then there are connective tissues or support and trophic, internal media fabrics. Leading functions: trophic, support, protective and homeostatic - maintenance of constancy of the inner medium. They are characterized by a high stem cell content and are regenerated by proliferation and differentiation. In this tissue, an independent subgroup is distinguished - blood and lymph - their tissues.

The following are muscular (contractile) fabrics. The main property is a contractile - determines the motor activity of the organs and the body. The smooth muscle tissue is isolated-dimensional ability to regenerate by the proliferation and differentiation of stem cells, and allocated (cross-striped) muscle tissues. These include cardiac tissue-cellular regeneration, and skeletal fabric is regenerated by the proliferation and differentiation of stem cells. The main recovery mechanism is intracellular regeneration.

Then the nervous fabric arose. Contains glial cells, they are capable of proliferating. But the nerve cells themselves (neurons) are highly differentiated cells. They react to stimuli, form a nervous impulse and transmit this impulse to the process. Nervous cells have intracellular regeneration. As the tissue differentiates, the leading method of regeneration is shown - from cell to intracellular.

Main types of fabrics

Histologists are usually distinguished by four main fabrics in humans and higher animals: epithelial, muscle, connective (including blood) and nervous. In some tissues, the cells have about the same shape and dimensions and so tightly fit one to another, which is not left between them or almost the intercellular space remains; Such fabrics cover the outer surface of the body and linse its internal cavities. In other tissues (bone, cartilage), the cells are not so tight and surrounded by an intercellular substance (matrix), which they produce. From the cells of nervous tissue (neurons) forming the head and spinal cord, long processes are departed, ending with very far from the body of the cell, for example, in contact places with muscle cells. Thus, each cloth can be distinguished from others by the nature of the cell location. Some tissues are inherent in the sycitial structure, in which the cytoplasmic proceeds of one cells are transmitted to similar processes of neighboring cells; Such a structure is observed in a germinal mesenchym, loose connective tissue, reticular tissue, and may also occur in some diseases.

Many organs consist of tissues of several types, which can be recognized according to a characteristic microscopic structure. The following is a description of the main types of tissues found in all vertebrate animals. In the invertebrates, with the exception of sponges and shepherds, there are also specialized fabrics similar to the epithelial, muscular, connecting and nervous tissues of vertebrates.

Epithelial fabric. Epithelium may consist of very flat (scaly), cubic or cylindrical cells. Sometimes it is multi-layered, i.e. consisting of several layers of cells; Such an epithelium forms, for example, the outer layer of the skin in humans. In other parts of the body, for example in the gastrointestinal tract, single-layer epithelium, i.e. All its cells are associated with the subject to basal membrane. In some cases, one-layer epithelium may seem multilayer: if the long axis of its cells are located non-parallel to each other, then the impression is that the cells are located at different levels, although they actually lie on the same basal membrane. Such an epithelium is called multi-row. The free edge of epithelial cells is covered with cilia, i.e. Thin hair-like protoplasm, such a fishing epithelium sweeps, for example, a trachea), or ends with a "brush cut" (epithelium, lining the delicate intestine); This carcake consists of ultramicroscopic finanted growth (so-called microvones) on the cell surface. In addition to the protective functions of the epithelium, it serves as a living membrane through which the absorption of gases and solutes is absorbed and their highlighting. In addition, the epithelium forms specialized structures, such as glands that generate the necessary organism of the substance. Sometimes secretory cells are scattered among other epithelial cells; An example can serve glassoid cells producing mucus, in the surface layer of skin in fish or in the intestinal lunches in mammals.

Muscle. Muscular fabric is different from the rest of its ability to reduce. This property is due to the internal organization of muscle cells containing a large number of submicroscopic contracting structures. There are three types of muscles: skeletal, also called transverse or arbitrary; smooth, or involuntary; Heart muscle, which is transverse, but involuntary. Smooth muscular fabric consists of spindle-shaped single-core cells. Transverse muscles are formed from multi-core elongated contractile units with characteristic transverse allocations, i.e. alternating light and dark stripes perpendicular long axis. The heart muscle consists of single-core cells, connected end to the end, and has a cross-aided; In this case, the contracting structures of neighboring cells are connected by numerous anastomoses, forming a continuous network.

Connective tissue. There are various types of connective tissue. The most important supporting structures of the vertebrate consist of a connective tissue of two types - bone and cartilage. Chickening cells (chondrocytes) highlight a dense elastic main substance (matrix). Bone cells (osteoclasts) are surrounded by a basic substance containing salts deposits, mainly calcium phosphate. The consistency of each of these tissues is usually determined by the character of the main substance. As the body agrees, the content of mineral deposits in the main bone substance increases, and it becomes more breaking. In young children, the main substance of the bone, as well as cartilage is rich in organic substances; Due to this, they usually have no real bone fractures, and so-called. Digits (fractures by the type of green branch). Tendons consist of fibrous connective tissue; Its fibers are formed from collagen - protein secreted by fibrocytes (tendon cells). Fat fabric is located in different parts of the body; This is a kind of connecting tissue, consisting of cells in the center of which is a large globule of fat.

Blood. Blood is a completely special type of connective tissue; Some histologists even distinguish it into an independent type. The blood vertebrates consists of a liquid plasma and uniform elements: red blood cells, or erythrocytes containing hemoglobin; A variety of white cells, or leukocytes (neutrophils, eosinophils, basophils, lymphocytes and monocytes), and blood plates, or platelets. In mammals, mature red blood cells entering the bloodstream do not contain nuclei; All other vertebrates (fish, amphibians, reptiles and birds) mature red blood cells contain kernel. Leukocytes are divided into two groups - granular (granulocytes) and non-cristed (agranulocytes) - depending on the presence or absence of granules in their cytoplasm; In addition, they are not difficult to differentiate, using the painting with a special mixture of dyes: Eosinophil granules are purchased with such a staining bright pink color, cytoplasm of monocytes and lymphocytes - a bluish tint, basophilic granules - a purple shade, neutrophil granules - a weak purple tint. In the bloodstream, the cells are surrounded by a transparent liquid (plasma), in which various substances dissolved. Blood delivers oxygen into tissue, removes carbon dioxide and metabolic products from them, tolerate nutrients and secretion products, such as hormones, from some parts of the body to others.

Nervous fabric. Nervous tissue consists of highly specialized cells - neurons concentrated mainly in the gray matter of the head and spinal cord. A long torque of neuron (axon) stretches over long distances from the place where the body of a nervous cell containing the kernel is located. The axons of many neurons form beams that we call nerves. Dendrites are also departed from neurons - shorter processes, usually numerous and branched. Many axons are covered with a special myelin shell, which consists of Schwann cells containing a hillock material. Neighboring Schwannsky cells are divided into small gaps, called Ranvier interception; They form a characteristic deepening on the Axone. Nervous tissue is surrounded by a special type with a supporting cloth known as neuroglia.

Tissue reactions for abnormal conditions

In case of damage to the tissues, some loss of the structure typical for them is possible as a reaction to the impairment.

Mechanical damage. With mechanical damage (cut or fracture), the tissue reaction is aimed at filling the resulting gap and reunite the edges of the wound. The weakly differentiated elements of the tissues, in particular fibroblasts, are fixed to the breakdown. Sometimes the wound is so great that the surgeon has to bring into it pieces of fabric in order to stimulate the initial stages of the healing process; For this purpose, fragments or even whole pieces of bones obtained during amputation and stored in the "Bone Bank" are used. In cases where the skin surrounding a greater wound (for example, in burns) cannot be healing, resort to healthy skin flap transfers taken from other parts of the body. Such transplants in some cases are not pressed, since the transplanted tissue does not always manage to form contact with those parts of the body to which it is transferred, and it dies or rejects the recipient.

Pressure. Omo-precipiency occurs with constant mechanical damage to the skin as a result of pressure rendered on it. They manifest themselves in the form of nice to all corns and thickens of the skin on the soles of the legs, hand palms and in other parts of the body experiencing constant pressure. Removing these thickens by excision does not help. As long as the pressure continues, the formation of coams will not cease, and we only expose the sensitive underlying layers, which can lead to the formation of a wound and the development of infection.