Malignant neoplasms are a group of diseases that includes several thousand types of tumors of different types and different degrees of malignancy. They are divided into large groups depending on what tissues they develop from: if from epithelial (barrier) tissues, then these are cancers, if from connective tissues (soft tissues and bones) - sarcomas, if from lymphoid (immune) - lymphomas / leukemias. The correctness and effectiveness of treatment depends on how correctly the tumor is verified (its type, degree of malignancy and other characteristics are determined). Histological studies play an important role in this.

The head of the pathoanatomical department with the prosectura of the National Medical Research Center of Oncology named after N.N. N.N. Petrova, Ph.D. Anna Sergeevna Artemyeva.

What is the material for pathomorphological (histological) studies?

A piece of patient tissue: skin, mucous membranes, internal organs, bones, brain and spinal cord, etc., the so-called biopsy.

The process of obtaining a tissue fragment (biopsy) - a biopsy - these are several different ways of taking material for histological examination.

Types of biopsy:

• Puncture biopsy - "poke", a thin or thick needle. Needle biopsies rarely have a diameter greater than 1-2 mm.
• Knife biopsy - open or endoscopic (minimally invasive), including laparothoraco-mediastinoscopy.

A biopsy of the internal organs is done under ultrasound navigation, or with the help of surgical intervention.

Surgical material is everything that is removed during the operation, as a rule, an organ or part of it, or several organs and / or parts of them with or without a formation (tumor).

How are these materials processed for histological examination?

Stage 1. Fixation - "preservation" of the biopsy in formalin - a special chemical solution that prevents decay, allows you to save tissue structures.

Fixing a biopsy can take from 6 to 24 hours, depending on its type and size.

The surgical material is fixed longer, in several stages. First, pre-fixation, which takes approximately 12 hours. Then cutting out the necessary fragments and re-fixation for another 24 hours.

The ratio of the volume of material to the volume of formalin should be 1:20.

Fixing time cannot be shortened!

Stage 2. Processing is the process of dehydration, degreasing and impregnation of the material with paraffin. The machine moves a piece of material from solution to solution.

The following are used as solutions: absolute isopropyl alcohol (6-8 shifts), xylene (2 shifts), molten paraffin (2 shifts).

The program differs for "fat" material (which includes, for example, breast tissue) and "non-fat" - 36 and 24 hours, respectively.

The process of obtaining paraffin blocks.

Stage 3. Making a paraffin block. A piece of material is placed in a mold with molten paraffin (already different than during processing - with a higher melting point) and cooled. It is done manually, it is difficult to speed up.

Microtomy

Stage 4. Slicing. The thickness of the sample - a piece of tissue embedded in paraffin - 1-3 mm. The thickness of each slice is 4-5 microns (0.004-0.005 mm). Performed by a laboratory assistant using a special tool - a microtome.

Sections are mounted on glass and must dry.

Despite the fact that part of the material is lost during alignment in a microtome, with due professionalism, it is possible to make about 100 slides (micropreparations) from one sample - material from one biopsy, surgical material from one tumor.

What are the cuts for?

Sections are made for routine hematoxylin and eosin staining, immunohistochemistry, and other types of studies.

The sections for all studies are the same, the color is different, the glasses on which they are mounted may differ, so special adhesive glasses or charged glasses are needed for IHC and FISH.

Histotainer

Blocks and slides can be stored for many years and used for additional histological studies, revisions, as well as for scientific purposes.

Archive

The archive of histological materials is collected at the N.N. N.N. Petrov since 1927 and contains more than 10 million items (micropreparations - glasses, paraffin blocks, archival cards, wet archive).

What types of histological studies are the most informative?

• Histological examination
• Immunohistochemistry (IHC)
• Fluorescent in situ hybridization (FISH), can be chromophobic (same principle, different label type)

What allow you to determine the different types of histological studies

Histological examination - what is it?

Allows you to verify the tumor - that is, to determine what cells it consists of (from what tissue it develops), the degree of its differentiation (maturity).

Routine staining, performed during histological examination, allows you to identify the pathological process in the analyzed material (biopsy, surgical material):

• inflammation,
• specific inflammation,
• developmental anomaly,
• tumor.

Also, in most cases, due to routine staining, it is possible to determine the degree of malignancy of the tumor and, if it is mature enough, then what is its nature.

Stained sections under a microscope

Invasive ductal carcinoma er 100%.	Carcinoma of the sigmoid colon.
Large cell neuroendocrine tumor.	MTS large cell neuroendocrine tumor.
Nonspecific breast cancer. Site of in situ carcinoma within the duct, cribriform type.	Poorly differentiated esophageal cancer.

Histological examination of the biopsy and surgical material can assess the prevalence: the size of the tumor and germination in the surrounding tissues, how affected the lymph nodes are, and whether there are metastases to distant organs (if all these structures were sent for histological examination). When consulting ready-made micropreparations - glasses, this is usually not possible if the tumor is larger than the size of the histological cassette or dissected by a previous researcher and macroscopic examination data are not provided.

During the histological examination, all glasses from one sample are studied - material obtained from one intervention - one operation or one biopsy, regardless of their number, this is considered one consultation.

The timing of the histological examination depends on the number of micropreparations and the category of complexity of the process that is found in them, the timing may be extended, especially if it is necessary to use additional research methods and analyze additional information. The timing of the histological examination is affected by the completeness of the clinical information provided by the patient, including the data of already conducted studies.

Immunohistochemistry (IHC)

A complex multi-stage study is performed after a histological examination on the same material. Tumor sections are stained with antibodies that are able to bind to antigens (proteins) carried by tumor cells. Different tumor cells carry different antigens, to each of which, like a key to a lock, an antibody fits.

One of the IHC stages

IHC research is combinatorics. 100% markers specific and sensitive to a certain tumor do not exist, but there is a set of antigens that should be in a certain type of tumor and a set of those that should not be there, so the IHC panel is built so as to include several antibodies that should be positive and a few that must be negative. These sets of positive/negative markers differ for different tumors.

When conducting prognostic IHC - identifying markers of sensitivity to therapy, a set of such markers for specific tumors, for example, breast cancer, is determined: steroid hormone receptors (estrogen, progesterone), epidermal growth factor receptor (HER2) and index of proliferative activity Ki67 (cell division rate) .

The slides are stained sequentially - sets of markers are stained with different antibodies in several stages, the process of staining slides with one antibody takes 48 hours.

Thus, each antibody is applied to a separate tissue section mounted on a separate glass, usually with appropriate external control, the number of reactions (antibodies used) and staining steps can vary significantly depending on the specific diagnostic situation, it all depends on the individual characteristics of the tumor. Such a number of stains is carried out, which is necessary in order to identify the most characteristic set of positive and negative markers for a particular tumor.

For someone, 5 antibodies will be enough for this, and someone needs to make 20 or more stains. The maximum number of colors that we had to do is 212.

Therefore, the exact timing and cost of this study cannot be determined in advance. Tumors of different course and prognosis can be very similar to each other, only minimal differences in staining, taking into account clinical data and data from other examination methods, can make it possible to establish the correct diagnosis.

There are a number of benign tumors that mimic malignant ones, including highly aggressive ones, and some highly differentiated malignant tumors are difficult to distinguish from inflammatory and reactive processes. In such situations, only the experience and qualifications of the pathologist, analysis of the entire range of available information (CT scans, MRI, x-rays, operation protocol, etc.) allow a diagnosis to be made.

In the competent interpretation of the IHC results, the role of an expert is very important, because the cases that you have to work with are, for the most part, complex. There are practically no antibodies that can act as 100% markers of a particular tumor, the doctor always has to weigh various probabilities.

What is determined by IHC?

• The presence of receptors for the hormones progesterone and estrogen in breast cancer;
• Expression of HER-2/neu in cells in breast cancer, stomach cancer;
• To determine Hodgkin's and non-Hodgkin's lymphomas - to establish an accurate diagnosis of lymphoma today is impossible without the use of this type of study.
• Determine whether it is a primary tumor or metastases, tissue affiliation of metastases.

Immunohistochemistry makes it possible to assess the potential growth rate of the tumor, the response to chemo-, targeted, hormonal therapy.

Fluorescent in situ hybridization (FISH test)

This is a method of molecular genetic diagnostics in tissue.

FISH is carried out in a tissue section and allows you to bind a genetic rearrangement to a specific tumor cell.

This test also uses special dyes that only bind to certain regions of chromosomes. They are called probes, which can be labeled with a fluorescent or chromogenic dye, visualized using a fluorescent or light microscope.

Technical operations for the preparation of histological slides for this study takes 2 working days.

Analysis of the preparation using a multihead microscope.

The resulting micropreparations are very sensitive to the external environment - they can fade over time, in order to avoid loss of information, all FISH slides are scanned, their digital copy is created, which is available for external review. Experts view the fluorescent material in a dark field, at least 2 specialists take part in the analysis of the drug. If necessary, digital analysis is also used.

What is determined by the FISH test?

FISH-test will allow to diagnose some types of tumors, determines the appropriateness of the use of certain chemotherapy drugs.

• the presence of HER2 amplification is determined in cases of borderline results according to IHC, which is necessary for the appointment of targeted therapy;
• diagnostics is carried out, that is, the identification of genetic rearrangements specific to a certain type of tumor, when it is impossible to finally establish a diagnosis using simpler methods, most often these are soft tissue sarcomas and brain tumors;
• genetic abnormalities that cause cancer of a particular organ;
• in lymphomas, this technique is used for diagnostic purposes and to identify factors of poor prognosis, that is, indications for early intensification of treatment.

Conducting a histological examination, and first of all a FISH test, is an expert work that depends on the qualifications of a specialist. Very many mutations that are detected in tumors are not always tumor markers; they can also be found in benign formations or normal tissues.

For a year, the pathoanatomical department of the National Medical Research Center of Oncology named after N.N. Petrova performs about 20,000 histological studies (patients), of which about 5,000 consultative cases (revisions), more than 30,000 IHC studies, and also participates in the NordIQ IHC external quality control program.

The specialists of the department have vast experience in conducting histological studies and expert competencies.

Remember! Histological studies are the starting point, the accuracy of the diagnosis and the effectiveness of the prescribed treatment depend on how well they are performed.

The speed of histological studies and the adequacy of the histological conclusion depend on a number of factors:

• Quality of glasses and blocks;
• Completeness of providing glasses (it is necessary to provide all glasses and blocks);
• Providing the patient with additional information that will help to correctly interpret the data of the histological examination, IHC and FISH test, namely: data on the history of the disease, data on concomitant diseases, primarily infectious (HIV, hepatitis); all the data of all examinations and interventions: X-rays, CT, MRI, ultrasound, protocols of operations, extracts.

After performing a histological examination, the patient receives a histological conclusion / protocol for the study of histological material.

Deciphering the histological examination: what to look for?

The histological conclusion includes several headings (fields):

Macroscopic description

It is filled in both for biopsy specimens - not necessarily, and for surgical material, for which it is extremely important in some cases.

Microscopic description

Description of changes at the microscopic level, not mandatory, since all the necessary information can be reflected in the "conclusion" field.

Results of the immunohistochemical study

This field describes what antibodies were used in this case and what the staining result was: presence of staining or not, localization in the cell if necessary, as well as the percentage of positive cells and the intensity of the reaction, when it matters.

Pathological anatomical conclusion

It contains a nosological / classification unit, if it is possible to establish it according to the studied material, that is, it gives answers to the questions:

• Is it a primary tumor or a metastasis?
• Where is the primary tumor located?
• What is the histological type of the tumor (what type of cells does it consist of).

All the necessary prognostic data are also given: the degree of differentiation, parameters affecting the stage, the state of the resection margins, if it is possible to evaluate them, etc.

The field may contain comments regarding the possible direction of further examination, the likelihood of a particular diagnosis, the need to familiarize yourself with certain clinical data, etc.

We do not recommend that patients independently decipher the parameters of histological examination using information obtained from various Internet sites and patient forums, since a large number of factors affect the interpretation of the data, including the patient's age, data from other studies, etc.

Only a specialist can deal with deciphering the study - an oncologist according to the profile of the disease!

What do you need to do

1. If you want to learn more about the free opportunities of the FBGU National Medical Research Center of Oncology named after N.N. N.N. Petrov of the Ministry of Health of Russia, get a full-time or correspondence consultation on diagnosis and treatment, make an appointment, read the information on the official website.
2. If you want to communicate with us through social networks, pay attention to the accounts in

The main research method in histology is microscopy - the study of histological preparations under a microscope. Recently, microscopy has been combined with other methods - histochemistry and historadiography. For microscopy, various designs of microscopes are used, which allow studying various parameters of histological preparations.

The following types of microscopy are distinguished:

1) light microscopy (the most common type of microscopy, while the resolution of the microscope is 0.2 microns);

2) ultraviolet microscopy (resolution of the microscope is 0.1 microns);

3) luminescent microscopy (used to determine certain chemical structures in the histological specimen under study);

4) phase-contrast microscopy (used to detect and study certain structures in unstained histological preparations);

5) polarizing microscopy (used mainly to study fibrous structures);

6) dark field microscopy is used to study living objects;

7) incident light microscopy (designed to study thick objects);

8) electron microscopy (the most modern type of microscopy with a resolution of 0.1 - 0.7 nm). There are two types of electron microscopy - transmission (transmission) and scanning (or solution) microscopy, which gives an image of surface ultrastructures.

Histological and cytochemical methods are used to determine the composition of chemicals and their amount in certain structures. The principle of the method lies in the chemical reaction between the reagent and the substrate contained in the test substance. In this case, the resulting reaction by-products can be detected using light or luminescent microscopy.

The method of histoautoradiography makes it possible to reveal the composition of chemicals in the structures under study and the intensity of the exchange by the inclusion of radioactive isotopes. This method is most often used in animal experiments.

The interferonometry method makes it possible to determine the dry mass of a substance in living or fixed objects.

The cell culture method is the cultivation of cells in test tubes or in special capsules in the body and the subsequent examination of living cells under a microscope.

The method of vital staining is the introduction of a dye (trepan blue) into the blood or into the abdominal cavity of the animal, which during the life of the animal is captured by certain cells - macrophages, and after the slaughter of the animal and the preparation of the preparation, the cells containing the dye are determined and counted.

Immunomorphological methods allow using preliminary immune reactions (based on antigen-antibody interaction) to determine the subpopulation of lymphocytes, the degree of foreignness of cells, to carry out histological typing of tissues and organs, i.e., to determine their histocompatibility for further transplantation.

The method of differential centrifugation is the study of individual organelles or even their fragments isolated from the cell. To do this, a piece of the organ under study is rubbed, filled with saline, and then dispersed in a centrifuge at various speeds (from 2 to 150 thousand per 1 min). As a result of centrifugation, fractions of interest are obtained, which are then studied by various methods.

Methods of morphometry - quantitative methods. They allow you to determine the size and volume of the nucleus - karyometry, cells - cytometry, organelles - electronic morphometry, as well as determine the number of cells of various populations and subpopulations. These methods are widely used in scientific research.

Various experimental methods - food and water load, physical methods (UHF, microwave, lasers, magnets). They are used to study the reaction of structures of interest to a particular impact and are combined with the methods of morphometry, cyto- and histochemistry. These methods are also used in scientific research.

Thus, the main and most common method of study in histology is microscopy. Preparation of a histological preparation includes the following steps.

Taking material

- piece of tissue or organ. When taking material, the following rules must be observed:

1) sampling should be carried out as soon as possible after the death or slaughter of the animal, if possible from a living object, in order to preserve the structure of the cells under study as best as possible;

2) the sampling of the material should be carried out with a sharp instrument so as not to injure the tissues;

3) the thickness of the piece should not exceed 5 mm so that the fixing solution can penetrate the entire depth of the tissue;

4) it is necessary to mark the piece, indicating the name of the body, the number of the animal or the name of the person, the date of sampling.

Material fixation

This stage is carried out in order to stop the metabolic processes in the cell and save it from decay. To do this, a piece of tissue taken for examination is immersed in a fixing solution. The solution can be simple (alcohol or formalin) and complex (Carnoy's solution, Zinker's fixative). The fixative causes protein denaturation and keeps the cell structure in a state close to life. Fixation can also be carried out by freezing - cooling with liquid nitrogen or a jet of carbon dioxide.

Pouring fabric pieces into sealing media

(paraffin, resins) - or freezing. This stage is necessary so that in the future a thin section can be made from the tissue under study.

Preparation of sections on a microtome or ultramicrotome using special knives

After that, sections for light microscopy are glued to glass slides, and for electron microscopy, they are mounted on special grids.

Section staining or contrasting

(for electron microscopy). Before staining the sections, it is necessary to remove the sealing medium - perform deparaffing. With the help of coloring, the contrast of the studied structures is achieved. Dyes can be divided into basic, acidic and neutral. The most widely used basic dyes (hematoxylin) and acidic (eosin). Complex dyes are also often used.

Section clearing in xylene and toluene

They are encapsulated in resins (balm and polystyrene) and covered with a coverslip.

After these procedures, the drug can be examined under a light microscope. Light microscope sections placed under glass can be stored for a long time and reused. For electron microscopy, each section is used only 1 time, while it is photographed, and the study of tissue structures is carried out according to the electron diffraction pattern.

If the tissue has a liquid consistency (for example, blood, bone marrow), then the preparation is made in the form of a smear on a glass slide, which is then also fixed, stained and studied.

From brittle parenchymal organs, preparations are made in the form of an organ imprint, this organ is fractured, then a glass slide is applied to the fracture site, on which free cells are glued. After that, the drug is fixed and studied.

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

Research methods in histology, cytology and embryology Part I Candidate of Medical Sciences, Senior Lecturer M.R. Grineva Doctor of Medical Sciences, Professor S.Yu. Vinogradov Doctor of Medical Sciences, Professor S.V. Dindiaev Ivanovo State Medical Academy Department of Histology, Embryology and Cytology more

Table of contents Introduction Methods for the study of living cells and tissues Types of histological preparations of fixed cells Preparation of a histological preparation Histological preparation Sampling Material fixation Material compaction Preparation of sections Polarizing microscopy Phase contrast microscopy Fluorescent (luminescent) microscopy Electron microscopy

Introduction In modern histology, cytology and embryology, a variety of research methods are used to comprehensively study the processes of development, structure and function of cells, tissues and organs. The main stages of cytological and histological analysis are the choice of the object of study, preparing it for microscopy, preparing it for microscopy, the use of microscopy methods, the use of microscopy methods, qualitative and quantitative analysis of the image. The objects of study are histological preparations made from living or fixed cells.

Methods for studying living cells and tissues more Studying living cells and tissues allows you to get the most complete information about their life activity - to trace the processes of movement, division, destruction, growth, differentiation and interaction of cells, the duration of their cell cycle, reactive changes in response to the action of various factors. Methods Live in the body (in vivo) Live in cell and tissue culture (in vitro) Implantation of transparent chambers Live microscopy Transplantation Suspension cultures Monolayer cultures In vivo cultivation back to contents

Types of histological preparations of fixed cells Smear Imprint Section Blood film of red bone marrow CSF saliva Vaginal and other spleen thymus liver bladder mucosa buccal mucosa and others peritoneum pleura pia mater connective tissue, etc. ) semi-thin (thickness less than 1 µm) ultra-thin (thickness less than 0.1 µm)

Histological preparation more Histological preparationsHistological preparations, as a rule, are sections (5-15 µm thick) of organs, tissues or cells stained with special histological dyes. The histological preparation must meet the following requirements: maintain the vital state of the structures; be thin and transparent enough to be studied under a microscope in transmitted light; be contrast, that is, the structures under study should be clearly defined under a microscope; preparations for light microscopy should be stored for a long time and used for re-examination. The process of making a histological preparation includes the following main steps: 1. Taking and fixing the material Taking and fixing the material 2. Sealing the material Sealing the material 3. Preparation of sections Preparation of sections 4. Staining of sections Staining of sections 5. Enclosing sections in a transparent medium Enclosing sections in a transparent medium back

Sampling of material The production of a histological preparation is made from organs and tissues obtained in several ways: biopsy (puncture), surgically, sectional (cadaveric) material, experimental. The following points should be taken into account: 1. Sampling of material should be carried out as soon as possible after death or slaughter experimental animal, and if possible from a living object (biopsy), so that the structures of the cell, tissue or organ are better preserved. 2. The sampling of pieces should be done with a sharp instrument so as not to injure the tissue. 3. The thickness of the piece should not exceed 5 mm so that the fixing solution can penetrate into the thickness of the piece. 4. The piece must be marked (indicate the name of the body, the number of the animal or the name of the person, the date of sampling, and so on). back next

Back fixation of the material The purpose of material fixation is to preserve the intravital morphology of cells and tissues, to prevent autolysis and post-mortem changes. The fixative causes protein denaturation and lipid stabilization and thereby suspends metabolic processes and preserves structures in their lifetime state. Fixation is achieved most often by immersing the piece in fixing liquids, which can be simple (formalin, alcohols, glutaraldehyde, acetone) and complex (Carnoy's solution, Zenker's fixative, etc.). Fixation can also be achieved by freezing (cooling in a CO 2 jet, liquid nitrogen, etc.). The selection of fixators and the duration of fixation is individual for various organs and tissues and usually ranges from 2 to 24 hours. table of contentsnext

Densification of the material back The purpose of this step is to give the test material such a density that allows you to get thin sections of the required thickness. This is achieved in two ways: Freezing the sample, followed by cutting on a freezing microtome. Impregnation with sealing media (paraffin, epoxy resins, etc.) The main stages of paraffin wiring: Rinsing the material with running tap water to remove the fixative. Dehydration (dehydration) of the material in alcohols of increasing concentration (70, 80, 90, 96, absolute - 100%). Removal of alcohol and preparation of material for impregnation with paraffin by treatment with solvents of paraffin (xylene, etc.) and a mixture of paraffin and xylene (at a temperature of 37°C). Paraffin cooling and block formation. table of contentsnext

Preparation of slices back For the manufacture of thin sections of a given thickness, special devices are currently used - microtomes (for light microscopy) and ultramicrotomes (for electron microscopy). µm from material frozen in the chamber of a microtome-cryostat 0.08-0.1 µm from material prepared for electron microscopy The resulting sections are placed on glass slides (for light microscopy) or mounted on special grids (for electron microscopy). table of contentsnext

Types of microtomes rotational cryostat sledge freezing for express diagnostics, histochemistry production of serial paraffin sections production of paraffin sections production of sections at a temperature of -20°C and below for histochemistry and immunocytochemistry vibrotome production of sections of fixed and non-fixed tissues back next

Staining of sections Cellular structures without special processing, as a rule, are not distinguishable even at high magnification of the microscope. They are colorless and transparent. To identify tissue components, individual cells, intracellular structures, dyes are used - substances with a high affinity for various tissue components and with certain color-optical properties. Dyes The ability of tissue components to stain differently depends on the acid-base (alkaline) properties of the substances that make up their composition . Before staining, the sections are deparaffinized by successively passing through a paraffin solvent (xylene), alcohols of descending concentration (100, 96, 90, 80, 70%) and placed in water. contents backnext

Special Staining Methods General histological table of contentsback ImpregnationHistochemical identification of the general plan of the structure of cells, tissues, organs identification of specialized structures in cells and tissues analysis of the chemical composition of cells and intercellular substance identification of specialized structures in cells and tissues more

Back impregnation A method for revealing tissue structures by impregnating objects of histological examination with salt solutions of heavy and precious metals (for example, silver nitrate (silver plating), cobalt, gold chloride (gold plating), cadmium, osmium anhydride, etc.). Tissue areas where metal salts are deposited on histological structures acquire a black or brown color depending on the amount and properties of the reduced metal. table of contents Peripheral nerve (transverse section). Osmium oxide impregnation Multipolar neuron. Silver nitrate impregnation Multipolar neurons. Silver nitrate impregnation more

Basic acidic neutral bases, binding with acidic compounds of histological structures, usually cause their staining in blue-violet colors, connecting with basic (alkaline) compounds of histological structures, stain them in the colors of the dye contain both basic and acidic coloring components basophilia neutrophilia metachromasia oxyphilia Types of general histological stains backcontentsnext

Basophilia Basic (alkaline) dyes actively bind to structures that contain acids and carry a negative charge - for example, DNA, RNA. These include, in particular, hematoxylin, toluidine blue, thionine, methylene blue, azure, etc. The ability to stain with basic (alkaline) dyes is called basophilia (from the Greek. basis - base and philia - love). basophilia Therefore, the structures that bind these dyes are called basophilic. In a cell, the nucleus has basophilia (due to the high content of DNA and RNA), sometimes the cytoplasm (with a high content of ribosomes or granular EPS in it). The intercellular substance of some tissues, for example, cartilage, can stain basophilically. contents backnext Basophilia of the nucleus of a neutrophilic granulocyte. Coloring according to Romanovsky-Giemsa. Magnification: x630.

Metachromasia Metachromasia (from the Greek. meta - change and chroma - color, paint) - a change in the color of some basic dyes when they are bound to structures with specific chemical properties (usually a high concentration of sulfated glycosaminoglycans). These dyes include toluidine blue, azure II, thionine, etc. Granules of basophilic leukocytes and mast cells have the ability to stain metachromatically. These dyes stain other basophilic structures in the same tissues in their usual color, i. orthochromatically (from the Greek orthos - correct and chroma - paint). contents backnext Metachromasia of granularity of basophilic granulocyte. Coloring according to Romanovsky-Giemsa. Magnification: x630.

Oxyphilia Acid dyes bind to positively charged structures such as proteins. These dyes include eosin, orange G, erythrosin, picric acid, etc. The ability to stain with acid dyes is called oxyphilia, or acidophilia (from Greek oxys or Latin acidus - sour and Greek philia - love). Oxyphilia Structures that bind these dyes are called oxyphilic or acidophilic. Oxyphilia is characteristic of the cytoplasm of cells (especially with a high content of mitochondria and some protein secretory granules in it), erythrocytes (due to the high concentration of hemoglobin in them). The cytoplasm of cardiomyocytes, muscle fibers of skeletal muscles, some components of the intercellular substance (for example, collagen fibers) are stained oxyphilically. contents backnext Oxyphilia granularity of eosinophilic granulocyte. Coloring according to Romanovsky-Giemsa. Magnification: x630.

Neutrophilia Neutrophilia (from Latin neutrum - neither one nor the other, and philia - predisposition, love) - the ability of histological structures to be stained with both acidic and basic dyes. contents backnext Neutrophilia is the granularity of a neutrophilic granulocyte. Coloring according to Romanovsky-Giemsa. Magnification: x630.

Conclusion of sections in a preservative medium back Stained histological preparations are dehydrated in ascending alcohol concentrations (70, 80, 90, 96, absolute - 100%) and clarified in xylene, benzene, toluene or some oils. For long-term storage, a dehydrated histological section is enclosed (mounted) in a transparent preservative medium (coniferous resin - Canadian, fir balsam, as well as in synthetic media). On a permanent histological preparation, the tissue section is located on a glass slide, covered from above with a coverslip. Between the glasses (subject and cover) there is a casting medium with a refractive index of light rays close to that of glass. table of contentsnext

Light microscopy more The study of a histological preparation is carried out in transmitted light using a light microscope. light microscope Light source natural or artificial (various lamps). The light is collected in a condenser and then directed through the preparation into the lens. The eyepiece further magnifies this image. the minimum (resolving) distance at which the optics of a microscope makes it possible to distinguish separately two closely spaced points. This value is proportional to the wavelength of the light and for a conventional light microscope is approximately 0.2 µm. The smaller the resolving distance, the higher the resolution of the microscope and the smaller objects can be examined. The magnification of a microscope is the ratio between the true dimensions of the object under study and the dimensions of its image obtained using a microscope. Roughly, it is estimated as the product of the magnifications of the lens and the eyepiece and can reach 2500 times. lenseyepiece contentsback

Light microscope device 1. Microscope base 2. Tube holder 3. Tube 4. Eyepiece (usually ×7) 5. Microscope revolver 6. Objectives a) dry: ×8, ×20, ×40 b) immersion ×90 7. Subject table 8 .Condenser 9.Macrometer screw 10.Micrometer screw 11.Condenser screw 12.Mirror Microscope total magnification = objective magnification × eyepiece magnification

Microscopy Technique 1. Microscopy of a histological preparation begins with proper lighting. To do this, with the help of a concave mirror that collects a scattered beam of light and a condenser, uniform illumination of the field of view is achieved. 3. The study of the histological preparation is started at a low magnification (x8 objective), while the distance between the objective and the cover slip should be about 1 cm. The sharpness is set using a macro screw. subject table. 5. Install a portion of the histological preparation in the center of the field of view, which should be studied at a high magnification (x40 objective). High magnification 6. Using a revolving device, a lens with a higher magnification (x40) is placed. Sharpening is carried out using a microscrew. Revolving device blood screw 7. To study very small histological structures, an immersion lens (x90) is used. Immersion lens A drop of immersion oil is applied to the cover glass of the preparation. Carefully lower the tube until the objective lens touches the oil. The sharpness setting is carried out with the help of a microscrew.Microscrew After the end of work, the immersion oil is removed from the objective and the coverslip with gauze. back next

Microscopy technique (examples) contentsback Kidney. Stain: hematoxylin-eosin. Magnification: x 56 (low magnification). Bud. Stain: hematoxylin-eosin. Magnification: x 280 (high magnification). Bud. Stain: hematoxylin-eosin. Magnification: x 630 (immersion magnification). Further

Dark-field microscopy back Based on the use of a special condenser that illuminates the specimen with "oblique" rays that do not fall into the objective. When there is an object in the field of view, the light is reflected from it and directed into the lens. The method is often used to study living unstained cells. table of contentsnext

Polarizing microscopy back Allows you to detect birefringence - anisotropy. A polarized beam of light is directed to the object of study, i.e. rays of light are directed strictly in one plane. This is provided by a special filter - a polarizer. Such light is directed to the object of study. The second filter - the analyzer is located between the objective and the eyepiece and allows you to register the angle of deviation of the light polarization plane. Microscopy allows you to register the spatial arrangement of molecules in the lens or crystal structures. contents Crystals of oxalates. polarizing microscopy. Zoom x100 further

Phase-contrast microscopy back This method is used to obtain contrast images of transparent and colorless objects, in particular, it allows studying live unstained preparations. Even with very small differences in the refractive indices of different elements of the drug, the light wave passing through them undergoes different changes in phase (acquires a phase relief). These phase changes, which are not perceived by the eye, are converted by a special optical device (the annular diaphragm in the condenser and the phase plate in the lens) into changes in the amplitude of the light wave, i.e. into changes in brightness (“amplitude relief”), which are already distinguishable by the eye. In other words, in the resulting visible image, the distribution of brightness (amplitudes) reproduces the phase relief. The resulting image is called phase contrast. contents Rat testicles. Unstained preparation. Phase contrast Rat testicles. Staining: hematoxylin-eosin Light microscopy Pseudotrichonympha grassi. Unstained preparation. Phase contrast next

It uses the principle of glowing the object of study when it is illuminated with ultraviolet rays. The light source is a special lamp. There is autofluorescence - own or primary fluorescence. For example, the glow of elastic fibers in the wall of arteries. Secondary fluorescence occurs after treatment of preparations with special dyes - fluorochromes (acridine orange, rhodamine, fluorescein, etc.). For example: after treatment with acridine orange, nuclear DNA (bright green glow) and RNA (bright red glow) are very clearly detected in the cell. After tissue fixation in formaldehyde vapors (Falck method), a bright green glow of serotonin, catecholamines (adrenaline, norepinephrine) is detected. Acridine orange Falk method If fluorescent dyes are associated with specific antibodies, their antigens can be detected. This method is called immunocytochemical. Immunocytochemical Fluorescent (luminescent) microscopy backcontentsnext

Fluorescent (luminescent) microscopy (examples) Eukaryotic cytoskeleton (bovine endothelial cells). Immunocytochemical staining method. Actin microfilaments are stained in red, microtubules in green, cell nuclei in blue. back.... Nucleic acids in the epithelium of the uterine glands. Stained with acridine orange. Nuclear DNA is stained green, RNA is stained red. Sympathetic nerve plexuses. Falk's method

Electron microscopy back An electron microscope is a device that allows obtaining images of objects with a maximum magnification of up to 10 6 times. This became possible due to the use of an electron beam instead of a light flux, the wavelength of which is many times shorter than the wavelength of visible light photons. An electron microscope consists of an electron gun (a device for obtaining an electron beam) and a system of electromagnetic lenses placed in a microscope column under vacuum conditions. The resolution of an electron microscope is 1000÷10000 times greater than the resolution of a light microscope and for the best modern instruments it can be less than 0.1 nm (m). There are two main types of electron microscopy: transmission (transmission) and scanning (raster). transmissionscanning table of contentsmore

Transmission (transmission) electron microscopy examples The principle of operation of a transmission electron microscope is that electrons passing through an object located near an objective lens interact with its atoms and deviate from the original direction of incidence of the beam (scatter). Then they enter a system of magnetic lenses, which form an image of the internal structure of the object on a fluorescent screen (and on photographic film). In this case, it is possible to achieve a resolution of the order of 0.1 nm, which corresponds to magnifications up to 1.5106 times. The resolution and information content of TEM images are largely determined by the characteristics of the object and the method of its preparation. To obtain a contrast image, ultrathin sections (no more than 0.01 μm) are used, treated with heavy metal compounds (impregnation with salts of lead, uranium, osmium, etc.), which selectively interact with the components of the microstructure (chemical contrasting). At the same time, the greater the scattering power of the area of ​​the object under study (areas of increased density, increased thickness, etc.), the darker its image will be.

Scanning (scanning) electron microscopy The principle of operation of a scanning electron microscope (SEM) is to scan the sample surface with a focused electron beam and analyze the particles reflected from it and X-rays resulting from the interaction of electrons with matter. In SEM, the electron beam (electron probe) is focused by the electromagnetic lenses of the condenser and objective. A special device - the deflector deflects the electron beam (primary electrons), which slides over the surface (raster). Secondary electrons (reflected from the surface) are perceived by the detector and focused on the SEM screen, creating its three-dimensional image. Three-dimensional image Modern SEM allows you to work in a wide range of magnifications from approximately x10 (which is equivalent to magnification of a strong hand lens) to x, which is approximately 500 times higher than the magnification limit of the best optical microscopes. The scanning surface must be sprayed with metal: platinum, gold, palladium, etc. back examples

Electron microscopy (examples) transmission scanning Mast cell back Erythrocytes in arteriole Erythrocyte, platelet, leukocyte contents more

Recommended literature back 1.Histology, cytology and embryology: Textbook. / Ed. Yu.A.Afanasiev, S.L.Kuznetsova, N.A.Yurina. – M.: Medicine, – 768 p. 2.Histology, embryology, cytology: Textbook. / Ed. E.G.Ulumbekova, Yu.A.Chelysheva. - M .: "GEOTAR-Media", - 408 p. 3. Junqueira L.K., Carneiro J. Histology: Atlas: Uch.pos.; per. from English, ed. V.L. Bykov. - M .: "GEOTAR-Media", - 576 p. 4. Ham A., Cormac D. Histology: in 5 volumes; per. from English. - M .: Mir, table of contents

1. Research methods in histology.

As any science, histology has its own arsenal of research methods:

I. The main method is microscopy.

A. Light microscopy - studies with a conventional light microscope.

B. Special microscopy methods:

Phase-contrast microscope (for the study of living unstained objects)

Dark-field microscope (for studying living unstained objects)

Luminescent microphone (for studying live unpainted objects)

Ultraviolet mic-p (increases the resolution of the mic)

Polarizing microphone (for research objects with an orderly arrangement of molecules - skeleton muscle, collagen fibers, etc.)

Interference microscopy (for determining the dry residue in

cells, determining the thickness of objects)

B. Electron microscopy:

Transmission (studying objects through the light)

Scanning (study of the surface of objects)

II. Special (non-microscopic) methods:

1. Cyto- or histochemistry - the essence is the use of strictly specific chemical reactions with a light end product in cells and tissues to determine the amount of various substances (proteins, enzymes, fats, carbohydrates, etc.). Can be applied at the level of a light or electron microscope.

2. Cytophotometry - the method is used in combination with 1 and makes it possible to quantify the proteins, enzymes, etc. identified by the cytohistochemical method.

3. Autoradiography - substances containing radioactive isotopes of chemical elements are introduced into the body. These substances are included in metabolic processes in cells. Localization, further movement of these substances in the organs are determined on histological preparations by radiation, which is captured by a photographic emulsion applied to the preparation.

4. X-ray diffraction analysis - allows you to determine the amount of chemical elements in cells, to study the molecular structure of biological micro-objects.

5. Morphometry - measuring the size of biol. structures at the cellular and subcellular levels.

6. Microurgy - performing very delicate operations with a micromanipulator under a microscope (nucleus transplantation, introduction of various substances into cells, measurement of biopotentials, etc.)

6. The method of culturing cells and tissues - in nutrient media or in diffusion chambers implanted in various tissues of the body.

7. Ultracentrifugation - fractionation of cells or subcellular structures by centrifugation in solutions of various densities.

8. Experimental method.

9. Method of tissue and organ transplantation.

2. In its research, embryology uses a number of methods: descriptive, experimental and comparative morphological.

The descriptive method consists in observing the changes that occur during the development of an individual. Their description was necessary as a prerequisite for the emergence of experimental and comparative morphological methods. The comparative morphological method consists in comparing the embryonic stages of different animals. With its help, similarities are established between the stages of development of various animal species, which significantly expands the significance of the descriptive method.

Experimental method - a branch of embryology that studies the process of embryogenesis under various experimental conditions in order to find ways and methods of purposeful influence on it. The use of experimental research methods makes it possible to establish the causes of a violation of normal individual development, to identify the conditions that determine the normal development of the organism, and also to actively intervene in this process. consists in studying the development of an individual under artificially altered conditions or under conditions of violation of the typical relationships between its parts. The latter is carried out by transplantation (transplantation) of the rudiments of organs into areas of the embryo that are unusual for them. Experimental research opens up wide opportunities for directed changes in shaping processes in the interests of man. In experimental embryology, various methods are used: such as dividing the embryo into parts and tracing the further development of these parts, transplanting parts of one embryo into another, changing the chemical. the composition of the environment in which development occurs, the method of marking (marking) parts of the embryo with harmless dyes, etc. The method of cultivating tissues and organ rudiments outside the body makes it possible to reveal not only the mechanisms of cytodifferentiation and the interaction of cells and tissues in the development process, but also to evaluate the direct effect of certain other agents, including drugs, on developing structures. With the help of experimental embryology, methods have been developed for storing (freezing) sperm and eggs, and embryo transfer. The latest achievement of experimental embryology was the development of the method of in vitro fertilization. The transplantation of embryos conceived in vitro into the uterus is the basis of infertility treatment.

According to the research methods used, embryology is divided into descriptive, comparative descriptive and experimental.

3. Contribution of domestic scientists to the development of histology

The beginning of the development of Russian histology should be considered the 30s of the 19th century, when histology was taught at the departments of anatomy and physiology. In the 1960s, histology separated into separate departments. The first department of histology was created at Moscow State University - the head of the department. A.I. Babukhin. Babukhin's school dealt with the issues of histogenesis and histophysiology of muscle and nervous tissue.

Almost in parallel, the department of histology was opened at the St. Petersburg Medical and Surgical Academy. This school includes K.E.Ber - an embryologist, NM Yakubovich - merits in the study of the central nervous system, MD Lavdovsky - the author of the first textbook on histology.

Kovalevsky AO - one of the founders of comparative embryology, experimental and evolutionary histology; established a unified plan for the development of multicellular organisms; substantiated the theory of germ layers as formations underlying the unity of development of all mammals.

The founder of the Department of Histology at the Kiev University - PI Peremezhko (1968). The Kyiv school achieved success in studying the development of germ layers, the formation and development of many organs.

The founder of the Kazan school - IA Arshtein - dealt with the problem of neurohistology.

Speaking about the contribution of domestic researchers to histology in the Soviet period, it should be noted:

1. Academician A.A. Zavarzin - proposed the theory of "parallel rows in tissue evolution" - the evolution of tissues in different types and classes of animals occurs in a similar way, in parallel rows, therefore, in different animals, tissues with related functions have a similar structure.

2. NG Khlopin - created the theory of "divergent evolution of tissues" - tissues develop in evolution and ontogenesis divergently, by divergence of signs. Therefore, in each of the 4 main groups of tissues, it is proposed to distinguish subgroups or types of tissues according to their origin, source of development.

The Department of Histology of the Belarusian State Medical University was established in 1934 under the leadership of Professor Nikolai Illarionovich Churbanov. The staff of the department was engaged in the study of the neuroendocrine apparatus of the digestive system, the development of hematological standards for various age groups of the population of the Republic of Bashkortostan, the influence of production factors on the mother and fetus in the mother:fetus system, the problem of muscle tissue regeneration.

4.Histology and embryology and their connection with biomedical disciplines.

Histology with cytology and embryology, like other biological sciences, solves the main problem - finding out the sources of development, patterns of histogenesis, reactivity and regeneration of tissues and, in connection with this, the possibility of targeted impact on them. Among the theoretical provisions of histology, an important place is occupied by the cell theory, the theory of germ layers, tissue evolution, histogenesis and regeneration.

Modern histology, cytology and embryology make a significant contribution to the development of theoretical and applied aspects of modern medicine and biology.

The fundamental theoretical problems 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, coordinated in time and space, etc.;

Elucidation of the mechanisms of tissue regulation (nervous, endocrine, immune), as well as age-related changes in tissues;

Study of patterns of reactivity and adaptive variability of cells and tissues under the influence of adverse 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 for gene therapy and transplantation of embryonic stem cells;

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

The course of histology with cytology and embryology is closely connected with the teaching of other biomedical sciences - biology, anatomy, physiology, biochemistry, pathological anatomy, as well as clinical disciplines. Thus, the disclosure of the basic patterns of the structural organization of cells is the basis for the presentation of genetics in the course of biology. On the other hand, the presentation of issues related to the evolution of living matter in the course of biology is a necessary prerequisite for studying the various levels of organization of living matter in the human body. The study of the structure of organs in the course of anatomy is based on the data of histological analysis. At present, when studies of cellular and tissue structures are carried out at the subcellular and molecular levels using biochemical, immunocytochemical methods, there is a particularly close connection between histology, cytology, and embryology with biochemistry and molecular biology. In teaching, research and clinical diagnostics, cyto- and histochemical data are widely used. Knowledge of the normal structure of cells, tissues and organs is a prerequisite for understanding the mechanisms of their changes in pathological conditions, therefore, histology with cytology and embryology is closely related to pathological anatomy and many clinical disciplines (internal medicine, obstetrics and gynecology, etc.). Thus, histology with cytology and embryology occupies an important place in the system of medical education. For modern medicine, with its focus on the prevention and early detection of pathological processes in the body, knowledge about the structural foundations and patterns of ensuring the stability and reliability of living systems (including tissues) is especially important, since the progressive development of civilization inevitably entails the emergence of new factors that are unfavorable affecting animals, including humans.

Objects of study subdivided into:

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

dead or fixed, which can be taken both from a living organism (biopsy) and from corpses.

In any case, after taking the pieces, they are subjected to the action of fixative solutions or freezing. Both scientific and educational purposes use fixed objects. Prepared in a certain way, preparations used for examination under a microscope are called histological preparations.

A histological preparation can be in the form of: (a thin colored section of an organ or tissue; a smear on glass; an imprint on glass from a fracture of an organ; a thin film preparation).

A histological preparation of any form must meet the following requirements: (preserve the intravital state of the structures; be thin and transparent enough to be studied under a microscope in transmitted light; be contrast, that is, the structures under study must be clearly defined under a microscope; preparations for light microscopy be used for re-learning.)

These requirements are achieved in the preparation of the drug.

Research methods:

Light microscopy-Microscopy - the main method of studying preparations - has been used in biology for over 300 years. ultraviolet microscopy- This is a kind of light microscopy. The ultraviolet microscope uses shorter ultraviolet rays with a wavelength of about 0.2 µm. Fluorescent (luminescent) microscopy- The phenomena of fluorescence are that the atoms and molecules of a number of substances, absorbing short-wavelength rays, go into an excited state. Phase contrast microscopy- This method is used to obtain contrast images of transparent and colorless objects, invisible with conventional microscopy methods. electron microscopy-The electron microscope uses a stream of electrons with shorter wavelengths than the light microscope.

The main stages of cytological and histological analysis are the choice of the object of study, its preparation for examination under a microscope, the use of microscopy methods, as well as the qualitative and quantitative analysis of images.

Most often, a section of a tissue or organ is used for study. Histological preparations can be studied without special processing. For example, a prepared blood smear, print, film, or section of an organ can be immediately viewed under a microscope. But due to the fact that the structures have a weak contrast, they are poorly detected in a conventional light microscope and the use of special microscopes (phase contrast, etc.) is required. Therefore, specially processed preparations are more often used: fixed, enclosed in a solid medium and colored.

The process of manufacturing a histological preparation for light and electron microscopy includes the following main steps:

1. taking the material and fixing it,

2. material compaction,

3. preparation of sections,

4. staining or contrasting sections.

For light microscopy, one more step is necessary - the conclusion of sections in a balm or other transparent media.

Fixation prevents decomposition processes, which helps to preserve the integrity of the organ structures. A small sample is either immersed in a fixative (alcohol, formalin, heavy metal salt solutions, osmic acid, special fixing mixtures) or subjected to heat treatment

The compaction of the material, necessary for the preparation of sections, is carried out by impregnating the previously dehydrated material with paraffin, celloidin, and organic resins. Faster compaction is achieved by using the method of freezing the pieces, for example, in liquid carbonic acid.

Slicing takes place on special devices - microtomes(for light microscopy) and ultramicrotomes(for electron microscopy).

Staining of sections (in light microscopy) or spraying them with metal salts (in electron microscopy) is used to increase the image contrast of individual structures when viewed under a microscope. Methods for staining histological structures are very diverse and are selected depending on the objectives of the study.

Histological dyes (according to their chemical nature) are divided into acidic, basic and neutral. Common dye hematoxylin, which stains cell nuclei purple, and an acidic dye - eosin staining the cytoplasm pink-yellow. The selective affinity of structures for certain dyes is due to their chemical composition and physical properties. Structures that stain well with acidic dyes are called oxyphilic, and those that stain with basic dyes are called basophilic. For example, the cytoplasm of cells most often stains oxyphilically, and the nuclei of cells stain basophilically.

Structures that accept both acidic and basic dyes are neutrophilic (heterophilic). Colored preparations are usually dehydrated in alcohols of increasing strength and cleared in xylene, benzene, toluene, or some oils. For long-term preservation, a dehydrated histological section is enclosed between a slide and cover slip in Canadian balsam or other substances. The finished histological preparation can be used for microscopic examination for many years.

four) . Cell as a structural and functional unit of tissue. Definition. General plan of the structure of eukaryotic cells. Biological cell membranes, their structure, chemical composition and main functions.

A cell is an elementary structural, functional and genetic unit in the composition of all plant and animal organisms. The structure of a eukaryotic cell:

The cells that form the tissues of animals and plants differ significantly in shape, size and internal structure. Cells of all types contain two main components that are closely related to each other - the cytoplasm and the nucleus. The nucleus is separated from the cytoplasm by a porous membrane and contains nuclear sap, chromatin, and the nucleolus. Semi-liquid cytoplasm fills the entire cell and is penetrated by numerous tubules. Outside, it is covered with a cytoplasmic membrane.

The cell body itself and its contents are separated from the external environment or from neighboring elements in multicellular organisms by a plasma membrane. Outside of the plasma membrane is a cell membrane or wall, which is especially well expressed in plants. The entire interior of the cell, with the exception of the nucleus, is called the cytoplasm. The cytoplasm of eukaryotic cells is not homogeneous in structure and composition and includes: hyaloplasm, membrane and non-membrane components. Membrane organelles are presented in two variants: single-membrane and double-membrane. The former include organelles of the vacuolar system - the endoplasmic reticulum, the Golgi apparatus, lysosomes, peroxisomes and other specialized vacuoles, as well as the plasma membrane. Two-membrane organelles include mitochondria and plastids, as well as the cell nucleus. Non-membrane organelles include ribosomes, the cell center of animal cells, as well as elements of the cytoskeleton (microtubules and microfilaments).
The term hyaloplasm, the main plasma or cytoplasmic matrix, denotes a very important part of the cell, its true internal environment. Hyaloplasm is a complex colloidal system that includes various biopolymers: proteins, nucleic acids, polysaccharides, etc. Enzymes involved in the synthesis of amino acids, nucleotides, fatty acids, and in the metabolism of sugars are localized in it. The most important role of hyaloplasm is that this environment unites all cellular structures and ensures their chemical interaction with each other. Most of the intracellular transport processes are carried out through the hyaloplasm: the transfer of amino acids, fatty acids, nucleotides, and sugars. In the hyaloplasm, there is a constant flow of ions to and from the plasma membrane, to the mitochondria, nucleus, and vacuoles. hyaloplasm is the deposition of spare products: glycogen, fat. In the cytosol, on the ribosomes located there, proteins are synthesized that are transported to different parts of the cell, as well as all proteins of the cell nucleus, most of the proteins of mitochondria and plastids, and the main proteins of peroxisomes. The structure of cell membranes.
A common feature of all cell membranes (plasmatic, intracellular and membrane organelles) is that they are thin (6-10 nm) layers of lipoprotein nature (lipids in complex with proteins), closed on themselves

There are three important principles of membrane structure:
The membranes are not homogeneous. The membranes surrounding intracellular organelles and the plasma membrane differ in composition. Many membrane components are in a state of continuous movement. The membrane resembles an ever-changing mosaic. The components of the membranes are extremely asymmetrical. Between the outer and inner layers of the membranes there is a difference in the relative quantity and qualitative composition of lipids. Proteins are asymmetrically arranged among lipids and have well-defined extra- and intracellular regions.

The most important functions of membranes are as follows:

Membranes control the composition of the intracellular environment.

Membranes provide and facilitate intercellular and intracellular information transfer.

Membranes provide tissue formation through intercellular contacts.

The chemical composition of the cell.
The cells of living organisms are similar not only in their structure, but also in chemical composition. The similarity in the structure and chemical composition of cells indicates the unity of their origin.

According to the composition of the substances entering the cell are divided into organic and inorganic.
1. Inorganic substances.
Water is of great importance in the life of the cell. Many elements in cells are contained in the form of ions. The most common are cations: K+, Na+, Ca2+ Mg2+, and anions: H2PO4-, Cl-, HCO3-.
Mineral salts (for example, calcium phosphate) can be part of the intercellular substance, shells of mollusks and provide the strength of these formations.
2. Organic substances.
Characteristic only for the living. Organic compounds are represented in the cell by simple small molecules (amino acids, mono- and oligosaccharides, fatty acids, nitrogenous bases), and macromolecules of biopolymers (proteins, lipids, polysaccharides, nucleic acids). Molecules of biopolymers consist of repeating low molecular weight compounds (monomers