Sinusitis

The structure of a microscope and what it is needed for. Microscope structure

PLANT CELL

A cell is a functional and structural unit of a living organism.

Microscope device

A microscope is used to magnify and examine small objects that are not visible with the naked eye. It is necessary when studying anatomical structure plants (Fig. 1). There are three parts to a microscope:

1.Optical (lens, eyepiece, diaphragm, condenser).

2. Mechanical (tube, tube holder, stage, revolver, macro- and micrometric screws, stand).

3. Lighting (mirror).

Fig.1. Microscope structure

Lens most important part microscope is a system of lenses enclosed in a metal frame. The microscope is equipped with several objectives with different magnifications (10X,40X,80X).

Mirror has two surfaces, one flat, the other concave. When working with a microscope, use a concave mirror.

Condenser consists of two or three lenses in a metal cylinder. Using a special screw, the condenser can be raised or lowered, thereby increasing or decreasing the illumination. Between the mirror and the condenser is located diaphragm, with which the lighting and image sharpness are adjusted.

Macrometric screw needed for rough aiming (focusing) of the image.

Micrometer screw necessary for moving the tube over short distances.

Subject table serves to place a micropreparation on it. There are two clamps on the table for securing the drug.

Rules for working with a microscope

1. The microscope should be taken by the arched part of the tube holder.

2. The microscope is placed on the table so that the arc-shaped tube holder is facing towards you, the mirror and the object stage are facing away from you.

3. The microscope installed at the beginning of work cannot be moved from place to place, as the lighting conditions are disrupted.

4.The notebook and all the items necessary for work are located to the right of the microscope.

5. The microscope is illuminated at low magnification (8X) with a mirror with the concave side. Looking at the mirror from the side, we direct it towards the light source. Then, with your left eye (the right eye is always open), we look into the eyepiece and achieve maximum illumination.

6. Place the finished microslide on the object table and secure it with clamps.

7.Looking at the 8X lens from the side, use the macrometric screw to lower the lens to a distance of less than 1 cm from the specimen. Then, looking into the eyepiece, use the same macroscrew to turn it toward you until you get a clear image (focal length). Focal length - This is the distance from the object in question to the objective lens. At low magnification it is 1 cm.

8.To examine the drug at high magnification (40X), you need to change the lens using a revolver, turn it until it clicks. The focal length is set in the same way as at low magnification. The focal length at high magnification is 1 mm.

9.After sketching the drug at high magnification, turn the revolver and set the magnification to low. Then remove the drug. Lower the macroscrew down - this is not the working condition of the microscope.

10. Put the microscope in a cabinet that protects it from mechanical damage and dust (Fig. 2).

Fig.2. Working with a microscope

→

The design of a microscope directly depends on its purpose. As you probably already guessed, there are different microscopes, and an optical microscope will differ significantly from an electron or X-ray microscope. This article will examine in detail the structure optical light microscope, which is on at the moment is the most popular choice amateurs and professionals, and with which you can solve many research problems.

Optical microscopes also have their own classification and can differ in their structure. However, there is a basic set of parts that go into any optical microscope. Let's look at each of these details.

A microscope can be divided into optical and mechanical parts. The optics of a microscope include objectives, eyepieces, and a lighting system. A tripod, tube, stage, mounts for the condenser and light filters, mechanisms for adjusting the stage and tube holder make up the mechanical part of the microscope.

Let's start, perhaps, with optical part .

Eyepiece. That part optical system, which is directly related to the eyes of the observer. In the simplest case, the lens consists of a single lens. Sometimes, for greater convenience, or, as they say, “ergonomics,” the lens can be equipped, for example, with an “eyecup” made of rubber or soft plastic. Stereoscopic (binocular) microscopes have two eyepieces.
Lens. Perhaps the most important part of the microscope, providing the main magnification. The main parameter is aperture; what it is is described in detail in the section “Basic parameters of microscopes”. Objectives are divided into “dry” and “immersion”, achromatic and apochromatic, and even in cheap simple microscopes they represent a rather complex lens system. Some microscopes have standardized lens mounting elements, which allows the device to be configured in accordance with the tasks and budget of the consumer.
Illuminator. Very often an ordinary mirror is used, which allows daylight to be directed onto the sample under study. Currently, special halogen lamps are often used, which have a spectrum close to natural white light and do not cause gross color distortions.
Diaphragm. Most microscopes use so-called “iris” diaphragms, so named because they contain petals similar to the petals of an iris flower. By moving or spreading the petals, you can smoothly adjust the strength of the light flux entering the sample being studied.
Collector. Using a collector located near the light source, a luminous flux is created that fills the condenser aperture.
Condenser. This element, which is a converging lens, forms a light cone directed at the object. The intensity of illumination is regulated by the diaphragm. Most often, microscopes use a standard two-lens Abbe condenser.

Worth noting that an optical microscope can use one of two main methods of illumination: transmitted light illumination and reflected light illumination. In the first case, the light flux passes through the object, resulting in the formation of an image. In the second, light is reflected from the surface of the object.

As for the optical system as a whole, depending on its structure, it is customary to distinguish direct microscopes (lenses, attachment, eyepieces are located above the object), inverted microscopes (the entire optical system is located under the object), stereoscopic microscopes (binocular microscopes, essentially consisting of two microscopes located at an angle to each other and forming a three-dimensional image).

Now let's move on to mechanical part of the microscope .

Tube. The tube is a tube that contains the eyepiece. The tube must be strong enough and should not deform, which will worsen the optical properties, therefore only in the cheapest models the tube is made of plastic; more often aluminum, stainless steel or special alloys are used. To eliminate glare, the inside of the tube is usually coated with black light-absorbing paint.
Base. It is usually quite massive, made of metal casting, to ensure the stability of the microscope during operation. On this base, a tube holder, tube, condenser holder, focusing knobs, a revolving device and an attachment with eyepieces are attached.
Turret for quickly changing lenses. As a rule, cheap models with only one lens do not have this element. The presence of a turret allows you to quickly adjust the magnification by changing lenses by simply turning it.
Subject table, on which the test samples are placed. These are either thin sections on glass slides for “transmitted light” microscopes, or volumetric objects for “reflected light” microscopes.
Fastenings, with which the slides are fixed on the stage.
Coarse focus adjustment screw. Allows you to achieve the clearest image by changing the distance from the lens to the sample being examined.
Fine focus screw. The same thing, only with a smaller pitch and less “lead” of the thread for the most precise adjustment.

Microscope device

Parameter name	Meaning
Article topic:	Microscope device
Rubric (thematic category)	Story

From the history of the microscope

CoolReferat.com

In Vasily Shukshin's story "Microscope", the village carpenter Andrei Erin bought the dream of his whole life - a microscope - with the salary "withheld" from his wife and set as his goal to find a way to eliminate all microbes on earth, since he sincerely believed that, without them, a person could would live more than one hundred and fifty years. And only an unfortunate misunderstanding prevented him from this noble cause. For people of many professions, a microscope is an extremely important piece of equipment, without which it is simply impossible to carry out many studies and technological operations. Well, in “home” conditions this optical instrument allows everyone to expand the boundaries of their capabilities by looking into the “microcosm” and exploring its inhabitants.

The first microscope was not designed by a professional scientist, but by an “amateur”, a textile merchant, Anthony Van Leeuwenhoek, who lived in Holland in the 17th century. It was this inquisitive self-taught man who was the first to look through a device he made himself at a drop of water and saw thousands of tiny creatures, which he named Latin word animalculus (ʼʼsmall animalsʼʼ). During his life, Leeuwenhoek managed to describe more than two hundred species of “little animals”, and by studying thin sections of meat, fruits and vegetables, he discovered cellular structure living tissue. For services to science, Leeuwenhoek was elected a full member of the Royal Society in 1680, and a little later became an academician of the French Academy of Sciences.

Leeuwenhoek's microscopes, of which he personally made more than three hundred during his life, were a small, pea-sized, spherical lens inserted into a frame. Microscopes had a stage, the position of which relative to the lens could be adjusted using a screw, but these optical instruments did not have a stand or tripod - they had to be held in the hands. From the point of view of today's optics, the device, which is commonly called the Leeuwenhoek microscope, is not a microscope, but a very strong magnifying glass, since its optical part consists of only one lens.

Over time, the design of the microscope has evolved significantly, new types of microscopes have appeared, and research methods have been improved. At the same time, working with an amateur microscope to this day promises many interesting discoveries for both adults and children.

A microscope is an optical device designed to study magnified images of micro-objects that are invisible to the naked eye.

The main parts of a light microscope (Fig. 1) are the lens and the eyepiece, enclosed in a cylindrical body - a tube. Most models designed for biological research, are equipped with three lenses with different focal lengths and a rotating mechanism designed for quickly changing them - a turret, often called a turret. The tube is located on the top of a massive tripod, which includes a tube holder. Just below the lens (or a turret with several lenses) there is a stage on which slides with the samples under study are mounted. Sharpness is adjusted using the coarse and fine adjustment screw, which allows you to change the position of the stage relative to the lens.

In order for the sample under study to have sufficient brightness for comfortable observation, microscopes are equipped with two more optical units (Fig. 2) - an illuminator and a condenser. The illuminator creates a stream of light that illuminates the test specimen. In classical light microscopes, the design of the illuminator (built-in or external) involves a low-voltage lamp with a thick filament, a collecting lens and a diaphragm that changes the diameter of the light spot on the sample. The condenser, which is a collecting lens, is designed to focus the illuminator beams on the sample. The condenser also has an iris diaphragm (field and aperture), with which the light intensity is adjusted.

When working with objects that transmit light (liquids, thin sections of plants, etc.), they are illuminated with transmitted light - the illuminator and condenser are located under the object stage. Opaque samples need to be illuminated from the front. To do this, the illuminator is placed above the object stage, and its rays are directed to the object through the lens using a translucent mirror.

The illuminator must be passive, active (lamp) or consist of both elements. The simplest microscopes do not have lamps to illuminate samples. Under the table they have a two-way mirror, one side of which is flat and the other is concave. In daylight, if the microscope is placed near a window, you can get pretty good illumination using a concave mirror. If the microscope is in a dark room, they are used for illumination. flat mirror and external illuminator.

The magnification of a microscope is equal to the product of the magnification of the objective and the eyepiece. With an eyepiece magnification of 10 and an objective magnification of 40, the total magnification factor is 400. Typically, a research microscope kit includes objectives with a magnification of 4 to 100. A typical set of microscope lenses for amateur and educational research(x 4, x10 and x 40), provides an increase from 40 to 400.

Resolution – different most important characteristic microscope, which determines its quality and clarity of the image it forms. The higher the resolution, the more fine details can be seen at high magnification. In connection with resolution, they talk about “useful” and “useless” magnification. “Useful” is usually called the maximum magnification at which maximum image detail is provided. Further magnification ("useless") is not supported by the resolution of the microscope and does not reveal new details, but can negatively affect the clarity and contrast of the image. Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, limit useful increase The magnification of a light microscope is limited not by the overall magnification factor of the objective and eyepiece - it can be made as large as desired - but by the quality of the optical components of the microscope, that is, the resolution.

The microscope includes three main functional parts:

1. Lighting part Designed to create a light flux that allows you to illuminate an object in such a way that subsequent parts of the microscope perform their functions with extreme precision. The illuminating part of a transmitted light microscope is located behind the object under the lens in direct microscopes and in front of the object above the lens in inverted microscopes. The lighting part includes a light source (lamp and electrical power supply) and an optical-mechanical system (collector, condenser, field and aperture adjustable/iris diaphragms).

2. Reproducing part Designed to reproduce an object in the image plane with the image quality and magnification required for research (ᴛ.ᴇ. to construct such an image, ĸᴏᴛᴏᴩᴏᴇ would reproduce the object as accurately as possible and in all details with a resolution, magnification corresponding to the optics of the microscope, contrast and color rendition). The reproducing part provides the first stage of magnification and is located after the object to the microscope image plane. The reproducing part includes a lens and an intermediate optical system. Modern microscopes latest generation are based on optical lens systems corrected for infinity. This additionally requires the use of so-called tube systems, which “collect” parallel beams of light emerging from the lens in the microscope image plane.

3. Visualizing part Designed to obtain a real image of an object on the retina, photographic film or plate, on the screen of a television or computer monitor with additional magnification (second stage of magnification).

The visualizing part is located between the image plane of the lens and the eyes of the observer (camera, photo camera). The imaging part includes a monocular, binocular or trinocular imaging head with an observation system (eyepieces that work like a magnifying glass). At the same time, this part includes additional magnification systems (wholesaler/magnification change systems); projection attachments, incl. discussion for two or more observers; drawing apparatus; image analysis and documentation systems with corresponding matching elements (photo channel).

The device of a microscope - concept and types. Classification and features of the category "Microscope Device" 2017, 2018.

The study of the morphological characteristics of microbes - their shape, structure and size of cells, ability to move, etc. - is carried out using an optical device - a microscope (from the Greek “micros” - small, “skopeo” - I look). Of the biological microscopes produced, the best are MBI-1, MBI-2, MBI-3, MBR-1 and some others.

The main parts of a microscope are: the optical system (lens and eyepiece), the illuminating optical system (condenser and mirror) and the mechanical part. The optical system creates a magnified image of the object. Mechanical part ensures the movement of the optical system and the observed object (subject). Main parts mechanical system microscope (Fig. 60) are: a tripod, a stage, a tube holder with a revolver and screws for moving the tube - macrometric and micrometric.

A macrometric screw (crackle, or gear) is used for rough aiming of the microscope. The micrometer screw is a fine feed mechanism and serves for the final, precise focusing of the microscope on the specimen. Full turn The microscrew moves the microscope tube by 0.1 mm. The micrometer screw is one of the most fragile parts of the microscope and must be handled with extreme care. The sharpest and clearest image is obtained by moving the tube using macro- and micrometer screws with appropriate lighting settings. The microscope tube is fixed in the upper part of the tripod in a tube holder. The object stage is also fixed at the top of the tripod. U modern microscopes the stage is almost always made movable. It is driven by two screws located on both sides of the table. With the help of these screws, the preparation, together with the table, moves into different directions, which greatly facilitates the examination of the drug at its various points. The drug is secured to the table with two terminals (clamps).

In addition to movable stages, some microscopes are equipped with cross-shaped stages. In this case, the drugs are moved in two mutually perpendicular directions. Two scales on the table allow you to mark areas of interest to the researcher so that they can be easily found during repeated microscopy.

At the bottom of the tube holder there is a revolver with holes equipped with threads. Lenses are screwed into these holes. Objectives make up the most important and expensive part of a microscope. This complex system biconvex lenses enclosed in a metal frame. Lenses magnify the subject being viewed, producing a truly magnified reverse image.

All lenses are divided into achromats and apochromats. Achromats are more common due to their simplicity and low cost. They have six lenses made from optical glass. The image obtained with achromats is sharpest in the center. The edges of the field due to chromatic aberration are often colored blue, yellow, green, red and other colors. Apochromats consist of more lenses (up to 10). For their manufacture, glass of various types is used. chemical composition: boric, phosphoric, fluorite, alum. In apochromats, chromatic aberration is largely eliminated.

Typically, microscopes are equipped with three objectives, which indicate the magnification they provide: 8X (low magnification), 40X (medium magnification) and 90X (high magnification) objectives. 8X and 40X lenses are dry systems, since when working with them there is a layer of air between the drug and the lens. Rays of light, passing through media of different densities (refractive index of air n = 1, glass n = 1.52) and getting from a denser medium (glass) to a less dense one (air), are strongly deflected and do not completely enter the microscope lens. Therefore, dry lenses can only be used at relatively low magnifications (up to 500-600 times).

The higher the magnification, the smaller the diameter of the lenses. Therefore, at high magnifications, too little of the rays enter the objective lens and the image is not clear enough. To avoid this, they resort to immersion (immersion) of the lens in a medium having a refractive index close to the refractive index of glass. Such an immersion, or submersible, objective in biological microscopes is the 90X objective. When working, a drop of immersion (most often cedar) oil, the refractive index of which is 1.51, is placed between this lens and a glass slide. The lens is immersed directly in oil, light rays pass through a homogeneous system without refraction or scattering, which helps to obtain a clear image of the object in question.

IN top part An eyepiece is inserted into the microscope tube. The eyepiece consists of two converging lenses: one facing the objective and one facing the eye. Between them in the eyepiece there is a diaphragm that blocks side rays and transmits rays parallel to the optical axis. This provides a higher contrast intermediate image. The eye lens of the eyepiece magnifies the image received from the objective. Eyepieces are manufactured with their own magnification of 7X, 10X, 15X times. The total magnification of a microscope is equal to the magnification of the objective multiplied by the magnification of the eyepiece. By combining eyepieces with objectives, various magnifications can be obtained - from 56 to 1350 times.

The condenser is a biconvex lens that collects light reflected from the mirror into a beam and directs it into the plane of the preparation, which provides the best illumination of the object. By raising and lowering the condenser, you can adjust the degree of illumination of the preparation. At the bottom of the condenser there is an iris diaphragm, through which you can also change the brightness of the lighting, narrowing it or, conversely, fully opening it.

The mirror, which has two reflective surfaces - flat and concave, is mounted on a swinging lever, with which it can be installed in any plane. The concave side of the mirror is rarely used - when working with weak lenses. The mirror reflects light rays and directs them into the lens through the condenser iris, the condenser and the object being viewed. At the bottom of the condenser frame there is a folding frame, which is used for installing light filters.

A microscope is a complex optical device; it requires careful and careful handling and appropriate operating skills. Proper care of the device and careful adherence to the instructions for use guarantee its impeccable and long-term service. Microscope image quality is highly dependent on illumination, so adjusting the illumination is an important preparatory step.

Work with a microscope can be carried out both under natural and artificial lighting. For responsible work they use artificial lighting, using the OI-19 illuminator. In natural light, you need to use diffused side light rather than direct sunlight.

Modern microscopes MBI-2, MBI-3 are equipped with binocular attachments of the AU-12 type, which have their own magnification of 1.5x, and a direct replaceable tube (Fig. 61). When using a binocular attachment, microscopy is facilitated, since observation is carried out with both eyes and vision does not become tired.

1-topic. Light microscopes, structure and rules

working with them

Topic content.

One of the main methods for studying small biological objects (viruses, microorganisms, protozoa, cells, multicellular organisms) is microscopy - studying them using optical magnifying devices (micros - small, scopio - observe). There are different types microscopes (light, electron, luminescent, phase-contrast, fluorescent, polarizing, etc.). More often used light microscopes, which are necessary not only for biological but also medical research, for example for laboratory diagnostics diseases. Therefore, every student is required to know the structure of light microscopes and be able to work with them.

A light microscope consists of the following parts: a) optical, b) mechanical, c) lighting. (Fig. 1; table 1.).

To the mechanical part include: tripod, stage, revolver tube, macro and micrometric screws. The tripod consists of a base, a tube holder and a tube. The object table has a round hole in the center through which a beam of light passes, two clamps for fixing the specimen, and specimen guides-screws for moving the upper part of the table along a horizontal plane. Below the object stage there are macrometric and micrometric screws. The macrometric screw is larger and serves for approximate focusing, and the micrometric screw for more precise focusing. In most microscopes, the microscrew looks like a massive disk and is located on the base.

Lighting part consists of a mirror, condenser and diaphragm.

Mirror movably mounted on a tripod below the object stage; it can be rotated in any direction. The mirror has a concave and flat surface. In low light conditions, a concave surface is used. The condenser is also located under the stage and consists of a lens system. There is a special screw to move the condenser up or down,

Fig-1. Microscope MBR-I.

1-base (tripod); 2-tube holder; 3-tube; 4-piece table; 5-hole of the object table; 6-screws that move the table; 7-eyepiece; 8-lens;

9-macrometric screw; 10 micrometer screw; 11-condenser; 12-screw condenser; 13-diaphragm; 14-mirror; 15-revolver.

Table-1

Microscope structure

Subject table

I. Mechanical part Tube

Revolver

Macro and micrometric screws

Light II.Lighting Mirror

microscope part Condenser

Iris diaphragm

Low power lens (8 x)

III.Optical part High magnification lens (40 x)

Immersion lens (90 x)

with which the degree of illumination is adjusted. When lowering the condenser, the illumination decreases, when raising it increases.

Iris diaphragm screwed into bottom part condenser, consists of small plates. Using a special terminal, you can adjust the diameter of the hole and the illumination of the object being studied.

To the optical part microscope includes eyepieces and objectives. Eyepieces consist of a system of lenses. The magnification power of the eyepiece is indicated on the top surface (7, 10, 15, 20)

Lenses screwed into special sockets of the revolver. The rotating revolver has 4 lens sockets. Objectives also have different magnification ratios (8 x, 40 x, 60 x, 90 x) by the magnifying power one can judge the “power of the microscope”. When calculating the power of the microscope, you should multiply the magnification of the eyepiece by the magnification of the objective (for example, 10 x 8 = 56.10 x 40 = 400, 10 x 90 = 900, etc.)

The concept of “resolution” is often used to characterize optical devices. The resolution of a microscope is the smallest distance between two point objects at which they can be distinguished. The human eye (a kind of optical device) can distinguish two points 25 cm away from it, with a distance between them of at least 0.073 mm. The resolution of the light microscope is 0.2 µm, the electron microscope is 5A 0 (1 Angstrom =
µm)

Rules for working with a microscope.

1. The microscope is installed with the tripod facing you, at a distance of 5 cm from the edge of the table.

2.The eyepiece, lens, mirror and other parts of the microscope are wiped with a soft cloth.

3. Using a revolver, a low-magnification lens is installed in the center of the object stage, a slight click is heard and the revolver is fixed.

It is necessary to remember that the study of any object begins with low magnification .

4. Using a macrometric screw, the low-magnification lens is raised to a height of 0.5 cm from the object stage.

5.Looking at the eyepiece with your left eye and rotating the mirror in different directions, bright and uniform illumination of the field of view is established. To do this, widen the hole in the diagram and raise the condenser. When there is sufficient illumination, a flat mirror surface is used.

6. The drug under study is installed in the center of the stage and secured with clamps. Using a macroscrew, the small objective is slowly lowered to a distance of approximately 2 mm from the specimen. Then, looking into the eyepiece with the left eye, slowly rotating the macrometric screw, the small lens is raised until the image of the object being studied appears in the field of view. The focal length of the low magnification lens is 0.5cm. When a clear image of the drug appears in the desired area, this part is installed in the center of the field of view. Then a high magnification lens is installed. Under visual control, the lens is lowered almost to contact with the preparation. After this, looking through the eyepiece, it slowly rises until a clear image appears. The focal length when working with a high magnification lens is 1mm. If there is no image, repeat the work from the beginning. For fine focusing, a micrometer screw is used, rotating it half a turn to the right and left.

Explain the concept of microscope power, microscope resolution.

7. A lens with a magnification of 90 x is called immersion (from the Latin Immersio - to immerse). This lens is used when studying the smallest objects. When using this lens, a drop of immersion (cedar) oil is placed on the object being studied. Then, looking from the side, the tube is lowered until the objective lens is immersed in the oil. After this, looking through the eyepiece, using only the microscrew, the lens is carefully lowered or raised until a clear image is obtained.

8.After completion of work, the microscope should be moved to the non-working position. To do this, by rotating the revolver, the lenses are moved to the neutral position.

Purpose of the lesson.

Familiarization with the structure of a microscope, mastering the rules of working with it, techniques for preparing temporary preparations, studying temporary and permanent microscopic preparations.

Assignment for self-study.

I.Study the material on the topic and answer the following questions:

1.Meaning microscopic studies in biology and medicine.

2.What types of microscopes are there?

3.List the main parts of a microscope.

4.Learn the rules of working with a microscope.

5. Using additional literature, tell us about the operating principles of different microscopes.

II Solve situational problems and answer test questions.

Educational equipment.

Microscopes, Petri dishes, slides and cover glasses, pipettes, glasses with water, tweezers, scissors, cotton wool, immersion oil, permanent micropreparations, tables depicting the structure of the microscope, various cells and fabrics

Lesson plan.

Students study the structure of a microscope and the rules of working with them, master the technique of preparing temporary preparations.

preparation. A piece of hair approximately 1-1.5 cm long is placed on slide and drop one drop of water from a pipette and cover with a coverslip. The drug is studied first at low, then at high magnification of the microscope, and the image is sketched in an album.

2- drug. A small bundle of cotton wool fibers is taken from a Petri dish with tweezers, placed on a glass slide, loosened, a drop of water is added, and covered with a coverslip. The drug is studied first at low, then at high magnification, the image is sketched in an album, cotton wool fibers and air bubbles are designated. In the final part of the lesson, the teacher checks the album, mastery of the material using tests and situational tasks, evaluates progress and explains the task for the next lesson.

Situational tasks.

1. A student, working at low magnification, was unable to find an image of an object. List the mistakes made by the student.

2.When switching to high magnification, the student was unable to find an image of the object. What mistakes did the student make?

3. During microscopy, the student broke the specimen. Give reasons.

Test tasks.

1.Main parts of the microscope:

A. Mechanical. B. Optical. C. Lighting. D. Lens and aperture.

E. All parts of the microscope are basic.

2.Immersion lens is:

A. Low magnification lens. B. High magnification lens.

C. All lenses are considered immersion lenses.

D. Lens with a magnification of 90 x when working with immersion oil. E. All answers are incorrect.

3.The operating principle of an electron microscope is based on:

A. On the use of light radiation.

B. Using the flow of electrons.

C. On the use of electromagnetic lenses.

4. Disadvantages of permanent medications:

A. Absent.

B. When fixing the object being studied, minor changes occur.

C. Inability to study the drug at high magnification.

D. Answers B and C are correct; E. All answers are incorrect.

5.Which microscope can be used to study biological objects? alive?

A. Fluorescent microscope. B. Phase contrast microscope.

WITH. Electron microscope. D Answers A and B are correct. All answers are correct.

6. How is the magnification of the object being studied determined?

A. According to the numbers on the lens; B. According to the numbers on the eyepiece;

C. According to the numbers on the tube; D. Multiplying the magnification of the eyepiece by the magnification of the objective; E. Multiplying the lens number by the tube number.

7. Revolver Meaning:

A. Serves to move the tube; B. Used to change lenses.

C. Serves to establish the right lens under the tube.

D. Answers A and C are correct; E. Answers B and C are correct.

8.What changes in the position of the diaphragm and condenser can be used to achieve uniform and good illumination of the object?

A. By lowering the condenser, narrowing the opening of the diaphragm.

B. Raising the condenser, narrowing the opening of the diaphragm.

C. Raising the condenser, widening the hole.

D. Answers A and B are correct. E. All answers are incorrect.

9. Indicate the reasons for the lack of an image of an object when switching from low to high magnification.

A. The high magnification lens is not fixed.

B. The object being studied is not centered.

S.No focal length. D. All answers complement each other.

E. All answers are incorrect.

10.Which lens does the study of an object begin with?

A. From an immersion lens. B. From a high magnification lens.

With a special lens. D.You can start with any lens

E. From a low magnification lens.

2-topic. Cell structure. Cytoplasm.

The cell is the elementary structural, functional and genetic unit of living things. Knowledge about the structure and function of the cell serves as the foundation for mastering morphological and biomedical disciplines. Doctors use data from cytological studies in their practice. The structure of cells is divided into prokaryotic and eukaryotic.

Prokaryotic cells include bacteria and blue-green algae. They lack a nucleus and instead contain one ring-shaped chromosome.

Eukaryotic cells are divided into protozoa (unicellular) and multicellular cells (Table 2). On practical exercises we are studying eukaryotic cells.

Cell shape depends on the functions performed. For example, contractile function muscle cells ensured by their elongated shape, long shoots nerve cells determine the conductivity of nerve impulses.

Cell sizes vary widely (from 2-3 micrometers to 100 or more). The eggs of some organisms can reach up to 10 cm. Human lymphocytes and red blood cells are small cells. Main structural components eukryotic cells are: cell membrane, cytoplasm and nucleus . The cell membrane surrounds the cytoplasm and separates it from environment. The cell membrane includes the plasma membrane, supra-membrane organic molecules and sub-membrane cytoskeletal organelles. U plant cells(Fig. 2.) The thick layer above the membrane consists mainly of cellulose. In animal cells (Fig. 3.), a supramembrane glycocalyx is formed, consisting of complex glycoproteins, the thickness of which does not exceed 10-20 nm.

The basis of the plasmalemma makes up a bimolecular lipid layer; protein molecules are differently immersed in this lipid layer.

Functions of the plasmalemma: protection of the cytoplasm from factors external environment, ensuring the transport of substances. Plasma membrane receptors provide the cell's response to the action of hormones and other biologically active substances.

Cytoplasm consists of hyaloplasm, organelles, and inclusions . Hyaloplasm is a matrix of cytoplasm, a complex, colorless colloidal system. It contains proteins, RNA, lipids, and polysaccharides. The hyaloplasm ensures the transport of substances and their interaction, as well as the buffering and osmotic properties of the cell.

Table-2

E UCARYOTES