Lifeless and empty: Planets without a core. Livepatch - updating the Ubuntu kernel without rebooting Cells without a kernel are called

Biology studies all life on planet Earth, starting with the global ecosystem of the Earth - the biosphere - and ending with the smallest living particles - cells. The branch of biology that deals with cells is called "cytology". She studies all living cells, which are nuclear and non-nuclear.

The meaning of the nucleus for a cell

As the name suggests, anucleate cells do not have a nucleus. They are characteristic of prokaryotes, which themselves are such cells. Proponents of the theory of evolution believe that eukaryotic cells evolved from prokaryotic cells. The main difference between eukaryotes in the development of life was the cell nucleus. The fact is that the nuclei contain all the hereditary information - DNA. Therefore, for eukaryotic cells, the absence of a nucleus is usually a deviation from the norm. However, there are exceptions.

Prokaryotic organisms

Nuclear-free cells are prokaryotic organisms. Prokaryotes are the oldest creatures consisting of a single cell or colony of cells; these include bacteria and archaea. Their cells are called prenuclear.

The main feature of prokaryotic cell biology is, as already mentioned, the absence of a nucleus. For this reason, their hereditary information is stored in an original way - instead of eukaryotic chromosomes, prokaryotic DNA is “packed” into a nucleoid - a circular region in the cytoplasm. Along with the absence of a formed nucleus, there are no membrane organelles - mitochondria, Golgi apparatus, plastids, endoplasmic reticulum. Instead, the necessary functions are performed by mesosomes. Prokaryotic ribosomes are much smaller in size and fewer in number than eukaryotic ones.

Nuclear-free plant cells

Plants have tissues consisting of only anucleate cells. For example, bast or phloem. It is located under the integumentary tissue and is a system of different tissues: main, supporting and conductive. The main element of bast, related to conductive tissue, is sieve tubes. They consist of segments - elongated anucleate cells with thin cell walls, the main components of which are cellulose and pectin substances. They lose the nucleus upon maturation - it dies, and the cytoplasm turns into a thin layer located near the cell wall. The life of these anucleate cells is associated with satellite cells that have a nucleus; they are closely related to each other and actually form one whole. The segments and satellites develop in a common meristematic cell.

Sieve tube cells are living, but this is the only exception; all other cells without a nucleus in plants are dead. In eukaryotic organisms (which include plants), nuclear-free cells can live for a very short time. The cells of the sieve tubes are short-lived; after death, they form the surface layer of the plant - the integumentary tissue (for example, the bark of a tree).

Nuclear-free human and animal cells

In the human body and mammals there are also cells without a nucleus - red blood cells and platelets. Let's take a closer look at them.

Red blood cells

Otherwise they are called red blood cells. At the formation stage, young red blood cells contain a nucleus, but adult cells do not.

Red blood cells provide oxygen saturation of organs and tissues. With the help of the pigment hemoglobin contained in red blood cells, the cells bind oxygen molecules and carry them from the lungs to the brain and other vital organs. They also participate in the removal of the product of gas exchange - carbon dioxide CO 2 - from the body, transporting it.

Human red blood cells are only 7-10 microns in size and have the shape of a biconcave disc. Due to their small size and elasticity, red blood cells easily pass through capillaries, which are much smaller in size. As a result of the absence of the nucleus and other cellular organelles, the amount of hemoglobin in the cell is increased; hemoglobin fills its entire internal volume.

Red blood cell production takes place in the bone marrow of the ribs, skull and spine. In children, the bone marrow of the leg and arm bones is also involved. More than 2 million red blood cells are formed every minute and live for about three months. An interesting fact is that red blood cells make up approximately ¼ of all human cells.

Platelets

Previously, they were also called blood platelets. These are small, anucleate, flat-shaped blood cells, the size of which does not exceed 2-4 microns. They are fragments of cytoplasm that have separated from bone marrow cells - megakaryocytes.

The function of platelets is to form a blood clot, which “plugs” damaged areas in the vessels, and to ensure normal blood clotting. Blood platelets can also secrete compounds that promote cell growth (called growth factors), so they are important for the healing of damaged tissue and promote tissue regeneration. When platelets are activated, that is, they transition to a new state, they take the shape of a sphere with projections (pseudopodia), with the help of which they adhere to each other or the vascular wall, thereby closing its damage.

Deviation of the platelet count from the norm can lead to various diseases. Thus, a decrease in the number of blood platelets increases the risk of bleeding, and their increase leads to vascular thrombosis, that is, the appearance of blood clots, which in turn can cause heart attacks and strokes, pulmonary embolism and blockage of blood vessels in other organs.

Platelets are produced in the bone marrow and spleen. After formation, 1/3 of them are destroyed, and the remaining ones circulate in the bloodstream for a little longer than a week.

Corneocytes

Some human skin cells also do not contain nuclei. The two upper layers of the epidermis are composed of anucleate cells - the horny and shiny (cycloid). Both consist of the same cells - corneocytes, which are former cells of the lower layers of the epidermis - keratinocytes. These cells, formed at the border of the outer and middle layers of the skin (dermis and epidermis), rise as they “grow up” higher and higher, into the spinous and then into the granular layers of the epidermis. The keratin protein it produces accumulates in the keranocyte - an important component that is responsible for the strength and elasticity of our skin. As a result, the cell loses its nucleus and almost all organelles, so the majority of it is made up of the protein keratin.

The resulting corneocytes have a flat shape. Adhering tightly to each other, they form the stratum corneum of the skin, which serves as a barrier to microorganisms and many substances - its scales perform a protective function. The transitional layer from granular to horny is the shiny layer, which also consists of keratinocytes that have lost their nuclei and organelles. Essentially, corneocytes are dead cells, since no active processes occur in them.

Nuclear-free cells in transplantology

To clone cells of the desired tissues in transplantology, artificially created nuclear-free cells are used. Since the nucleus stores genetic information in eukaryotic organisms, by manipulating it it is possible to influence the properties of the cell. No matter how fantastic it may sound, you can replace the nucleus and in this way get a completely different cell. To do this, the nuclei are removed or destroyed in various ways - surgically, using ultraviolet radiation or centrifugation in combination with the influence of cytochalasins. A new nucleus is transplanted into the resulting nuclear-free cell.

Until now, scientists have not come to a common opinion on the ethics of cloning, which is why it is still banned.

Thus, in fact, living anucleate cells are almost never found in higher (eukaryotic) organisms. The exceptions are human blood cells - erythrocytes and platelets, as well as phloem cells in plants. In other cases, anucleated cells cannot be called living, such as cells in the upper layers of the epidermis or cells obtained artificially for tissue cloning in transplantology.

Erythrocyte - what is it? What is its structure? What is hemoglobin?

Blood group and Rh factor antigens

Where does the red blood cell come from in the blood?

Reticulocyte, precursor of red blood cell

In addition to red blood cells, there are reticulocytes in the blood. A reticulocyte is a slightly “immature” red blood cell. Normally, in a healthy person their number does not exceed one per 1000 red blood cells. However, in the case of acute and large blood loss, both red blood cells and reticulocytes leave the bone marrow. This happens because the reserve of ready red blood cells is insufficient to replace blood loss, and it takes time for new ones to mature. Due to this circumstance, the bone marrow “releases” slightly “immature” reticulocytes, which, however, can already perform the main function of transporting oxygen and carbon dioxide.

What shape are red blood cells?

For detailed information about the causes of low hemoglobin (anenmia), read the article: Anemia

Leukocytes, types of leukocytes - lymphocytes, neutrophils, eosinophils, basophils, monocyte. Structure and functions of various types of leukocytes.

Granulocytes include:

Neutrophil, appearance, structure and functions

First of all, let’s find out why the neutrophil is called that. In the cytoplasm of this cell there are granules that are stained with dyes that have a neutral reaction (pH = 7.0). That is why this cell was named so: neutrophil - it has an affinity for neutral dyes. These neutrophil granules have the appearance of fine grains of violet-brown color.

The neutrophil has a round shape and an unusual nuclear shape. Its core is a rod or 3 to 5 segments connected to each other by thin cords. A neutrophil with a rod-shaped nucleus (rod) is a “young” cell, and a neutrophil with a segmented nucleus (segmented) is a “mature” cell. In the blood, the majority of neutrophils are segmented (up to 65%), while band neutrophils normally make up only up to 5%.

What happens to the neutrophil after it matures in the bone marrow? A mature neutrophil lives in the bone marrow for 5 days, after which it enters the blood, where it lives in the vessels for 8–10 hours. Moreover, the bone marrow pool of mature neutrophils is 10–20 times larger than the vascular pool. From the vessels they go into the tissues, from which they no longer return to the blood. Neutrophils live in tissues for 2–3 days, after which they are destroyed in the liver and spleen. So, a mature neutrophil lives only 14 days.

There are about 250 types of granules in the neutrophil cytoplasm. These granules contain special substances that help the neutrophil perform its functions. What is contained in the granules? First of all, these are enzymes, bactericidal substances (destroying bacteria and other pathogenic agents), as well as regulatory molecules that control the activity of neutrophils themselves and other cells.

What does a neutrophil do? What is its purpose? The main role of the neutrophil is protective. This protective function is realized through the ability of phagocytosis. Phagocytosis is a process during which a neutrophil approaches a pathogenic agent (bacteria, virus), captures it, places it inside itself and, using the enzymes of its granules, kills the microbe. One neutrophil is capable of absorbing and neutralizing 7 microbes. In addition, this cell is involved in the development of the inflammatory response. Thus, the neutrophil is one of the cells that provides human immunity. The neutrophil works by performing phagocytosis in blood vessels and tissues.

Eosinophils, appearance, structure and functions

The eosinophil, like the neutrophil, has a round shape and a rod-shaped or segmented nucleus. The granules located in the cytoplasm of this cell are quite large, of the same size and shape, and are painted bright orange, reminiscent of red caviar. Eosinophil granules are stained with dyes that have an acidic reaction (pH 7). And the entire cell is named so because it has an affinity for basic dyes: basophil - basic.

Basophil is also formed in the bone marrow from a precursor cell - the basophilic myeloblast. During the maturation process, it goes through the same stages as the neutrophil and eosinophil. Basophil granules contain enzymes, regulatory molecules, and proteins involved in the development of the inflammatory response. After full maturation, basophils enter the blood, where they live for no more than two days. Next, these cells leave the bloodstream and go into the tissues of the body, but what happens to them there is currently unknown.

During circulation in the blood, basophils participate in the development of the inflammatory response, are able to reduce blood clotting, and also take part in the development of anaphylactic shock (a type of allergic reaction). Basophils produce a special regulatory molecule interleukin IL-5, which increases the number of eosinophils in the blood.

Monocyte, appearance, structure and functions

A monocyte is an agranulocyte, that is, there is no granularity in this cell. It is a large cell, slightly triangular in shape, has a large nucleus, which can be round, bean-shaped, lobed, rod-shaped and segmented.

After this, some of the monocytes die, and some go into the tissues, where they are slightly modified - “ripe” and become macrophages. Macrophages are the largest cells in the blood and have an oval or round nucleus. The cytoplasm is blue in color with many vacuoles (voids) that give it a foamy appearance.

What functions do these cells perform? The blood monocyte produces various enzymes and regulatory molecules, and these regulatory molecules can contribute to both the development of inflammation and, conversely, inhibit the inflammatory response. What should a monocyte do at this particular moment and in a certain situation? The answer to this question does not depend on him; the need to strengthen or weaken the inflammatory reaction is accepted by the body as a whole, and the monocyte only carries out the command. In addition, monocytes are involved in wound healing, helping to speed up this process. They also promote the restoration of nerve fibers and bone tissue growth. The macrophage in tissues is focused on performing a protective function: it phagocytoses pathogenic agents and suppresses the reproduction of viruses.

Lymphocyte appearance, structure and functions

A lymphocyte is a round cell of various sizes with a large round nucleus. A lymphocyte is formed from a lymphoblast in the bone marrow, like other blood cells, and divides several times during maturation. However, in the bone marrow the lymphocyte undergoes only “general preparation”, after which it finally matures in the thymus, spleen and lymph nodes. This maturation process is necessary because a lymphocyte is an immunocompetent cell, that is, a cell that provides all the diversity of the body’s immune reactions, thereby creating its immunity.

A lymphocyte that has undergone “special training” in the thymus is called a T - lymphocyte, in the lymph nodes or spleen - B - lymphocyte. T - lymphocytes are smaller in size than B - lymphocytes. The ratio of T and B cells in the blood is 80% and 20%, respectively. For lymphocytes, blood is a transport medium that delivers them to the place in the body where they are needed. A lymphocyte lives on average 90 days.

The main function of both T- and B-lymphocytes is protective, which is carried out through their participation in immune reactions. T lymphocytes predominantly phagocytose pathogenic agents, destroying viruses. Immune reactions carried out by T lymphocytes are called nonspecific resistance. It is nonspecific because these cells act equally against all pathogenic microbes.

B lymphocytes, on the contrary, destroy bacteria by producing specific molecules against them - antibodies. For each type of bacteria, B lymphocytes produce special antibodies that can destroy only this type of bacteria. This is why B lymphocytes form specific resistance. Nonspecific resistance is mainly directed against viruses, and specific resistance is directed mainly against bacteria.

After B lymphocytes have once encountered a microbe, they are able to form memory cells. It is the presence of such memory cells that determines the body’s resistance to infection caused by this bacteria. Therefore, in order to form memory cells, vaccinations against especially dangerous infections are used. In this case, a weakened or dead microbe is introduced into the human body in the form of a vaccination, the person becomes ill in a mild form, as a result, memory cells are formed, which ensure the body’s resistance to this disease throughout life. However, some memory cells last a lifetime, and some live for a certain period of time. In this case, vaccinations are given several times.

What is the composition of blood

The composition of blood is a combination of cellular elements and plasma. The cellular elements of blood are organic and chemical compounds, and plasma is a light yellow liquid substance that connects cells. Blood is a special type of connective tissue in the human body, which includes platelets, erythrocytes and leukocytes. It, like any tissue, performs certain functions in the human body: protective, respiratory, transport and regulatory. Its total volume in the human body is 4-5 liters.

Components

The formed elements of blood are platelets, erythrocytes and leukocytes, which are continuously produced in the human red bone marrow. Each blood cell performs a specific function in the circulatory system and in the human body as a whole. Platelets are platelets of blood that have cells without a nucleus, round in shape and colorless. Platelets are formed in the red bone marrow, a process called thrombopoiesis.

Platelets play an important role in the blood clotting process. If a person receives an open wound, the structure of platelets is disrupted and bleeding occurs. But when platelets enter the plasma, clotting occurs. There are from 200 to 400 thousand platelets per liter of blood in the human body.

Red blood cells are red, disc-shaped blood cells that, like platelets, do not have a nucleus. Red blood cells are produced in the body's red bone marrow, a process called erythropoiesis. During the process of formation and ripening, red blood cells lose their cell nucleus, due to which they enter the human circulatory system.

There are 5 million red blood cells per 1 mm3. From the moment a new red blood cell is formed until the next one appears, approximately a day passes, i.e., red blood cells change cyclically in the human body. Hemoglobin is a pigment in red blood cells that carries oxygen to tissue cells from the human lungs, after which it is decomposed into chemical compounds.

The following elements are leukocytes. Leukocytes are white blood cells that have a nucleus but do not have a permanent shape. The process of formation of leukocytes occurs in the lymph nodes, in the red bone marrow and in the spleen and is called leukopoiesis. There are from 6 to 8 thousand leukocytes per 1 mm3. From the moment of formation to the replacement of leukocytes, 2 to 4 days pass, i.e. The lifespan of these bodies is the shortest. The process of destruction of leukocyte cells occurs in the spleen, where they die and are converted into enzymes. The blood contains phagocytes. These are cells of the human immune system, which, in the process of circulation throughout the human body, bind and destroy foreign cells, bacteria and viruses, performing cleansing functions from microbes and foreign bacteria.

The chemical composition of blood depends on a person’s lifestyle, the presence of diseases, food, environmental factors; its composition is influenced by the physiological and age-related characteristics of the human body. The composition of the blood of a newborn child and an adult is significantly different, this is due to physiological factors in the development of the human body. The table shows the norm of indicators of formed elements.

Plasma and its composition

Another main element of blood is plasma. The volume of blood in the human body is from 4 to 5 liters, plasma occupies about 60% of the blood composition. Blood plasma has a liquid composition, and the color is transparent yellow or transparent white. If we analyze the chemical composition of blood plasma, it can be noted that plasma contains salts, electrolytes, lipids, hormones, organic acids and bases, vitamins and nitrogen. The mineral composition of plasma is compounds of Na, K, Ca, Mg ions and salts CaCl2, NaCl, NaH2PO4.

Plasma consists of 90% water, 7% organic and mineral substances, up to 7% proteins, the rest - fats and glucose. If plasma cells lose fluid, the level of salts increases, red blood cells lose their ability to transport useful substances and die, in some cases hemoglobin enters the plasma.

The functions of plasma proteins are varied. They take part in the creation of osmotic pressure and in the coagulation process, and contribute to the normalization of viscosity.

It is very important for the human body to keep the chemical properties of blood plasma normal in order to prevent loss of water in the plasma under the influence of toxic substances, increased levels of salts, hormones and acids, which affects the exchange of red blood cells and reduces the level of coagulation. The composition of a person’s blood may differ from person to person; this is influenced by gender, developmental characteristics of the human body and the person’s age.

Functions of blood cells

As already mentioned, in human blood there are cells of a certain composition and quantity that are produced by the body and disintegrate in it, performing certain functions at the cellular level. The composition and functions of blood depend on the lifestyle and physiological characteristics of a person; it changes indicators depending on internal and external influences on the functioning of the body. The main functions of blood, which are performed by erythrocytes, leukocytes, platelets, plasma and phagocytes, are transport, homeostatic and protective functions.

1. The transport function of blood plays an important role in human life. It ensures the transfer of useful substances throughout the body. Thanks to the circulatory system, every capillary, vein, artery and human organs are saturated with substances necessary for life. Substances contained in the blood are transported in pure form and enter into chemical reactions with other substances, forming complex organic, mineral and vitamin compounds.
2. The respiratory function of the blood provides tissues and organs, carrying oxygen from the lungs. Waste oxygen in the form of carbon dioxide is transported back to the lungs by the blood using red blood cells.
3. The excretory function is to relieve negative compounds in the human body and remove them through the excretory systems and organs.
4. The nutritional function ensures the saturation of cells and organs with useful substances and oxygen and activates the body’s immune forces.
5. The regulatory function is to balance between the compositions of useful and waste substances and compounds in the human body. The blood carries useful substances to organs and systems, and removes waste compounds and cells from the body. White blood cells play a major role in the process of binding and destroying foreign cells in the human body.
6. The trophic function provides the organs with useful substances that are absorbed by the intestinal walls.
7. The protective function of blood includes phagocytic, hemostatic and immune functions. The phagocytic function has a binding effect on foreign microorganisms and cells, absorbing them into healthy cells. When infections, viruses or bacteria enter the body, the blood immediately reacts to this, trying to neutralize their presence. Having had rubella once, you develop immunity from this disease. Thanks to this, the person will not get sick a second time. If the blood loses its natural immunity over time, as with diphtheria, it is restored artificially (by vaccination). Hemostatic function is provided by platelets. It consists of stopping bleeding and providing clotting in case of wounds and other disorders of the body. The homeostatic function ensures the maintenance of certain processes within the circulatory system, namely: maintaining pH balance, maintaining and stabilizing the internal temperature of the body and organs, maintaining osmotic pressure. The protective function is provided by leukocytes, platelets and phagocytes.

Physical and chemical properties of blood

The physical and chemical properties of blood include color, specific gravity and viscosity, suspension properties, and osmotic properties. What does this mean? The color is determined by the concentration of hemoglobin in it. So, in the central veins and arteries, the blood has a bright, saturated color, and in the capillaries it has a weak color. This is due to the level of hemoglobin. From a school biology course we know that the higher the hemoglobin level, the brighter and more saturated the color becomes.

Specific gravity or density. Density is determined by the number of red blood cells. The more red blood cells there are in the blood, the better the nutrients are absorbed. The approximate density is 1.051 -1.062. The plasma density indicator is approximately from 1.029 to 1.032 units. Viscosity is formed during the interaction of plasma with micromolecules of colloids and formed elements. Blood viscosity is 2 times higher than plasma viscosity.

Blood and its suspension properties depend on the erythrocyte sedimentation rate; the more albumins contained in the composition, the higher its suspension properties. Osmotic pressure ensures the regulation and exchange of water in the blood and connective tissues. With increased osmotic pressure, the penetration of water into the cells will be higher, and with reduced pressure, vice versa.

Blood groups

There are 4 groups and each of them has certain elements and composition. The blood type and composition are determined by a biochemical analysis at the birth of the child. The group is determined at birth based on protein levels in red blood cells and plasma. This indicator remains unchanged throughout a person’s life. But in some cases a mixture of blood is possible. This happens during transfusions during injuries, blood loss and operations.

The person who gives his blood is called a donor, and the one who receives it is called a recipient. During the transfusion process, doctors are guided by the principles of group compatibility. Each group is complete, but not all of them can be mixed. This is due to the presence or absence of agglutinin in the plasma, which contributes to the gluing of red blood cells with the same characteristics. There are compatibility standards for transfusion. The main characteristic of blood of the first group is its versatility, because it is suitable for transfusion to representatives of the other three groups.

The second group can be used for transfusion to people with the second and fourth groups. The third group can only be transfused to people with the third or fourth group. The fourth group is allowed to be transfused to people with the same group. For people who have the first group, only the first group is used for transfusion.

If transfusion groups are mismatched, there is a risk of red blood cells sticking together, causing their destruction and death of the patient. The value of blood is priceless because it is the main fluid of the body, which provides all the vital processes of human life.

Blood cells and their functions

Human blood is a liquid substance consisting of plasma and formed elements, or blood cells, suspended in it, which make up approximately 100% of the total volume. They are small in size and can only be seen under a microscope.

All blood cells are divided into red and white. The first are erythrocytes, which make up the majority of all cells, the second are leukocytes.

Platelets are also considered to be blood cells. These small blood platelets are not actually full-fledged cells. They are small fragments separated from large cells - megakaryocytes.

Red blood cells

Red blood cells are called red blood cells. This is the most numerous group of cells. They carry oxygen from the respiratory organs to the tissues and take part in the transport of carbon dioxide from the tissues to the lungs.

The place of formation of red blood cells is the red bone marrow. They live for 120 days and are destroyed in the spleen and liver.

They are formed from precursor cells - erythroblasts, which, before becoming an erythrocyte, go through different stages of development and divide several times. Thus, up to 64 red blood cells are formed from the erythroblast.

Red blood cells lack a nucleus and are shaped like a disk concave on both sides, the diameter of which is on average about 7-7.5 microns, and the thickness at the edges is 2.5 microns. This shape increases the ductility required for passage through small vessels and the surface area for gas diffusion. Old red blood cells lose their plasticity, which is why they linger in the small vessels of the spleen and are destroyed there.

Most red blood cells (up to 80%) have a biconcave spherical shape. The remaining 20% ​​may have another: oval, cup-shaped, simple spherical, sickle-shaped, etc. Violation of the shape is associated with various diseases (anemia, deficiency of vitamin B 12, folic acid, iron, etc.).

Most of the cytoplasm of the red blood cell is occupied by hemoglobin, consisting of protein and heme iron, which gives the blood its red color. The non-protein part consists of four heme molecules with an Fe atom in each. It is thanks to hemoglobin that the red blood cell is able to carry oxygen and remove carbon dioxide. In the lungs, an iron atom binds with an oxygen molecule, hemoglobin turns into oxyhemoglobin, which gives the blood a scarlet color. In tissues, hemoglobin gives up oxygen and adds carbon dioxide, turning into carbohemoglobin, as a result the blood becomes dark. In the lungs, carbon dioxide is separated from hemoglobin and removed by the lungs to the outside, and the incoming oxygen is again associated with iron.

In addition to hemoglobin, the cytoplasm of the erythrocyte contains various enzymes (phosphatase, cholinesterase, carbonic anhydrase, etc.).

The erythrocyte membrane has a fairly simple structure compared to the membranes of other cells. It is an elastic thin mesh, which ensures rapid gas exchange.

In the blood of a healthy person, there may be small amounts of immature red blood cells called reticulocytes. Their number increases with significant blood loss, when replacement of red cells is required and the bone marrow does not have time to produce them, so it releases immature ones, which are nevertheless capable of performing the functions of red blood cells in transporting oxygen.

Leukocytes

Leukocytes are white blood cells whose main task is to protect the body from internal and external enemies.

They are usually divided into granulocytes and agranulocytes. The first group is granular cells: neutrophils, basophils, eosinophils. The second group does not have granules in the cytoplasm; it includes lymphocytes and monocytes.

Neutrophils

This is the most numerous group of leukocytes - up to 70% of the total number of white cells. Neutrophils got their name due to the fact that their granules are stained with dyes with a neutral reaction. Its grain size is fine, the granules have a purple-brownish tint.

The main task of neutrophils is phagocytosis, which consists of capturing pathogenic microbes and tissue breakdown products and destroying them inside the cell with the help of lysosomal enzymes located in granules. These granulocytes fight mainly bacteria and fungi and to a lesser extent viruses. Pus consists of neutrophils and their remains. Lysosomal enzymes are released during the breakdown of neutrophils and soften nearby tissues, thus forming a purulent focus.

A neutrophil is a rounded nuclear cell, reaching a diameter of 10 microns. The core may have the shape of a rod or consist of several segments (from three to five) connected by cords. An increase in the number of segments (up to 8-12 or more) indicates pathology. Thus, neutrophils can be band or segmented. The first are young cells, the second are mature. Cells with a segmented nucleus make up up to 65% of all leukocytes, and band cells in the blood of a healthy person make up no more than 5%.

The cytoplasm contains about 250 types of granules containing substances through which the neutrophil performs its functions. These are protein molecules that affect metabolic processes (enzymes), regulatory molecules that control the work of neutrophils, substances that destroy bacteria and other harmful agents.

These granulocytes are formed in the bone marrow from neutrophilic myeloblasts. A mature cell stays in the brain for 5 days, then enters the blood and lives here for up to 10 hours. From the vascular bed, neutrophils enter the tissues, where they remain for two to three days, then they enter the liver and spleen, where they are destroyed.

Basophils

There are very few of these cells in the blood - no more than 1% of the total number of leukocytes. They have a round shape and a segmented or rod-shaped nucleus. Their diameter reaches 7-11 microns. Inside the cytoplasm there are dark purple granules of varying sizes. They got their name due to the fact that their granules are colored with dyes with an alkaline, or basic, reaction. Basophil granules contain enzymes and other substances involved in the development of inflammation.

Their main function is the release of histamine and heparin and participation in the formation of inflammatory and allergic reactions, including the immediate type (anaphylactic shock). In addition, they can reduce blood clotting.

They are formed in the bone marrow from basophilic myeloblasts. After maturation, they enter the blood, where they remain for about two days, then go into the tissues. What happens next is still unknown.

Eosinophils

These granulocytes make up approximately 2-5% of the total number of white cells. Their granules are stained with an acidic dye, eosin.

They have a rounded shape and a slightly colored core, consisting of segments of the same size (usually two, less often three). Eosinophils reach µm in diameter. Their cytoplasm is painted pale blue and is almost invisible among the large number of large round granules of yellow-red color.

These cells are formed in the bone marrow, their precursors are eosinophilic myeloblasts. Their granules contain enzymes, proteins and phospholipids. A mature eosinophil lives in the bone marrow for several days, after entering the blood it remains in it for up to 8 hours, then moves to tissues that have contact with the external environment (mucous membranes).

These are round cells with a large nucleus occupying most of the cytoplasm. Their diameter is 7 to 10 microns. The kernel can be round, oval or bean-shaped and has a rough structure. Consists of lumps of oxychromatin and basiromatin, resembling blocks. The core can be dark purple or light purple, sometimes it contains light inclusions in the form of nucleoli. The cytoplasm is colored light blue; around the nucleus it is lighter. In some lymphocytes, the cytoplasm has azurophilic granularity, which turns red when stained.

Two types of mature lymphocytes circulate in the blood:

• Narrow plasma. They have a rough dark purple nucleus and a narrow blue rim of cytoplasm.
• Wide-plasma. In this case, the kernel has a paler color and bean-shaped shape. The rim of the cytoplasm is quite wide, gray-blue in color, with rare ausurophilic granules.

From atypical lymphocytes in the blood you can find:

• Small cells with barely visible cytoplasm and a pyknotic nucleus.
• Cells with vacuoles in the cytoplasm or nucleus.
• Cells with lobed, kidney-shaped, jagged nuclei.
• Bare kernels.

Lymphocytes are formed in the bone marrow from lymphoblasts and undergo several stages of division during the process of maturation. Its complete maturation occurs in the thymus, lymph nodes and spleen. Lymphocytes are immune cells that mediate immune responses. There are T-lymphocytes (80% of the total) and B-lymphocytes (20%). The former matured in the thymus, the latter in the spleen and lymph nodes. B lymphocytes are larger in size than T lymphocytes. The lifespan of these leukocytes is up to 90 days. Blood for them is a transport medium through which they enter tissues where their help is required.

The actions of T-lymphocytes and B-lymphocytes are different, although both take part in the formation of immune reactions.

The former are engaged in the destruction of harmful agents, usually viruses, through phagocytosis. The immune reactions in which they participate are nonspecific resistance, since the actions of T lymphocytes are the same for all harmful agents.

Based on the actions they perform, T-lymphocytes are divided into three types:

• T-helpers. Their main task is to help B-lymphocytes, but in some cases they can act as killers.
• T-killers. Destroy harmful agents: foreign, cancerous and mutated cells, infectious agents.
• T-suppressors. Inhibit or block overly active reactions of B-lymphocytes.

B-lymphocytes act differently: against pathogens they produce antibodies - immunoglobulins. This happens as follows: in response to the actions of harmful agents, they interact with monocytes and T-lymphocytes and turn into plasma cells that produce antibodies that recognize the corresponding antigens and bind them. For each type of microbe, these proteins are specific and are capable of destroying only a certain type, therefore the resistance that these lymphocytes form is specific, and it is directed primarily against bacteria.

These cells provide the body's resistance to certain harmful microorganisms, which is commonly called immunity. That is, having encountered a harmful agent, B-lymphocytes create memory cells that form this resistance. The same thing - the formation of memory cells - is achieved by vaccinations against infectious diseases. In this case, a weak microbe is introduced so that the person can easily survive the disease, and as a result, memory cells are formed. They can remain for life or for a certain period, after which the vaccination must be repeated.

Monocytes

Monocytes are the largest of the leukocytes. Their number ranges from 2 to 9% of all white blood cells. Their diameter reaches 20 microns. The monocyte nucleus is large, occupies almost the entire cytoplasm, can be round, bean-shaped, mushroom-shaped, or butterfly-shaped. When stained it turns red-violet. The cytoplasm is smoky, bluish-smoky, less often blue. It usually has an azurophilic fine grain size. It may contain vacuoles (voids), pigment grains, and phagocytosed cells.

Monocytes are produced in the bone marrow from monoblasts. After maturation, they immediately appear in the blood and remain there for up to 4 days. Some of these leukocytes die, some move into the tissue, where they mature and turn into macrophages. These are the largest cells with a large round or oval nucleus, blue cytoplasm and a large number of vacuoles, which is why they appear foamy. The lifespan of macrophages is several months. They can be constantly in one place (resident cells) or move (wandering).

Monocytes form regulatory molecules and enzymes. They are able to form an inflammatory response, but can also inhibit it. In addition, they participate in the wound healing process, helping to speed it up, and promote the restoration of nerve fibers and bone tissue. Their main function is phagocytosis. Monocytes destroy harmful bacteria and inhibit the proliferation of viruses. They are able to carry out commands, but cannot distinguish between specific antigens.

Platelets

These blood cells are small, anucleate plates and can be round or oval in shape. During activation, when they are near the damaged vessel wall, they form outgrowths, so they look like stars. Platelets contain microtubules, mitochondria, ribosomes, and specific granules containing substances necessary for blood clotting. These cells are equipped with a three-layer membrane.

Platelets are produced in the bone marrow, but in a completely different way than other cells. Blood plates are formed from the largest cells of the brain - megakaryocytes, which, in turn, were formed from megakaryoblasts. Megakaryocytes have a very large cytoplasm. After the cell matures, membranes appear in it, dividing it into fragments that begin to separate, and thus platelets appear. They leave the bone marrow into the blood, stay in it for 8-10 days, then die in the spleen, lungs, and liver.

Blood plates can have different sizes:

• the smallest are microforms, their diameter does not exceed 1.5 microns;
• normoforms reach 2-4 microns;
• macroforms – 5 microns;
• megaloforms – 6-10 microns.

Platelets perform a very important function - they participate in the formation of a blood clot, which closes the damage in the vessel, thereby preventing blood from leaking out. In addition, they maintain the integrity of the vessel wall and promote its rapid recovery after damage. When bleeding begins, platelets adhere to the edge of the injury until the hole is completely closed. The adhered plates begin to break down and release enzymes that affect the blood plasma. As a result, insoluble fibrin threads are formed, tightly covering the injury site.

Conclusion

Blood cells have a complex structure, and each type performs a specific job: from transporting gases and substances to producing antibodies against foreign microorganisms. Their properties and functions have not been fully studied to date. For normal human life, a certain amount of each type of cell is necessary. Based on their quantitative and qualitative changes, doctors have the opportunity to suspect the development of pathologies. The composition of the blood is the first thing that a doctor studies when treating a patient.

Human blood cells. The structure of blood cells

In the anatomical structure of the human body, there are cells, tissues, organs and organ systems that carry out all vital functions. There are about 11 such systems in total:

• nervous (CNS);
• digestive;
• cardiovascular;
• hematopoietic;
• respiratory;
• musculoskeletal;
• lymphatic;
• endocrine;
• excretory;
• sexual;
• musculocutaneous.

Each of them has its own characteristics, structure and performs certain functions. We will consider that part of the circulatory system that is its basis. We will talk about the liquid tissue of the human body. Let's study the composition of blood, blood cells and their significance.

Anatomy of the human cardiovascular system

The most important organ that forms this system is the heart. It is this muscle pouch that plays a fundamental role in blood circulation throughout the body. Blood vessels of different sizes and directions depart from it, which are divided into:

• veins;
• arteries;
• aorta;
• capillaries.

The listed structures carry out constant circulation of a special tissue of the body - blood, which washes all cells, organs and systems as a whole. In humans (as in all mammals), there are two circles of blood circulation: large and small, and such a system is called closed.

Its main functions are as follows:

• gas exchange - the transport (that is, movement) of oxygen and carbon dioxide;
• nutritional, or trophic - delivery of necessary molecules from the digestive organs to all tissues, systems, and so on;
• excretory - removal of harmful and waste substances from all structures to the excretory;
• delivery of endocrine system products (hormones) to all cells of the body;
• protective - participation in immune reactions through special antibodies.

Obviously the functions are very significant. This is why the structure of blood cells, their role and general characteristics are so important. After all, blood is the basis for the activity of the entire corresponding system.

Composition of blood and the significance of its cells

What is this red liquid with a specific taste and smell that appears on any part of the body at the slightest injury?

By its nature, blood is a type of connective tissue consisting of a liquid part - plasma and formed elements of cells. Their percentage ratio is approximately 60/40. In total, there are about 400 different compounds in the blood, both hormonal in nature and vitamins, proteins, antibodies and microelements.

The volume of this fluid in the body of an adult is about 5.5-6 liters. Losing 2-2.5 of them is deadly. Why? Because blood performs a number of vital functions.

1. Provides homeostasis of the body (constancy of the internal environment, including body temperature).
2. The work of blood and plasma cells leads to the distribution of important biologically active compounds throughout all cells: proteins, hormones, antibodies, nutrients, gases, vitamins, as well as metabolic products.
3. Due to the constant composition of the blood, a certain level of acidity is maintained (pH should not exceed 7.4).
4. It is this tissue that takes care of removing excess, harmful compounds from the body through the excretory system and sweat glands.
5. Liquid solutions of electrolytes (salts) are excreted in the urine, which is ensured solely by the work of the blood and excretory organs.

It is difficult to overestimate the importance of human blood cells. Let us consider in more detail the structure of each structural element of this important and unique biological fluid.

Plasma

A viscous liquid of a yellowish color, occupying up to 60% of the total blood mass. The composition is very diverse (several hundred substances and elements) and includes compounds from various chemical groups. So, this part of the blood includes:

• Protein molecules. It is believed that every protein that exists in the body is initially present in the blood plasma. There are especially many albumins and immunoglobulins, which play an important role in protective mechanisms. In total, about 500 names of plasma proteins are known.
• Chemical elements in the form of ions: sodium, chlorine, potassium, calcium, magnesium, iron, iodine, phosphorus, fluorine, manganese, selenium and others. Almost the entire Mendeleev Periodic System is present here, approximately 80 items from it are found in the blood plasma.
• Mono-, di- and polysaccharides.
• Vitamins and coenzymes.
• Hormones of the kidneys, adrenal glands, gonads (adrenaline, endorphin, androgens, testosterones and others).
• Lipids (fats).
• Enzymes as biological catalysts.

The most important structural parts of plasma are blood cells, of which there are 3 main types. They are the second component of this type of connective tissue; their structure and functions deserve special attention.

Red blood cells

The smallest cellular structures, the dimensions of which do not exceed 8 microns. However, their number is over 26 trillion! - makes you forget about the insignificant volumes of an individual particle.

Red blood cells are blood cells that are structures devoid of the usual constituent parts. That is, they have no nucleus, no EPS (endoplasmic reticulum), no chromosomes, no DNA, and so on. If you compare this cell with anything, then a biconcave porous disk - a kind of sponge - is best suited. The entire internal part, each pore, is filled with a specific molecule - hemoglobin. This is a protein whose chemical basis is an iron atom. It is easily able to interact with oxygen and carbon dioxide, which is the main function of red blood cells.

That is, red blood cells are simply filled with hemoglobin in the amount of 270 million per cell. Why red? Because it is precisely this color that gives them iron, which forms the basis of protein, and due to the overwhelming majority of red blood cells in human blood, it acquires the corresponding color.

In appearance, when viewed through a special microscope, red blood cells are rounded structures, seemingly flattened from the top and bottom to the center. Their precursors are stem cells produced in the bone marrow and spleen depot.

Function

The role of red blood cells is explained by the presence of hemoglobin. These structures collect oxygen in the pulmonary alveoli and distribute it to all cells, tissues, organs and systems. At the same time, gas exchange occurs, because by giving up oxygen, they take away carbon dioxide, which is also transported to the places of excretion - the lungs.

At different ages, the activity of red blood cells is not the same. For example, the fetus produces special fetal hemoglobin, which transports gases an order of magnitude more intensively than the usual one characteristic of adults.

There is a common disease that is caused by red blood cells. Blood cells produced in insufficient quantities lead to anemia - a serious disease of general weakening and thinning of the body's vital forces. After all, the normal supply of oxygen to tissues is disrupted, which causes their starvation and, as a result, rapid fatigue and weakness.

The lifespan of each red blood cell is from 90 to 100 days.

Platelets

Another important human blood cell is platelets. These are flat structures, the size of which is 10 times smaller than red blood cells. Such small volumes allow them to quickly accumulate and stick together to fulfill their intended purpose.

There are about 1.5 trillion of these guardians of order in the body, the number is constantly replenished and renewed, since their lifespan, alas, is very short - only about 9 days. Why law enforcement officers? This is due to the function they perform.

Meaning

Orienting themselves in the parietal vascular space, blood cells, platelets, carefully monitor the health and integrity of organs. If suddenly a tissue rupture occurs somewhere, they react immediately. By sticking together, they seem to seal the damaged area and restore the structure. In addition, they are largely responsible for blood clotting on the wound. Therefore, their role is precisely to ensure and restore the integrity of all vessels, integuments, and so on.

Leukocytes

White blood cells, which got their name for their absolute colorlessness. But the lack of coloring does not in any way diminish their significance.

Round-shaped bodies are divided into several main types:

The sizes of these structures are quite significant compared to erythrocytes and platelets. They reach 23 microns in diameter and live only a few hours (up to 36). Their functions vary depending on the variety.

White blood cells live not only in it. In fact, they only use liquid to get to the required destination and perform their functions. Leukocytes are found in many organs and tissues. Therefore, their specific amount in the blood is small.

Role in the body

The general significance of all varieties of white bodies is to provide protection against foreign particles, microorganisms and molecules.

These are the main functions that white blood cells perform in the human body.

Stem cells

The lifespan of blood cells is insignificant. Only some types of leukocytes responsible for memory can exist throughout life. Therefore, the body has a hematopoietic system, consisting of two organs and ensuring the replenishment of all formed elements.

These include:

Bone marrow is especially important. It is located in the cavities of flat bones and produces absolutely all blood cells. In newborns, tubular formations (lower leg, shoulder, hands and feet) also take part in this process. With age, such brain remains only in the pelvic bones, but it is enough to provide the entire body with formed blood elements.

Another organ that does not produce, but stores quite large quantities of blood cells for emergencies, is the spleen. This is a kind of “blood depot” of every human body.

Why are stem cells needed?

Blood stem cells are the most important undifferentiated formations that play a role in hematopoiesis - the formation of the tissue itself. Therefore, their normal functioning is the key to health and high-quality functioning of the cardiovascular and all other systems.

In cases where a person loses a large amount of blood, which the brain itself cannot or does not have time to replenish, selection of donors is necessary (this is also necessary in the case of blood renewal in leukemia). This process is complex and depends on many features, for example, on the degree of relationship and the comparability of people with each other in other respects.

Blood cell norms in medical analysis

For a healthy person, there are certain norms for the amount of formed blood elements per 1 mm 3 . These indicators are as follows:

1. Red blood cells - 3.5-5 million, protein hemoglobin g/l.
2. Thrombocytes thousand
3. Leukocytes - from 2 to 5 thousand.

These rates may vary depending on the person's age and health. That is, blood is an indicator of the physical condition of people, so its timely analysis is the key to successful and high-quality treatment.

Blood cells

Article by professional biology tutor T. M. Kulakova

Erythrocytes are red blood cells, biconcave in shape. When mature they have no nuclei. Red blood cell cells also lack mitochondria, which causes them to respire anaerobically. These cells are elastic (can fold in half), which allows them to squeeze through capillaries whose lumen is smaller than the diameter of the red blood cell. The absence of a nucleus and the shape of a biconcave lens increase the surface of red blood cells, and ensures a high rate of oxygen diffusion into the red blood cell.

Red blood cells contain hemoglobin. It consists of a globin protein and a heme group. Heme contains an iron atom, which is capable of attaching and releasing oxygen. 1 cubic millimeter contains 4-5 million red blood cells. Red blood cells are born in the red bone marrow. Life expectancy is 120 days. They are destroyed in the spleen or liver. The iron released during this process is stored in the liver and can be reused in the formation of new red blood cells. The rest of the heme is broken down to form bile pigments, which are excreted as part of bile into the intestine.

Hemoglobin, which has added oxygen, turns into oxyhemoglobin. Arterial blood is bright scarlet.

Hemoglobin with carbon dioxide attached is called carbhemoglobin. Venous blood is dark cherry in color.

Hemoglobin with carbon monoxide attached is called carboxyhemoglobin. This is a stable connection. Such hemoglobin is unable to attach oxygen, which is life-threatening.

Anemia (anemia) is a condition characterized by a reduced content of red blood cells and hemoglobin. Occurs when there is a lack of iron and some other substances in the body - with significant blood loss, with dysfunction of the red bone marrow.

Leukocytes are colorless cells. They contain nuclei of various shapes. The cells themselves do not have a permanent shape. There are 4-9 thousand in 1 cubic millimeter of blood. leukocytes. Formed in red bone marrow.

There are two groups of leukocytes: granular and non-granular. The former have small grains (granules) in the cytoplasm; non-granular leukocytes do not have such grains.

The main function of leukocytes is to protect the body from bacteria, viruses, protozoa, foreign proteins, any foreign substances, i.e. they provide immunity.

Leukocytes can leave blood vessels and enter the intercellular space, moving between cells of various tissues of the body. Some leukocytes, having discovered a foreign body, capture it with pseudopods, absorb and destroy it.

The process of absorption and digestion of various microbes and foreign substances entering the body by leukocytes is called phagocytosis, and the leukocytes themselves are called phagocytes.

The phenomenon of phagocytosis was discovered by I. I. Mechnikov.

As a result of phagocytosis, the body is freed from dead cells.

The lifespan of leukocytes is 2-4 days (with the exception of lymphocytes, some of which live throughout a person’s life). They die in the liver, in the spleen, in places of inflammation.

Platelets, or blood platelets, are colorless, biconvex, anucleate cells. 1 cubic millimeter contains about 200 - 400 thousand platelets. The peculiarity of platelets is that they can change their shape and size depending on their location.

The chemical composition of these cells is very complex. Platelet enzymes are essential for the blood clotting process. The main function of platelets is their participation in the blood clotting process.

The lifespan of platelets is 5 – 7 days. They are destroyed in the liver and spleen.

Some exoplanets through the eyes of artists

Previously, it was believed that rocky planets must necessarily consist of three important layers - a shell, a mantle and a core containing a melt of the heaviest elements. This differentiation, according to the most authoritative theories, appeared already in the early stages of their evolution, when collisions with other celestial bodies were especially observed, and powerful radioactive processes were taking place on the planets themselves. All this heated up the young planets, and heavier elements settled closer to the center.

However, the discovery of planets far beyond our solar system, which has been very active in recent years, demonstrates a whole gallery of worlds that are very strange by our standards. Among them there is a planet consisting of a colossal diamond (“Trillions of Carats”), and a planet that managed to survive after being absorbed by a red giant (“Will to Live”), and even those that, in the opinion of astronomers, should not exist at all ("Exotic exoplanet"). And the group of astronomer Sara Seager has theoretically described another very exotic option - “nuclear-free” rocky planets.

Such exoplanets differentiate into two layers during their development without forming a core. This, according to scientists, can happen if, during the birth of a planet, it finds itself in an environment too rich in water. Iron interacts with it, forming an oxide faster than it can settle closer to the center of the planet in pure metallic form.

Note that today's technologies do not allow us to strictly confirm these theoretical calculations in practice. It is very difficult to see such small bodies at such vast distances, let alone study their chemical composition in detail.

But one thing can be said quite definitely about such “nuclear-free” bodies: there are unlikely to be brothers in mind on them, or indeed any life at all (at least in the form in which we are accustomed to imagine it). The fact is that it is the molten core of Earth-like planets that generates a powerful magnetic field around them, which reliably protects living organisms from a number of troubles - primarily from streams of charged particles with which the Sun constantly bombards the surrounding area. Such exposure can be deadly, causing both free radical reactions and dangerously high levels of mutagenicity.

By the way, Sarah Seeger's group has already appeared in our messages. Let us recall that it was these scientists who compiled their version of the summary table of all exoplanets: “

Do you think a cell can exist without a nucleus? Justify your answer.

In prokaryotes, circular DNA is located directly in the cytoplasm and successfully performs its functions. However, the structure and activity of a eukaryotic cell is much more complex than that of a prokaryotic cell. In this regard, eukaryotes need to have significantly more nucleic acids, which are more convenient to localize in a certain area. This problem was solved by the appearance of the nuclear membrane and the separation of the cell nucleus. In addition, the nuclear envelope protects chromatin from chemical and mechanical damage.

Can a eukaryotic cell exist without a nucleus? Almost all hereditary information about the structure of proteins is stored in the nucleus. Consequently, without a nucleus, the cell cannot develop and dies. However, some cells of a multicellular organism (for example, human red blood cells) lose their nucleus during growth and specialization; By the time the nucleus is lost, the entire necessary set of proteins has already been synthesized. The rate of destruction of these proteins determines the lifespan of such cells (usually several weeks).