The structure of human leukocytes. Features of the structure of leukocytes

Blood continuously circulates in the system of blood vessels. It performs very important functions in the body: respiratory, transport, protective and regulatory, ensuring the constancy of the internal environment of our body.

Blood is one of the connective tissues, which consists of a liquid intercellular substance having a complex composition. It includes plasma and cells suspended in it or the so-called uniform elements of blood: leukocytes, erythrocytes and platelets. It is known that 1 mm ^{3 of} blood contains leukocytes from 5 to 8 thousand, erythrocytes - from 4.5 to 5 million, and platelets - from 200 to 400 thousand.

The amount of blood in the body of a healthy person is about 4.5 to 5 liters. 55-60% of the volume is occupied by the plasma, and 40-45% of the total volume remains on the shaped elements. Plasma is a translucent yellowish liquid, which contains water (90%), organic and mineral substances, vitamins, amino acids, hormones, metabolic products.

Structure of leukocytes

Leukocytes are blood cells that have a colorless cytoplasm. They can be found in the blood plasma and in lymph. In general, they are white blood cells, they have nuclei, but they do not have a permanent shape. This is the peculiarity of the structure of leukocytes. These cells form in the spleen, lymph nodes, red bone marrow. Features of the structure of leukocytes determine the duration of their life, it is from 2 to 4 days. After that, they are destroyed in the spleen.

Leukocytes: structure and function

If we consider the functional and morphological signs of leukocytes, then we can say that they are ordinary cells that contain the nucleus and protoplasm. Their main function is to protect the body from harmful factors. The structure of leukocytes allows them to destroy foreign organisms that have entered the body, they also take an active part in various pathological, often very painful processes and various reactions (for example, the reaction of inflammation). But the structure of human leukocytes is diverse. Some of them have protoplasm of granular structure (granulocytes), others do not have granularity (agranulocytes). Consider these types of leukocytes in more detail.

The variety of leukocytes

As mentioned above, white blood cells are different, and they are divided into appearance, structure and functions. This is the peculiarity of the structure of human leukocytes.

So, the granulocytes are:

• Basophils;
• Neutrophils;
• Eosinophils.

Agranulocytes are represented by the following cell types:

• Lymphocytes;
• Monocytes.

Basophils

This is the smallest type of cells in the blood, their maximum 1% of the total number of leukocytes. The structure of leukocytes (and more specifically basophils) is simple. They are rounded, have a segmented or stab nucleus. The cytoplasm contains different in shape and size granules, having a dark purple color, in appearance they resemble black caviar. These granules are called basophilic granularity. They contain regulatory molecules, enzymes, proteins.

Basophils originate in the bone marrow, stem from the basophilic myeloblast cell. After full ripening, they go to the blood, the duration of their existence is no more than two days. After the cells go into the tissues of the body, but what happens to them later is still unknown.

In addition to participating in inflammatory reactions, basophils can reduce blood clotting and take an active part during the course of anaphylactic shock.

Neutrophils

Neutrophils in the blood are up to 70% of the total number of leukocytes. Their cytoplasm contains purple-brown granules that look like fine grains that can be stained with neutral reaction dyes.

Neutrophils are leukocytes whose cell structure is unusual. They are round in shape, but the nucleus is similar to a stick ("young" cell) or has 3-5 segments, which are connected together by thin strands (more "mature" cage).

All neutrophils are formed in the bone marrow from the neutrophilic myeloblast. A mature cell lives only 2 weeks, then it collapses in the spleen or liver.

Neutrophil in its cytoplasm has up to 250 kinds of granules. They all contain bactericidal substances, enzymes, regulatory molecules that help the neutrophil to perform its functions. They protect the body with phagocytosis (a process in which a neutrophil comes to a bacterium or a virus, captures it, moves it inside itself and, with the help of granule enzymes, destroys the pathogen). So, one cell of a neutrophil can neutralize up to 7 microbes. She is also involved in the inflammatory process.

Eosinophils

The structure of leukocytes is similar to each other. Eosinophil also has a rounded shape and a segmental or rod-shaped nucleus. In the cytoplasm of the cell there are large granules of the same shape and size, bright orange, resembling red caviar. They contain proteins, phospholipids and enzymes.

Eosinophil is formed in the bone marrow from the eosinophilic myeloblast. It exists from 8 to 15 days, then leaves in tissues that have contact with the external environment.

Eosinophil is also capable of phagositis, but only in other places (intestines, urogenital tract, mucous membranes of the respiratory tract). It still has to do with the emergence and development of allergic reactions.

Lymphocytes

Lymphocytes have a rounded shape and different sizes, as well as a large round nucleus. They appear in the bone marrow from the lymphoblast. The lymphocyte undergoes a special maturation process, since it is an immunocompetent cell. It is able to provide a variety of immune responses, creates immunity to the body.

Lymphocytes that are finally ripe in the thymus are T-lymphocytes, in the spleen or lymph nodes it is B-lymphocytes. The first cells are smaller in size. Between different types of lymphocytes there is a ratio of 80%: 20%, respectively. All cells live about 90 days.

The main function is protection, which is achieved through active participation in immune reactions. T-lymphocytes are involved in phagocytosis and immune reactions, which are called nonspecific resistance (in relation to all disease-causing viruses, these cells act the same way). But B-lymphocytes are capable of producing antibodies (specific molecules) in the process of killing bacteria. For each type of bacteria they produce special substances that can destroy only these harmful agents. B-lymphocytes provide specific resistance, which is directed primarily against bacteria, not viruses.

Monocyte

In the monocyte cell there is no granularity. This is a fairly large triangular cell, which has a large nucleus that can be bean-shaped, round, rod-shaped, lobed and segmented.

The monocyte arises from a monoblast in the bone marrow. In the blood, his life expectancy ranges from 48 to 96 hours. After that, some of the monocytes are destroyed, and the other part goes to the tissues, where "ripens", macrophages appear. Monocytes are the largest cells of blood, having a round or oval core, a blue cytoplasm with a large number of voids (vacuoles), which give it a foamy appearance.

Macrophages in the tissues of the body can live for several months, where they become wandering or resident cells (remain in the same place).

The monocyte is able to produce various regulatory molecules and enzymes that are capable of developing an inflammatory response or, conversely, to inhibit it. They also help to speed up the healing process of wounds. They promote the growth of bone tissue and the restoration of nerve fibers. The macrophage in the tissues performs a protective function. It suppresses the multiplication of viruses.

Erythrocytes

In the blood there are red blood cells and leukocytes. Their structure and functions are different from each other. The erythrocyte is a cell that has the shape of a biconcave disk. It does not contain a nucleus, and the bulk of the cytoplasm is occupied by a protein called hemoglobin. It consists of an iron atom and a protein part, has a complex structure. Hemoglobin carries oxygen in the body.

Erythrocytes appear in the bone marrow from erythroblast cells. Most of the erythrocytes are biconcave, and the others may differ. For example, they can be spherical, oval, nadkusannye, cup-shaped, etc. It is known that the shape of these cells can be violated due to various diseases. Each red blood cell is in the blood from 90 to 120 days, and then dies. Hemolysis is a phenomenon of erythrocyte destruction, which occurs mainly in the spleen, as well as in the liver and vessels.

Platelets

The structure of leukocytes and platelets is also different. Platelets do not have a nucleus, they are small cells of oval or round shape. If these cells are active, then they form outgrowths, they resemble a star. Platelets appear in the bone marrow from the megakaryoblast. They "work" only 8 to 11 days, then die in the liver, spleen or lungs.

The functions of platelets are very important. They are able to maintain the integrity of the vascular wall, restore it with damage. Platelets form a thrombus and thereby stop bleeding.