What is the life expectancy of thrombocytes? Life cycle of platelets

In the process of cell degeneration, platelets form in the bone marrow. These cells are responsible for the coagulation function of the blood and for the restoration of the walls of blood vessels.

Mature state

Talking about what is the duration of lifethrombocytes, most specialists take into account only the period when they have already separated into a separate structure from the megakaryocyte. The period when they are only being formed and ripening is not taken into account.

On average, they are in the circulatory systemabout a week. But the life span of human platelets can range from 5 to 12 days. Specialists distinguish several of their types: young, old, mature and forms of irritation. They depend not on the age of these cells, but on the characteristics of the hematopoiesis system.

Cycle of development

All platelets form in the bone marrow. Everything begins with a colony-forming megakaryocytic unit, it is also called "CFU-Meg". It shares mitosis. From it is formed first promegakarioblast, which turns into a megakaryoblast.

For 4-5 days in the bone marrow ripenspecial cells - megakaryocytes, whose diameter is about 60-120 microns. They are preceded by a special form with a non-grained basophilic cytoplasm and a tendency to polymorphism of the nucleus. It is called "promegakaryocyte". The ripe megakaryocyte is distinguished by the large dimensions of the cytoplasm and the presence of grains in it are violet-pink in color. The core in it is rough, it can be of various bizarre shapes.

It is from the cytoplasm of the megakaryocyte that they separatesmall blood cells that resemble discs in shape. From this moment it is already possible to talk about the life expectancy of platelets. Evaluate, as a rule, only mature forms. They are in the body of a healthy person should be about 90%.

Number of cells

To understand why in the blood such concentrationnuclear-free bodies, one must know not only what the life span of platelets is, but also about how fast and how much they appear. For each kilogram of human weight, they are about 15x10⁶. From each megakaryocyte in the process of divisionabout 3000 platelets are loosened. About 7-17% of the total is formed in the lungs. This is because prothrombocytes also enter the bloodstream. They independently reach the microcircular bed of the lungs. And already there is a process of platelet release.

Every day in the human body produces about 66 ± 14.6 thousand platelets per each μl of blood. The blood of an adult person should be between 180 and 320x10⁹ these blood cells, their children can be from 150 to 450x10⁹. But when calculating their number, one must take into account age. For example, in newborns who have not yet reached 10 days, they can be from 99 to 420x10⁹.

Appearance of plates

All mature calves have the same structure. The life expectancy of platelets in the blood can vary. Each of disc-shaped plates does not contain a nucleus, but it has a centrally located granulomer, which consists of azurophilic grains. They can be from 5 to 20. Also, the mature platelets are distinguished by the lilac hyalomer and the presence of clear boundaries.

The diameter of the full cells is about 3-4m. They differ oval or round disk-like shape. Surface in a calm state is smooth. But when they come into contact with other bodies or an alien surface, threadlike processes immediately appear on the corpuscles, which give them a stellate shape.

Structure

In addition to the information that the averagethe life expectancy of platelets is about 7 days, it is important to know that in each cell can distinguish three layers. The peripheral zone consists of an overmembrane zone, the purpose of which is to activate the platelet. Following it, there is a membrane responsible for adequate and timely reaction of the cell itself and clotting factors. It contains the so-called phospholipid matrix. It forms coagulation complexes. It is also responsible for the aggregation and adhesion of platelets.

In the zone of sol-gel are mitochondria. Also there pass special channels that connect this layer with the outer membrane. The sol-gel zone contains thrombosteine, which is responsible for the disk-like shape of the plates.

Separately experts allocate a site of organelles. It contains 4 types of granules. It is in them that the process of accumulation of coagulation factors takes place. They function throughout the entire time, regardless of the fact that the life span of platelets is 5-12 days.

This division of the zones can be considered by repeatedly magnifying the cells under a microscope.

Life cycle of platelets

After the blood plates separated from themegakaryocyte, they enter the bloodstream. It is worth noting that thrombopoietin is involved in the regulation of this process. It is necessary for the normal formation of platelets and the full maturation of the cytoplasm of megakaryocytes.

Approximately 1/3 of the totalis deposited in the spleen. The remaining 70% circulate in the total blood flow. This depot is created in the spleen due to the fact that they move forward in this organ slowly enough. The process takes about 8 minutes. As a result, platelets are released into the total bloodstream and rush to the place where they are needed. All problems with the spleen are immediately displayed on the number of these blood plates. True, this does not affect the life span of platelets, but only changes their number in the blood. So, with its removal of the spleen, their concentration will be much higher. But with splenomegaly (an increase in this organ), these small cells move through it more slowly. This leads to a significant decrease in their amount in the blood.

It is worth noting that it participates in the processesrestoration of blood vessels, tissue healing and blood clotting are only a small part of the platelets. The rest die in the bone marrow, spleen and liver under the influence of macrophages.

</ p>