Platelets - what they are for the body? - Structure and Form

What platelets and their structure

Platelets (blood plates, plaques Bitstsotsero) - a nuclear-free education, surrounded by a membrane, one of the main types of blood cells, which are fragments of the bone marrow - megakaryocytes.

Platelets are formed in the bone marrow from the cytoplasm otshnurovyvaetsya megakaryocyte platelet and enters the blood. Ripening of platelets is an average of 8 days, the duration of their stay in the blood stream - from 8 to 11 days. Normally the blood contains 200 - 400 thousand. Platelets in 1 ml of blood.

Normal platelets have a diameter of 3-4 mm, small forms (microforms) - smaller and larger (macro-) - a larger diameter. The blood platelets are oval or round in shape with a smooth surface. In contact with a foreign surface platelets become activated and acquire a star-shaped with filiform appendages (pseudopodia).

The platelet is divided into four zones:

• nadmembranny layer (glycocalyx) - it carries platelet activation;
• membrane - it interacts with platelet coagulation factors; at the inner layer of the membrane has a system of channels connecting the membrane surface to the cytoplasm;
• gel zone (matrix) - contains the mitochondria - the constant inclusion of all plant and animal cells that produce pellets and involved in the synthesis taking place in the cells;
• organelles zone - contains four types of pellets, collecting blood clotting factors, some of the elements comprising the mitochondria, vesicles, and the contrast of grain tubule.

The platelets contain various substances that accelerate the gradual conversion of the inactive clotting factors in the active.

Platelets contain a large amount of protein (protein) and amino acids (the components of proteins), a few less fat (lipid), a small amount of ash, lipoprotein complexes, glycogen (reserve carbohydrates - a source of energy required for the cells) in the form of granules of various sizes, ATP sodium, calcium, potassium, magnesium, copper, iron, manganese and some other components.

Forms of platelets

Depending on the degree of maturity of the following forms of platelets:

• mature forms (in healthy individuals they make up 80-95%), they are distinguished outer pale blue zone (gialomer) and a central grit (granulomer); in contact with foreign surface gialomer forms on platelet surface appendages of various size and shape;
• young (immature) shape - they have a large shape compared with mature platelets; appearance of these forms in a large amount shows the increased bone marrow, often associated with blood loss;
• the old forms - different forms of education with a narrow bezel and a large number of granules and vacuoles; their occurrence in a large amount indicates the presence of cancer Malignant tumor: cells are mad ;
• forms of stimulation - large size of the different forms of education, resulting in violation of platelets by megakaryocytes otshnurovki; the emergence of forms of irritation may indicate blood diseases Diseases of the blood - always seriously ;
• degenerative platelets - platelets are small changes, their presence also constitutes a violation of hematopoiesis.

Major physiological properties of platelets

The main physiological properties of platelets is the tendency of adhesion (adhesion to solid surfaces) and aggregation (bonding or unification process individual platelets in a single system) and adsorption (deposition) on the surface of blood coagulation factors contained in the liquid portion of blood - plasma and transport with blood.

Platelets are usually located on the periphery of blood flow closer to the walls of blood vessels. Here they interact with cells of the intima, which stimulates their hemostatics function.

If the damage of the blood vessel walls of its various components stimulated aggregation (bonding) and platelet release reaction: the release of platelet granules and formation of a power amplifier of platelet aggregation thromboxane A2. Reaction release may also occur under the influence of allergic reactions Allergic reactions: how to understand why you tickle in the throat Viruses, bacteria and so on. During the reaction, liberation of platelets secrete substances such as ATP, histamine, epinephrine, serotonin, enzymes and some blood coagulation factors. From the released platelet granule calcium, which reshapes the platelet release reaction stimulates and activates the bonding irreversible platelet thrombus formation.

Changing the number of blood platelets

Increasing the number of platelets (thrombocytosis) may occur under certain blood diseases, inflammatory diseases, acute infections, after removal of the spleen.

Reducing the number of platelets (thrombocytopenia) occurs during deceleration formation of megakaryocytes in the bone marrow (e.g., acute leukemia Leukemia - more not a sentence , Certain types of anemia and so on), with the accumulation of platelets in the spleen (liver cirrhosis), increased breakdown of platelets (systemic lupus erythematosus), platelet damage caused by blood coagulation factor thrombin (at infection blood) and so on.

Platelets - an important element of the blood they take as a direct or indirect participation in the prevention of large blood loss.

Galina Romanenko