Li Qiong, Department of Clinical Laboratory, Characteristic Medical Center (formerly 306 Hospital).
Edited by Liu Yan/Cui Yan, Medical Science Popularization Center
Platelets are small pieces of cytoplasm shed from the cytoplasm of mature megakaryocytes, which together with white blood cells and red blood cells constitute the three major systems in the blood, and are one of the important components of blood. The volume of platelets is much smaller than that of red blood cells and white blood cells, and the size is different, and its average diameter is about 2~4 microns. Platelets vary in morphology, ranging from disc-shaped or olive-shaped, fusiform or irregular, and protrude pseudopodia when exposed to external stimuli. The normal reference value of platelet count is 125~320×10⁹/L, too low and too high will affect our health.
The main physiological functions of platelets
(1) Accelerated coagulation: When the blood vessel is damaged or ruptured, the platelets are stimulated, and the deformation and surface adhesion will be enhanced, and the clump will be aggregated, and at the same time, the substances related to coagulation will be released, and under the action of coagulation factor III., a clot will be formed at the damaged part of the blood vessel to achieve coagulation.
(2) Promote hemostasis: platelets release serotonin, catecholamines and other vasoconstrictive substances can make the damaged blood vessels shrink and close to varying degrees, and the blood flow in the blood vessels is relatively reduced, thereby playing a role in hemostasis.
(3) Repair of broken blood vessels: platelets have the effect of protecting the vascular endothelium, participating in endothelial repair, and preventing atherosclerosis. Platelets release lectins, which form fibrin under the action of agglutination source and fibrinogen, and fibrin coagulates to form fibers, thus playing a role in repairing broken blood vessels.
(4) Protection of vascular endothelium: Platelets have the effect of nourishing and supporting capillary endothelial cells, as well as reducing capillary fragility.
A common cause of low platelets
Platelets below 125×109/L can be called thrombocytopenia, when the platelets are less than 50×109/L, there may be bleeding tendency, when platelets are less than 30×109/L, there may be extensive bleeding tendency, bleeding after trauma, when platelets are less than 10×109/L, spontaneous bleeding will occur, which can be life-threatening and requires urgent treatment.
(1) Thrombocytogenesis: such as aplastic anemia, megaloblastic anemia, myelofibrosis, leukemia and other bone marrow diseases.
(2) Excessive platelet destruction: other viral infections such as primary thrombocytopenic purpura, drug allergy, hepatitis C virus and human immunodeficiency virus can cause thrombocytopenia.
(3) Abnormal platelet distribution: liver cirrhosis, bone marrow fibrosis and other reasons cause hypersplenism, and the enlarged spleen will capture platelets, resulting in a decrease in the number of platelets in the blood.
(4) Radiotherapy, chemotherapy and some drugs (such as heparin, certain antibiotics, anticancer drugs, etc.) can also cause thrombocytopenia.
Pseudothrombocytopenia
Pseudothrombocytopenia is associated with poor blood collection, use of anticoagulants, hyperlipidemia, and condensation. Among them, the most common is ethylenediaminetetraethylene (EDTA)-dependent pseudothrombocytopenia, which is due to the sensitivity of platelets to the anticoagulant EDTA in some people, which induces special proteins in platelets to aggregate platelets, resulting in a falsely low platelet count. The solution is usually to use a diluent that does not contain an anticoagulant or to replace it with another type of anticoagulant.
Therefore, when thrombocytopenia is detected on the first test, we should actively look for the cause, and if there are no corresponding symptoms and signs, it may be pseudothrombocytopenia.
In short, thrombocytopenia is a relatively common clinical symptom, we must further examine it in time, distinguish the true from the false, if there is bleeding tendency such as skin bleeding spots, bruising, gingival bleeding, etc., you should go to the hospital in time, and actively cooperate with the doctor for examination and treatment to prevent the aggravation of the condition.
(The picture comes from the Internet)