Platelet facts for kids
A platelet is a cell fragment that circulates in the blood. Platelets are involved in hemostasis through the making of blood clots. A low platelet count (number of platelets in the blood) can cause a person to bleed without their blood clotting (making scabs). A high platelet count can increase the risk of thrombosis (blood clots inside blood vessels), which stops blood from flowing properly.
Anatomy
Platelets do not have a cell nucleus. They are disc-shaped, and are 1.5 to 3 micrometers in diameter. The body does not have a lot of platelets, so they can all be used up quickly. They contain RNA, a canalicular system, and several different types of granules; lysosomes (containing acid hydrolases), dense bodies (containing ADP, ATP serotonin and calcium) and alpha granules (containing fibrinogen, factor V, vitronectin, thrombospondin and von Willebrand factor), the contents of which are released when the platelet is activated.
Images for kids
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The ligands, denoted by letter L, signal for platelets (P) to migrate towards the wound (Site A). As more platelets gather around the opening, they produce more ligands to amplify the response. The platelets congregate around the wound in order to create a cap to stop blood flow out of the tissue.
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Platelets derive from totipotent marrow stem cells.
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Platelets extruded from megakaryocytes
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Scanning electron micrograph of blood cells. From left to right: human erythrocyte, activated platelet, leukocyte.
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Diagram of the structure of a platelet showing the granules
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Platelet clumps in a blood smear
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On for example optical densitometry, a first and second wave of platelet aggregation is seen, in this case for an ADP-initiated aggregation. Data suggest that ADP activates the PI3K/Akt pathway during the first wave of aggregation, leading to thrombin generation and PAR‐1 activation, which evokes the second wave of aggregation.
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Platelets collected by using apheresis at an American Red Cross donation center
See also
In Spanish: Plaqueta para niños
