Image from a light microscope (500 ×) from a Giemsa-stained peripheral blood smear showing platelets (small purple dots) surrounded by red blood cells (large gray circular structures)
Details
Precursor
Megakaryocytes
Function
Formation of blood clots; prevention of bleeding
Identifiers
Latin
thrombocytus
MeSH
D001792
FMA
62851
Anatomical terms of microanatomy
[edit on Wikidata]
Platelets or thrombocytes (from Ancient Greek θρόμβος (thrómbos) 'clot', and κύτος (kútos) 'cell') are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby initiating a blood clot.[1] Platelets have no cell nucleus; they are fragments of cytoplasm derived from the megakaryocytes[2] of the bone marrow or lung,[3] which then enter the circulation. Platelets are found only in mammals, whereas in other vertebrates (e.g. birds, amphibians), thrombocytes circulate as intact mononuclear cells.[4]: 3
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.
One major function of platelets is to contribute to hemostasis: the process of stopping bleeding at the site of interrupted endothelium. They gather at the site and, unless the interruption is physically too large, they plug the hole. First, platelets attach to substances outside the interrupted endothelium: adhesion. Second, they change shape, turn on receptors and secrete chemical messengers: activation. Third, they connect to each other through receptor bridges: aggregation.[5] Formation of this platelet plug (primary hemostasis) is associated with activation of the coagulation cascade, with resultant fibrin deposition and linking (secondary hemostasis). These processes may overlap: the spectrum is from a predominantly platelet plug, or "white clot" to a predominantly fibrin, or "red clot" or the more typical mixture. Some would add the subsequent retraction and platelet inhibition as fourth and fifth steps to the completion of the process[6] and still others would add a sixth step, wound repair. Platelets also participate in both innate[7] and adaptive[8] intravascular immune responses.
In addition to facilitating the clotting process, platelets contain cytokines and growth factors which can promote wound healing and regeneration of damaged tissues.[9][10]
^Laki K (December 1972). "Our ancient heritage in blood clotting and some of its consequences". Annals of the New York Academy of Sciences. 202 (1): 297–307. Bibcode:1972NYASA.202..297L. doi:10.1111/j.1749-6632.1972.tb16342.x. PMID 4508929. S2CID 45051688.
^Machlus KR, Thon JN, Italiano JE (April 2014). "Interpreting the developmental dance of the megakaryocyte: a review of the cellular and molecular processes mediating platelet formation". British Journal of Haematology. 165 (2): 227–236. doi:10.1111/bjh.12758. PMID 24499183. S2CID 42595581.
^Lefrançais, Emma; Ortiz-Muñoz, Guadalupe; Caudrillier, Axelle; Mallavia, Beñat; Liu, Fengchun; Sayah, David M.; Thornton, Emily E.; Headley, Mark B.; David, Tovo; Coughlin, Shaun R.; Krummel, Matthew F. (April 2017). "The lung is a site of platelet biogenesis and a reservoir for haematopoietic progenitors". Nature. 544 (7648): 105–109. Bibcode:2017Natur.544..105L. doi:10.1038/nature21706. ISSN 1476-4687. PMC 5663284. PMID 28329764.
^Cite error: The named reference Michelson was invoked but never defined (see the help page).
^Berridge, Michael J. (1 October 2014). "Module 11: Cell Stress, Inflammatory Responses and Cell Death" (PDF). Cell Signalling Biology. Vol. 6. Portland Press. pp. 11-1–11-30. doi:10.1042/csb0001011 (inactive 2024-02-11).{{cite book}}: CS1 maint: DOI inactive as of February 2024 (link)
^Gaertner F, Massberg S (December 2016). "Blood coagulation in immunothrombosis-At the frontline of intravascular immunity". Seminars in Immunology. 28 (6): 561–569. doi:10.1016/j.smim.2016.10.010. PMID 27866916.
^Hampton T (April 2018). "Platelets' Role in Adaptive Immunity May Contribute to Sepsis and Shock". JAMA. 319 (13): 1311–1312. doi:10.1001/jama.2017.12859. PMID 29614158.
^Cecerska-Heryć E, Goszka M, Dołęgowska B (2022). "Applications of the regenerative capacity of platelets in modern medicine". Cytokine & Growth Factor Reviews. 64: 84–94. doi:10.1016/j.cytogfr.2021.11.003. PMID 34924312.
^Xu J, Gou L, Qiu S (2020). "Platelet-rich plasma and regenerative dentistry". Australian Dental Journal. 65 (2): 131–142. doi:10.1111/adj.12754. PMC 7384010. PMID 32145082.
Platelets or thrombocytes (from Ancient Greek θρόμβος (thrómbos) 'clot', and κύτος (kútos) 'cell') are a component of blood whose function (along with...
characterized by abnormally low levels of platelets (also known as thrombocytes) in the blood. Low levels of platelets in turn may lead to prolonged or excessive...
process of coagulation involves activation, adhesion and aggregation of platelets, as well as deposition and maturation of fibrin. Coagulation begins almost...
Giant platelet disorders, also known as macrothrombocytopenia, are rare disorders featuring abnormally large platelets, thrombocytopenia and a tendency...
Platelet transfusion, also known as platelet concentrate, is used to prevent or treat bleeding in people with either a low platelet count or poor platelet...
commonly called platelets, a component of blood involved in blood clotting. The term specifically refers to the method of collecting the platelets, which is...
known as a platelet agglutination inhibitor or platelet aggregation inhibitor, is a member of a class of pharmaceuticals that decrease platelet aggregation...
thrombocytopenia, is a type of thrombocytopenic purpura characterized by a low platelet count in the absence of other causes, and accompanied by a red-purple rash...
The platelet plug, also known as the hemostatic plug or platelet thrombus, is an aggregation of platelets formed during early stages of hemostasis in...
Mean platelet volume (MPV) is a machine-calculated measurement of the average size of platelets found in blood and is typically included in blood tests...
Platelet adhesiveness is the adhesion of platelets to other structures. It can be contrasted with platelet aggregation,[citation needed] which refers to...
Human platelet antigens (HPA) are polymorphisms in platelet antigens. These can stimulate production of alloantibodies (that is, antibodies against other...
used while testing the blood sample causes clumping of platelets which mimics a low platelet count. The phenomenon has first been reported in 1969. It...
Platelet transfusion refractoriness is the repeated failure to achieve the desired level of blood platelets in a patient following a platelet transfusion...
Platelet swirling is a noninvasive method for testing the quality of platelet-rich plasma (PRP). Platelet swirling is caused by light diffraction due...
Platelet factor 4 (PF4) is a small cytokine belonging to the CXC chemokine family that is also known as chemokine (C-X-C motif) ligand 4 (CXCL4) . This...
Alpha granules, (α-granules) also known as platelet alpha-granules are a cellular component of platelets. Platelets contain different types of granules that...
Harris platelet syndrome, previously known as asymptomatic constitutional macrothrombocytopenia, is the most common inherited giant platelet disorder...
von Willebrand factor (VWF), a multimeric protein that is required for platelet adhesion. It is known to affect several breeds of dogs as well as humans...
is a large bone marrow cell with a lobated nucleus that produces blood platelets (thrombocytes), which are necessary for normal clotting. In humans, megakaryocytes...
Human platelet lysate (or hPL) is a substitute supplement for fetal bovine serum (FBS) in experimental and clinical cell culture. It is a turbid, light-yellow...
Platelet storage pool deficiency is a type of coagulopathy characterized by defects in the granules in platelets, particularly a lack of granular non-metabolic...
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