Isakhiwo kanye Nomsebenzi Wama-Platelet
Ama-platelet, noma ama-platelet egazi, ayizingcezu ezincane zamaseli ezitholakala egazini futhi ezihilelekile enqubweni yokujiya kwegazi (i-hemostasis). Ayingxenye ebalulekile yesistimu yokujikeleza kwegazi yomuntu, edlala indima ebalulekile ekumiseni ukopha nasekuqaliseni ukuphulukiswa kwenxeba. Kulesi sihloko, sizohlola isakhiwo kanye nomsebenzi wama-platelet ngokujulile, kanye nokubaluleka kwawo ekugcineni impilo yomzimba wonke.
Umsuka Nokukhiqizwa Kwama-Platelet
Ama-platelet avela kumaseli amakhulu abizwa ngokuthi ama-megakaryocytes emnkantsheni wamathambo. Ama-megakaryocytes angamaseli amakhulu kakhulu futhi ayinkimbinkimbi, anobubanzi obufinyelela kuma-micrometer ayi-100. Lawa maseli akhiqiza ama-platelet ngokukhulula izingcezu ezincane ze-cytoplasm yawo egazini. Le nqubo ilawulwa yizici ezahlukene zokukhula nama-hormone, okuhlanganisa i-thrombopoietin, ekhuthaza ukukhiqizwa nokuvuthwa kwama-megakaryocyte.
Uma sekwenziwe, ama-platelet ajikeleza egazini cishe izinsuku eziyi-7 kuya kweziyi-10 ngaphambi kokuba abhujiswe uhlelo lwe-reticuloendothelial, ikakhulukazi esinqeni nasesibindini. Ngokuvamile, inani lama-platelet egazini lisukela ku-150.000 kuya ku-450.000 nge-microliter ngayinye. Inani eliphansi lama-platelet libizwa ngokuthi i-thrombocytopenia, kanti inani eliphezulu lama-platelet libizwa ngokuthi i-thrombocytosis.
Isakhiwo sePlatelet
Ama-platelet anesakhiwo esiyingqayizivele nesiyinkimbinkimbi naphezu kobukhulu bawo obuncane, alinganiselwa phakathi kwama-micrometer amabili nama-3 ububanzi. Isakhiwo sawo siqukethe izingxenye eziningana eziyinhloko:
1. I-Plasma Membrane: Ingqimba yangaphandle yama-platelet, equkethe ama-receptor ama-molecule ahlukahlukene okubonisa izimpawu, kufaka phakathi i-collagen, i-fibrinogen, kanye nezinto zokukhula. Le membrane iphinde isekele ama-glycoprotein adlala indima ebalulekile ekuhlanganisweni kwama-platelet kanye nokunamathela ezindongeni zemithambo yegazi ezilimele.
2. I-Cytoplasm: Ingxenye engaphakathi yeplatelet equkethe ama-organelle nezakhiwo ezahlukahlukene, okuhlanganisa i-mitochondria, i-lysosomes, kanye nama-granules. Lawa ma-granules aqukethe ama-alpha granules, aqukethe amaprotheni okujiya njenge-fibrinogen kanye nezinto zokukhula, kanye nama-dens granules, aqukethe ama-molecule afana ne-ADP kanye ne-calcium adlala indima ekusebenzeni kweplatelet.
3. I-Cytoskeleton: Inethiwekhi yamaprotheni esakhiwo ngaphakathi kwama-platelet ahlinzeka ngesimo kanye nokusekelwa kwemishini. Izinto eziyinhloko zalesi si-cytoskeleton zifaka i-actin nama-microtubules, avumela ama-platelet ukuthi ashintshe isimo sawo ngesikhathi sokusebenza kanye nokuhlangana.
4. Uhlelo Lwesiteshi Esivulekile kanye Nohlelo Lwe-Tubular Oluqinile: Izakhiwo ze-membrane yangaphakathi ezisebenza ekugcineni nasekukhululweni kwama-molecule okubonisa izimpawu. Uhlelo lwesiteshi esivulekile luxhumana nengaphandle leseli futhi lusiza ekukhululweni kokuqukethwe kwe-granule, kuyilapho uhlelo lwe-tubule oluqinile ludlala indima ekugcinweni kwe-calcium kanye nokulawulwa kwamazinga e-calcium angaphakathi kweseli.
Umsebenzi we-Platelet
Ama-platelet anemisebenzi eminingana eyinhloko ehlobene nokususwa kwegazi kanye nokuphulukiswa kwamanxeba:
1. Ukwakheka Kweplaki Yama-Plutelet
Uma umthambo wegazi ulimele, i-collagen kanye ne-tissue factor evela ku-extracellular matrix eveziwe kusebenze ngokushesha ama-platelet. Ama-activated platelet ashintsha isimo, anamathela, futhi anamathele odongeni lomthambo olimele. Aqala futhi ukukhipha okuqukethwe yi-granules yawo, okuhlanganisa nezinto ezibangela ukujiya kanye namanye ama-syllable molecules adonsela ama-platelet amaningi endaweni yokulimala.
Le nqubo iholela ekwakhekeni kwe-platelet plug yokuqala evimba ukopha okwesikhashana. Lesi yisinyathelo sokuqala se-hemostasis eyinhloko, esivimbela ukulahleka kwegazi ngokweqile kuze kube yilapho izindlela zesibili zokugaya igazi zingakha i-clot eqinile.
2. Ukukhishwa Kwabaxhumanisi Bekhemikhali
Uma kusebenze, ama-platelet akhipha ama-chemical mediator ahlukahlukene kuma-granule awo. Ama-alpha granule akhipha amaprotheni afana ne-fibrinogen, i-platelet growth factor (PDGF), ama-coagulation factor, i-kininogen, kanye ne-vWf (von Willebrand factor), anegalelo ekuhlanganisweni kwama-platelet kanye nokuzinza kwama-platelet plug. Ama-dens granule akhipha ama-molecule amancane njenge-ADP, i-ATP, i-serotonin, kanye ne-calcium, adlala indima ekuncipheni kwemithambo yegazi, adonsele ama-platelet amaningi endaweni yokulimala, kanye nokusebenza kwama-platelet okuqhubekayo.
Isibonelo, i-ADP ibopha i-P2Y12 receptor ebusweni be-platelet, okubangela ushintsho lwesimo se-platelet, okwandisa ukusondelana kwayo ne-fibrinogen, kanye nokuqinisa ukusebenzisana phakathi kwama-platelet, okuholela ekuhlanganeni okuqinile. I-calcium idlala indima ebalulekile ezinyathelweni ezahlukahlukene zokujiya, isiza ekwakheni ama-enzyme complexes ebusweni be-platelet.
3. Ukuqina Kwegazi Nokwakheka Kwe-Fibrin
Ngaphezu kokwakha i-platelet plug nokukhulula abaxhumanisi, ama-platelet akhuthaza ukwakheka kwe-fibrin, iphrotheni eqinisa futhi izinzise i-platelet plug. Ama-platelet asebenzayo ahlinzeka ngobuso obusiza ukusebenzisana kwezinto ezihlanganisa ukujiya ezindleleni zangaphakathi nezangaphandle, okuholela ekuguqulweni kwe-fibrinogen encibilikayo ibe yi-fibrin engancibiliki. I-Fibrin yakha inethiwekhi ebamba amangqamuzana abomvu egazi namanye amangqamuzana egazini, okwenza i-blood clot ezinzile.
4. Ukwelapha Amanxeba
Ngaphezu kwendima yazo ekuqhekekeni kwegazi, ama-platelet nawo anegalelo enkambisweni yokuphulukiswa kwenxeba. Izinto zokukhula ezikhishwa ama-platelet, njenge-PDGF, i-vascular endothelial growth factor (VEGF), kanye ne-transforming growth factor-beta (TGF-β), zikhuthaza ukwanda nokufuduka kwamaseli aye endaweni yenxeba, okuhlanganisa ama-fibroblast, amaseli e-endothelial, namaseli e-epithelial. Le nqubo isiza ekwakhekeni kwezicubu ezintsha kanye nemithambo yegazi (i-angiogenesis), okubalulekile ekwelapheni inxeba ngempumelelo.
Ukuphazamiseka Kweplatelet
Ukungasebenzi kahle noma ukungalingani kwenani lama-platelet kungabangela izinkinga ezahlukene zempilo:
– I-Thrombocytopenia: Ukubalwa kwama-platelet aphansi kungaholela ekuphumeni kwegazi ngokweqile okunzima ukukuqeda. Lesi simo singabangelwa yizici ezahlukahlukene, okuhlanganisa izifo ezizimele, izifo, noma imiphumela emibi yemithi.
– I-Thrombocytosis: Ukubalwa kwama-platelet aphezulu kungandisa ingozi yokwakheka kwamahlule egazi, okungaholela ekushayweni yisifo sohlangothi noma ekuhlaselweni yinhliziyo. Izimbangela zingafaka phakathi ukuphazamiseka kwe-myeloproliferative, ukusabela ekuthelelekeni noma ekuvuvukeni, noma ingxenye yesifo esingamahlalakhona.
– Ukungasebenzi Kahle Kwezinhlayiya: Izinhlayiya ezingasebenzi kahle, noma ngabe inani lazo lijwayelekile, zingabangela nezinkinga zokopha, njengakwezinye izifo zofuzo noma ngenxa yemithi ethile.
Isiphetho
Ama-platelet adlala indima ebalulekile ohlelweni lokujikeleza kwegazi kanye ne-hemostasis. Ayingxenye ebalulekile yendlela yokuzivikela yomzimba ekulweni nokopha futhi anemisebenzi eyengeziwe ekwelapheni amanxeba. Ukuqonda okwengeziwe ngama-platelet, kokubili ezimweni ezijwayelekile kanye nezifo, kubalulekile ekuvimbeleni nasekwelapheni izifo ezahlukahlukene zegazi. Ucwaningo luyaqhubeka nokuhlola izici ezahlukahlukene zama-platelet, okuhlanganisa amandla awo ekwelashweni kwezokwelapha kanye nokungenelela kwezokwelapha.
