CIE IGCSE Biology: 复习笔记：9.1.17 Conversion of Fibrinogen: Extended

• Platelets are fragments of cells which are involved in blood clotting and forming scabs where skin has been cut or punctured
• Blood clotting prevents continued / significant blood loss from wounds
• Scab formation seals the wound with an insoluble patch that prevents entry of microorganisms that could cause infection
• It remains in place until new skin has grown underneath it, sealing the skin again

How the blood clots

• When the skin is broken (i.e. there is a wound) platelets arrive to stop the bleeding
• A series of reactions occur within the blood plasma
• Platelets release chemicals that cause soluble fibrinogen proteins to convert into insoluble fibrin and form an insoluble mesh across the wound, trapping red blood cells and therefore forming a clot
• The clot eventually dries and develops into a scab to protect the wound from bacteria entering

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