blood clotting

• blood clotting helps minimise blood loss and prevents the entry of infecting microorganisms
• during vasoconstriction muscles in arteries constrict immediately to reduce blood flow
• (Platelet plug)

  Smooth internal walls become rough when damaged which allows platelets to stick to walls
• (Platelets plug)

  Sticking platelets attract others which builds a platelet plug, reducing blood loss
• (Platelets plug)

  Platelets release substance that act as vasoconstrictors, enhancing and prolonging constriction
• Coagulation or blood clotting is the process of blood becoming gel-like
• coagulation is a complex process involving a large number of clotting factors which results in the formation of threads of insoluble protein called fibrin
• clotting factors - chemical substances in blood plasma that allow blood to clot
• Fibrin threads form a mesh which traps blood cells, platelets and plasma, the mesh along with the trapped materials is the clot or thrombus
• Fibrin threads stick to the damaged vessel and holds the clot in position
• serum is squeezed out as clot retraction occurs
• serum is the protein-rich fluid that separates out when blood coagulates
• Clot dries, forming a scab over wound which prevents entry of microorganisms
• clot retraction is the contraction of the network of threads, becoming denser and stronger, pulling the edges of the blood vessel together