Clotting

1) Damage to blood vessel 2) Vasoconstriction to reduce blood flow 3) Thrombocytes attach to wound (Plug formation - release vasoconstrictors for further vasoconstriction) 4) Clotting commences formation of fibrinogen net (Thrombin system) 5) Clot retraction to from scab 6) Clot breakdown

• Walls of blood are usually very smooth - Damage to vessels creates rough surfaces in lumen which thrombocytes (platelets) stick to

Walls of the blood vessels constrict

• Thrombocytes stick to the damaged area and attract more thrombocytes creating a plug • For small tares in capillaries this is enough to stop bleeding

• Thrrombocytes release vasoconstrictors that make the walls constrict more and for a longer time, further reducing blood flow to the damaged site

• forms over the site of a wound to stop the bleeding • if a clot forms inside a blood vessel it forms a thrombus • if a thrombus breaks loose it can lodge in a vital blood vessel in brain/heart and cause a stroke/heart attack

1) Following damage to a blood vessel, blood platelets and the injured cells release thromboplastin 2) Thromboplastin interacts with CA + prothhrombin (an inactive plasma protein) to form thombin 3) Thrombin converts finbrinagen (inactive plastic protein) to long stretchy fibres of fibrin 4) The fibrin fibres form a mesh at the site of the wound, which traps platelets and blood cells 5) Within a few minutes, the clot starts to contract which pushes the edges of the broken blood vessel together

• Thrombin + fibrinogen = fibrin - Fibrin + blood vessels = clot

• The threads in the clots contract, pulling the damaged vessels apart • The fluid in the clot (serum) is forced out, drying the clot • Serum= yellow, clear liquid that comes from the clot