Question is incomplete, the complete question is as follows :
Clotting begins when a _________ occurs in a blood vessel wall. Almost immediately, _______ cling to the blood vessel wall and release _____________ which helps to decrease blood loss by constricting the vessel. __________ is also released by damaged cells in the area. This chemical substance causes ________to be converted to ____________. Once present, thrombin acts as an enzyme to atatch ___________molecules together to form long, threadlike strands of _________, which then traps ____________ flowing by in the blood.
Answer:
Clotting begins when a <u>BREAK</u> occurs in a blood vessel wall. Almost immediately, <u>PLATELETS</u> cling to the blood vessel wall and release <u>SEROTONIN</u>, which helps to decrease blood loss by constricting the vessel. <u>THROMBOPLASTIN</u> is also released by damaged cells in the area. This chemical substance causes <u>PROTHROMBIN</u> to be converted to <u>THROMBIN</u>. Once present, thrombin acts as an enzyme to attach <u>FIBRINOGEN</u> molecules together to form long, threadlike strands of <u>FIBRIN</u>, which then traps<u> ERYTHROCYTES </u>flowing by in the blood.