Assertion: Blood coagulates in injured blood vessels.
Reason: Uninjured blood vessels release an anticoagulant heparin.
Assertion: Blood coagulates in injured blood vessels.
Reason: Uninjured blood vessels release an anticoagulant heparin.
The correct option is D Both assertion and reason are false.
When a blood vessel gets injured, blood platelets get clumped at the injured spot and release certain chemicals called platelet factors, which promote blood coagulation. Injured tissue or platelets also release coagulation promoting substances called thromboplastins which help in the formation of an enzyme prothrombinase. This enzyme activates inactive protein prothrombin into active thrombin which further promotes blood coagulation. Blood normally contains an anticoagulant called heparin which is released from the mast cell granules that prevents the activation of prothrombin in uninjured blood vessels. Blood also contains antithrombin which inhibits any thrombin formed accidentally. Moreover, uninjured tissues do not release thromboplastins, hence blood does not coagulate in uninjured blood vessels.
Both assertion and reason are false.
When a blood vessel gets injured, blood platelets get clumped at the injured spot and release certain chemicals called platelet factors, which promote blood coagulation. Injured tissue or platelets also release coagulation promoting substances called thromboplastins which help in the formation of an enzyme prothrombinase. This enzyme activates inactive protein prothrombin into active thrombin which further promotes blood coagulation. Blood normally contains an anticoagulant called heparin which is released from the mast cell granules that prevents the activation of prothrombin in uninjured blood vessels. Blood also contains antithrombin which inhibits any thrombin formed accidentally. Moreover, uninjured tissues do not release thromboplastins, hence blood does not coagulate in uninjured blood vessels.
