Assertion : Blood coagulate in uninjured blood vessels. Reason : Uninjured blood vessels release an anticoagulant heparin.
Assertion : Blood coagulate in uninjured blood vessels.
Reason : Uninjured blood vessels release an anticoagulant heparin.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not correct explanation of A
(c) A is true but R is false
(d) A and R are false
1 Answers
The correct option is (d) A and R are false.
Explanation:
Whet 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 tissues or platelets also release coagulation promoting substances called thromboplastins which help in the formation of an enzyme prothrombinase . This enzyme activates inactive protein prothrombin to active thrombin which further promotes the coagulation process. Blood normally contains an anticoagulant heparin which is released from mast cell granules that prevents tire 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.