Answer:
(a) Certain
factors released by the tissues at the site of injury can initiate coagulation
process.
Calcium ions and
platelet factor act in the first step of coagulation which is as follows
(i) At the
site of an injury, the blood platelets disintegrate and release a phospholipid,
called platelet factor 3 (platelet thromboplastin)
(ii)Injured
tissues also release a lipoprotein factor called thromboplastin.
(iii) These
two factor combine with calcium ions
and certain proteins of the blood plasma to form an enzyme called
pro-thrombinase.
(iv)Prothrombiminase
catalyzes prothrombin into active protein called thrombin.
(v) Thrombin
further converts inactive fibrinogens into fibrin in the blood plasma.
(vi) Then
the long fibres of fibrin form a dense network upon wound and trap blood corpuscles
RBCs, WBCs and platelets) to form a clot.
And the other
options are wrong.
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