Been reading Linne och Ringsrud 7th edition. Scanned relevant paragraphs. Cannot grasp this, the book seems contradictory regarding
factor IX in the external path.
I've scanned two paragraphs and two images from the book chronologically. Book says:
Factor VII is activated to its VIIa form in the presence of ionized calcium (factor IV) and tissue thromboplastin (factor III). Factor VIIa activates coagulation factor IX to IXa, which in turn activates factor X to Xa. Thromboplastin is released from the injured wall of the blood vessel. Only activated factor VII is needed in the extrinsic pathway, bypassing factors XII, XI, IX, and VIII ...
So first it states
factor IX is part of the external path ("
Factor VIIa activates coagulation factor IX to IXa") and then immediately afterward it states that
factor IX is bypassed in the external path ? Wut?
~
Second quandary. What does the arrow in the first picture from activated
factor VIIa connecting to
factor IX activation mean exactly: Does it mean that:
1) activated
factor VII (VIIa) is required to activate
factor IX (along with calcium
Ca++ and
factor XIa)? or does it mean
2) activated
factor VII (VIIa) can activate
factor IX by itself independent of
Ca++ and
factor XIa?
Begin scanned textbook text and images:
(I'm not happy with the images showing up so small, in the source they're large)
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