39 - coagulation series 5 of 7

KYJ39- Intrinsic Coagulation part 5.

I was over viewing the coagulation cascade that we have covered in our first 4 episodes, and also the process yet to cover, when it dawned on me that coagulation is much like the startup sequence of an aircraft.  Flick that switch, twist that knob, push this button, then shift that lever.  It happens with all the precision of a skilled pilot.

The intrinsic (contact activation) pathway started with Factor 12 (FXII or Hageman Factor) becoming activated by a blood contaminant, bacteria or tissue injury.

The process in now underway.  Activated Hageman factor (FXIIa) catalyses the activation of factor XI (Plasma Thromboplastin).  There is not much to
Be said for FXI, except that it is another liver produced protein which circulates in plasma as a dormant sleeper, and woken up by activation of Hageman Factor.

Once activated Thromboplastin, switches on factor 9 (Factor IX) also called Christmas Factor.   We discussed this briefly in an earlier post (KYJ 28) if you missed it click to http://KnowingYourJargon.blogspot.com

Now Factor 9 is activated which activates Factor 10.

12 - 12a - 11 - 11a - 9 - 9a - 10 - 10a.

Do you get a sense that one inactive protein is activated, which switches on or activates the next in a "dominoes" effect like cascade. It is literally a chain reaction.

Now we have covered all the coagulation factors that are called Serine proteases. This means that they act as enzymes (*ases) that activate other chemical reactions.

This post brings the Intrinsic and extrinsic pathway to a common point- Factor X.

The X Factor is therefore the start of what is called the Common Pathway.

Let's summarise:
Injured vessel releases tissue factor (F3)
F3 converts F7 to activate F10.

Or
Tissue injury allows F12 to activate, converting F11, converting F9 activating F10.

Now the pathway to clotting is the same.
Factor 10 activates F2 (prothrombin to Thrombin),
which activates Factor 1 (fibrinogen into Fibrin clots)
...
The coagulation factors that have not been covered yet include Factors 5, 8, 13, and the proteins S, C, Z and of course Calcium (Factor 4).

Stay tuned and we will fill in the gaps in the next episode.